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Title: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 12, 2014, 02:50:01 pm
------clipped from earlier post-------

I have been wrestling with are Safety grounds good or bad conundrum where even a guitar player with a GFCI protected amp can get killed by hot ground external to his protected amp via the good amp safety ground (It actually happens).

I have looked into mA level fuses and apparently they made from fairy farts since they are insanely expensive (probably a medical equipment thing).

I figure I could stack a N-ch and P-ch MOSFET in series turned on to make a ground path with around 10 ohms on resistance, that I could open up electronically when I sense X mA of ground path current. The <$2 parts cost is much more reasonable than the crazy medical equipment fuse cost.  But the catch 22 is I need a safe isolated power supply, so to add a transformer or lump pushes the cost way up... BUT a tired 9V battery will still make around 7V which should be enough to turn on the two MOSFETs.

I would be crazy to sell these because somebody would probably sue me, but I am tempted to build one to see if it works.

-----end clip------

OK As I get older I get a little crazier but I am not beyond sussing this out.

#1 I found one US company making and selling the cheap in-line GFCI that sells for less than $30 in Lowes hardware chain. I haven't taken it apart yet (it uses an odd security screw holding the plastic clamshell package together).

#2 thinking about it some more I don't like the tired battery idea, 7V is marginal for turing on the MOSFETS hard and a PIA to keep fresh.
  A) one alternative is to incorporate this into a guitar pedal that already has a 9V supply. The incremental cost is now in the <$2 ballpark. A friend of mine makes and sells guitar pedals so I may bounce this idea pff him.
  B) If we build this into a smart GFCI power strip maybe include a PS and relay. Clearly an order of magnitude more parts cost but nothing says disconnected ground like a relay.

#3 What are the anticipated fault conditions we want to protect against that a stock GFCI outlet does not already cover?
   A) And this is the big one a properly ground bonded guitar amp played by a musician who encounters a hot ground microphone. The fix for this is opening up the ground connection "and" turning off power to the guitar amp, just in case.
   B) RPBG... perhaps a non contact sensor could detect if the ground is hot... This might also trip if a floating ground is measuring hot, perhaps a small shunt could prevent the false positive. Perhaps it is OK to not work unless it detects at least some impedance at the ground and no significant voltage.
   c) other???

Any thoughts.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on December 12, 2014, 03:38:49 pm


#2 thinking about it some more I don't like the tired battery idea, 7V is marginal for turing on the MOSFETS hard and a PIA to keep fresh.
  A) one alternative is to incorporate this into a guitar pedal that already has a 9V supply. The incremental cost is now in the <$2 ballpark. A friend of mine makes and sells guitar pedals so I may bounce this idea pff him.
  B) If we build this into a smart GFCI power strip maybe include a PS and relay. Clearly an order of magnitude more parts cost but nothing says disconnected ground like a relay.

....Any thoughts.

JR
Build it into a Phantom powered DI ?? Still use the mic, but plug the lead through the "protected" DI. Many times I'll throw a DI on a guitar for backup if I am less than 100% confident his rig will make it through the night. Saved an embarased player more than once with this "trick"....
As a system owner/operator, I am more likely to "spread the protection" around than counting on (cheap-ass ::)) guitar players to protect themselves.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 12, 2014, 05:05:27 pm
Build it into a Phantom powered DI ?? Still use the mic, but plug the lead through the "protected" DI. Many times I'll throw a DI on a guitar for backup if I am less than 100% confident his rig will make it through the night. Saved an embarased player more than once with this "trick"....
As a system owner/operator, I am more likely to "spread the protection" around than counting on (cheap-ass ::)) guitar players to protect themselves.

My judgement is that it is easier to protect one guitar than tens of mic inputs, but this does argue for plastic mic handles and maybe even non-conductive mic screens.

I need to dig a little deeper into cost of low mA fuses. I guess a 10mA fuse which isn't as expensive as 2 mA or 5 mA fuses, in series with XLR pin 1 could still work with most phantom powered mics and probably not kill the average musician in case of an encounter with mains voltage. In theory a phantom input with both pin 2 and 3 shorted is more than 10 mA but that is not typical current draw. 10mA is higher than I like but not crazy, and better than nothing for PA guys who want to be proactive. .

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 12, 2014, 05:44:02 pm
JR,

Now I've not costed this idea out, nor even really looked at the math to know if this would work, so this is napkin engineering at it's finest. What if you put a DPST NO latching reed relay in series with the shield and hot of the guitar cable? These latching relays can be latched using a external permanent magnet, but unlatched with a relatively small current (DC, I think). Now, put a current transformer to monitor any 60 Hz AC current in the shield. In fact, run both the shield and signal conductor through the current transformer so it's only looking for current external to the guitar's signal. So would there be sufficient sensing voltage/current from the sensing transformer to directly trip and unlatch the relay, maybe with a diode to rectify it? Would this system be sensitive enough to trip at 10 mA fault current? If not, then something as simple as a 741 Op-Amp or other comparator IC to do the tripping, but that would need a battery or other power source which I'm not in love with. Now, once the latching relay trips, you could then push a button to move a permanent magnet close to the latching relay to reset it.

Again, don't beat on me if I've missed something by a few orders of magnitude or even thinking about this completely backwards, but I like the concept of this safety device being self powered, reset with a permanent magnet, opens up both the guitar shield and signal lines at the same time, and doesn't introduce any semiconductors into the guitar signal path to mess with their "sound".

Thoughts? Comments? Critiques?
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on December 12, 2014, 06:01:41 pm
   B) RPBG... perhaps a non contact sensor could detect if the ground is hot... This might also trip if a floating ground is measuring hot, perhaps a small shunt could prevent the false positive. Perhaps it is OK to not work unless it detects at least some impedance at the ground and no significant voltage.
   c) other???

Any thoughts.
I've been thinking of a smallish socket tester that includes an antenna. Connect some opamp/optocoupler to each pin on the mains socket. If the pin is hot then it will give us big noise on the opamp and we will be able to detect the level of each pin in the socket. A simple comparator should do the trick.

I think that the current transformer sounds like a great idea and I had similar thoughts as well.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 12, 2014, 06:20:48 pm
JR,

Now I've not costed this idea out, nor even really looked at the math to know if this would work, so this is napkin engineering at it's finest. What if you put a DPST NO latching reed relay in series with the shield and hot of the guitar cable? These latching relays can be latched using a external permanent magnet, but unlatched with a relatively small current (DC, I think).
This is definitely at the napkin stage so all ideas are game.

I am not familiar with the latching relay you can set with a magnet... sounds clever. My hypothetical relay was specified using a 10A ac power relay so if it was energized with mains voltage it would be sure to break the 120v circuit, the 200 V dc rating of your model might be marginal (I don't know whether DC is harder or easier than breaking AC, probably harder). I was thinking a normal non-latching relay for use with a power supply so when non-powered ground is normally open.   
Quote

Now, put a current transformer to monitor any 60 Hz AC current in the shield. In fact, run both the shield and signal conductor through the current transformer so it's only looking for current external to the guitar's signal. So would there be sufficient sensing voltage/current from the sensing transformer to directly trip and unlatch the relay, maybe with a diode to rectify it? Would this system be sensitive enough to trip at 10 mA fault current? If not, then something as simple as a 741 Op-Amp or other comparator IC to do the tripping, but that would need a battery or other power source which I'm not in love with. Now, once the latching relay trips, you could then push a button to move a permanent magnet close to the latching relay to reset it.
I need to look at these... with access to power and active sensing I can probably detect current with a modest DC series resistance and op amps.
Quote
Again, don't beat on me if I've missed something by a few orders of magnitude or even thinking about this completely backwards, but I like the concept of this safety device being self powered, reset with a permanent magnet, opens up both the guitar shield and signal lines at the same time, and doesn't introduce any semiconductors into the guitar signal path to mess with their "sound".
Yes the relay is harder to criticize.
Quote
Thoughts? Comments? Critiques?

I need to do some more homework.  The company I found who might be a candidate to make a special musician version also sells a patented LCDI (Leakage current detection and interruption)... I glanced at the patent (6,738,241,B1) and can't say that I get what it's good for, but these guys should know how to do what we want, as soon as we figure out what we want to do.

I do not see any smart detection of RPBG that I would like to build into a smart GFCI outlet strip... (open ground and mains if we detect voltage on the ground).

Their website does not sell direct but they make a bunch of GFCI strips and extension cords that look useful for back line as is. http://www.towermfg.com/gfci.htm (http://www.towermfg.com/gfci.htm)

Keep the ideas coming....

In my ideal world we could make a power strip that can't be fooled, without breaking the bank.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 12, 2014, 06:49:41 pm
I am not familiar with the latching relay you can set with a magnet... sounds clever. My hypothetical relay was specified using a 10A ac power relay so if it was energized with mains voltage it would be sure to break the 120v circuit, the 200 V dc rating of your model might be marginal (I don't know whether DC is harder or easier than breaking AC, probably harder). I was thinking a normal non-latching relay for use with a power supply so when non-powered ground is normally open. 

This latching reed relay is in the guitar signal line, not the AC power line. It would have to see 180 volts peak (in the USA / twice that in the UK) but essentially zero current since the megohm input on a guitar amp has perhaps micro-amps of actual audio signal. But it would have to absorb the fault current of a human (perhaps 100 mA) or even a guitar string on a hot mic (a few amperes maybe, until it trips open). I'm thinking of it as a self-power GFCI (Guitar-Fault-Circuit-Interrupter) which could be in a stomp box.

Yes, I know we're looking for something that doesn't require the musicians to add them into their signal chain, so perhaps a specialized backline AC power GFCI is the best solution. But I can't help but think that opening up the guitar signal cable is a good way to protect the guitarist from a "hot" mic as well as a "hot" chassis guitar amp. More to think about.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on December 12, 2014, 08:40:31 pm
But I can't help but think that opening up the guitar signal cable is a good way to protect the guitarist from a "hot" mic as well as a "hot" chassis guitar amp. More to think about.   

I can see the guitar forum thread now.  I would use the Sokol box but it colors my sound.

I know what you meen but if you use it with a 12AX7 input it is a very nice color.

No. If you use it at the input of your pedal board with a guitar with a active pickup you only get the slightest warming effect.  I actually like two of them to get the best sound.

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 12, 2014, 08:59:12 pm
This latching reed relay is in the guitar signal line, not the AC power line. It would have to see 180 volts peak (in the USA / twice that in the UK) but essentially zero current since the megohm input on a guitar amp has perhaps micro-amps of actual audio signal. But it would have to absorb the fault current of a human (perhaps 100 mA) or even a guitar string on a hot mic (a few amperes maybe, until it trips open). I'm thinking of it as a self-power GFCI (Guitar-Fault-Circuit-Interrupter) which could be in a stomp box.
I may be over engineering this but would like to do it once and be done (it's a small market) so ideally a solution for world voltages (i.e. 400V parts).

The voltage/current I am concerned about is hot ground mic to grounded guitar amp... which could be lots of amps metal to metal. If the relay gets stuck it isn't protecting anybody.
Quote


Yes, I know we're looking for something that doesn't require the musicians to add them into their signal chain, so perhaps a specialized backline AC power GFCI is the best solution. But I can't help but think that opening up the guitar signal cable is a good way to protect the guitarist from a "hot" mic as well as a "hot" chassis guitar amp. More to think about.   
As I already mentioned I will talk to my friend who owns a guitar pedal company to investigate building some protection inside.  Back when you were talking with that guitar maker who was adding fuses into his guitars (??I don't remember fuse value or company). I wonder if he is getting a decent price... I don't trust the quotes I've seen so far (too high).

I also thought about maybe putting a pair of 1/4" guitar jacks in the GFCI outlet strip with a relay for the muso to patch in series between his guitar and pedals or amp, but nobody want to add any extra cable length (capacitance).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 12, 2014, 09:05:36 pm
I can see the guitar forum thread now.  I would use the Sokol box but it colors my sound.

I know what you meen but if you use it with a 12AX7 input it is a very nice color.

No. If you use it at the input of your pedal board with a guitar with a active pickup you only get the slightest warming effect.  I actually like two of them to get the best sound.
Indeed... while not exactly a guitar forum, there was a pretty extensive thread a few years ago in Geekslutz (more of a recording forum) discussing the preferred internal modification to the guitar. A small cap (.03uF or so) was inserted between the exposed metal parts of a guitar and the real ground that is still connected to the pickup and amp. 

So sonically this guitar tone should be unaffected, while hum pickup from proximate humans is well attenuated. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 12, 2014, 09:37:00 pm
I know what you mean but if you use it with a 12AX7 input it is a very nice color.

But I'm pretty you can't run a 12AX7 from a partially depleted 9-volt battery....  :o
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 13, 2014, 12:58:07 am
As long as we are considering relays, why not just open up hot, neutral and ground with a 3 pole relay if 6 + mA current is detected on the EGC?  It would obviously need to be a manual reset-but IMO, if you are going to open a ground you need to open the mains with another set of contacts.

I am thinking the circuitry is already designed-the exact same circuit that detects a 6 mA difference  between the hot and neutral in a GFCI would detect a 6 mA current in a single wire-so if you had a GFCI with a second trip circuit detecting current on the EGC that would shut down the circuit opening all three wires it should provide very thorough personnel protection.

Prototyping one might make for an interesting winter project.  It would stand to reason that using circuits that are already UL listed would help with development costs-but maybe that is not a reasonable process?

As for a cheap inline GFCI, I can buy a quality GFCI receptacle for $11 and have seen GFCI's designed to be hardwired in without a receptacle for $15.  Granted the inline is likely plug and play and listed for such use-but if we are making modifications that listing goes out the window anyway.
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 13, 2014, 03:34:07 am
Wireless mic and guitar pack.  Performer wears rubber soled shoes as a backup.  :-)
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on December 13, 2014, 04:20:02 am
but nobody want to add any extra cable length (capacitance).

Except for Eric Johnson who chooses his leads depending on the effect they have on the sound.  He also claims to be able to tell the difference in sound between bare brass plugs and nickel plated - so he either has great hearing or is a complete wacko!

Wireless mic and guitar pack.  Performer wears rubber soled shoes as a backup.

Or petrol powered guitar amps with generators built in - although mine would have to be steam powered!


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 13, 2014, 06:48:51 am
Or petrol powered guitar amps with generators built in - although mine would have to be steam powered!

Steve, that's brilliant. We've been discussing flame and air powered speakers at http://forums.prosoundweb.com/index.php/topic,152585.0.html (http://forums.prosoundweb.com/index.php/topic,152585.0.html)

I can see a guitar player digging a wall of flame that's his speaker. Now, how do you do tone controls with it?  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve Bradbury on December 13, 2014, 10:33:27 am
The main problem with any separate engineered solution is that it can it be bypassed. If it can, at some point it will. The idea of placing a capacitor in series with the cable shield might work great but at some time in the future it will either go faulty or be misplaced. At that time the guitar player will most likely grab the closest replacement that works. If the safe cable was masking a fault and was the only thing protecting him….. Ouch!

The real solution, in my opinion, is to try and eliminate the dangerous equipment in the first place rather than add patches. Yes there will still be problems, but that is the point of protective earth cables. A fault trips a breaker rather than killing someone. Regular in service testing should also help reduce problems.

Any equipment that is not class2 (double insulated) and doesn’t have an earth should fail an in service test (PAT). Try telling that to a guitarist about his favourite vintage amp. Any method of ensuring safe operation of such an amplifier needs, in my opinion, to be built into the amplifier, or be incorporated in such a way that the amplifier can’t be used without it.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 13, 2014, 10:51:36 am
As long as we are considering relays, why not just open up hot, neutral and ground with a 3 pole relay if 6 + mA current is detected on the EGC?  It would obviously need to be a manual reset-but IMO, if you are going to open a ground you need to open the mains with another set of contacts.
I like it except the 3 pole relay is not a common form factor. I need to study if GFCI opens up both hot and neutral or only hot (probably just hot). I can probably force trip the GFCI when I open the ground.
Quote
I am thinking the circuitry is already designed-the exact same circuit that detects a 6 mA difference  between the hot and neutral in a GFCI would detect a 6 mA current in a single wire-so if you had a GFCI with a second trip circuit detecting current on the EGC that would shut down the circuit opening all three wires it should provide very thorough personnel protection.
I may need to experiment with this, there should be no difference between a 6 mA difference between two leads and 6ma on 1 lead. So that cheap magnetic circuit "could work".

The company that makes the GFCI extension cords has a patent on a leakage detection interruptor that uses voltage in a shield to trip SCRs that disconnect power but I want to do more than turn off the units power.
Quote
Prototyping one might make for an interesting winter project.  It would stand to reason that using circuits that are already UL listed would help with development costs-but maybe that is not a reasonable process?

As for a cheap inline GFCI, I can buy a quality GFCI receptacle for $11 and have seen GFCI's designed to be hardwired in without a receptacle for $15.  Granted the inline is likely plug and play and listed for such use-but if we are making modifications that listing goes out the window anyway.
Yup the company I referred to (Tower manufacturing) makes several different GFCI variants. They have a few related patents and should know the technology, but I want to get my feature set figured out before I approach them.

JR

PS: opening the safety ground is a foreign concept for UL et al. but who can argue with opening all three?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 13, 2014, 10:54:05 am
Except for Eric Johnson who chooses his leads depending on the effect they have on the sound.  He also claims to be able to tell the difference in sound between bare brass plugs and nickel plated - so he either has great hearing or is a complete wacko!
Hearing cable length/capacitance is entirely plausible. Hearing brass vs nickel plated connectors is a little silly.

JR
Quote
Or petrol powered guitar amps with generators built in - although mine would have to be steam powered!


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 13, 2014, 11:06:16 am
The main problem with any separate engineered solution is that it can it be bypassed. If it can, at some point it will. The idea of placing a capacitor in series with the cable shield might work great but at some time in the future it will either go faulty or be misplaced. At that time the guitar player will most likely grab the closest replacement that works. If the safe cable was masking a fault and was the only thing protecting him….. Ouch!
Anything that could save lives is on the table. To be honest this is not as big of a problem as bad air bags or ignition keys that turn themselves off.
Quote
The real solution, in my opinion, is to try and eliminate the dangerous equipment in the first place rather than add patches. Yes there will still be problems, but that is the point of protective earth cables. A fault trips a breaker rather than killing someone. Regular in service testing should also help reduce problems.
Of course but we do not live and operate in that ideal world. I still think guitar amps that are routinely a source of shocks need to fed from a GFCI so they will trip. If the musician ignores the very obvious hazard and bypasses the GFCI they get what they get. The support crew is not supporting anybody by helping the talent do that and putting themselves at financial risk.
Quote
Any equipment that is not class2 (double insulated) and doesn’t have an earth should fail an in service test (PAT). Try telling that to a guitarist about his favourite vintage amp. Any method of ensuring safe operation of such an amplifier needs, in my opinion, to be built into the amplifier, or be incorporated in such a way that the amplifier can’t be used without it.

I still worry about the potential for flaky mains power at either FOH or back line, that could make perfect ground bonded gear a shock hazard between two power drops (it happens). Usually after somebody gets killed, they resolve the safety problem but there were symptom of the problem for far too long that were ignored or dismissed.   

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 14, 2014, 12:02:02 am
JR,

After some thought here is how I would prototype this:

Power comes into "protective device" to a standard gfci receptacle or standalone device.

From that output we go to a " modified gfci"  Modified in this manner- the hot and neutral wires are rerouted  bypassing the sensing CT.  (The  actual how of this obviously depends on the mechanical construction of the GFCI).

The output of this "modified GFCI" goes to the coils of a 3p relay (ice cube relays with 3 poles are not hard to find).  The outputs also go to 2 of the poles on the relay.

The EGC from the source is fed through the sensing CT on the modified GFCI to the third pole on the relay. 

Then using NO contacts on the relay, neutral and hot are carried through. The EGC downstream of the 3rd pole on the relay can bond the "protective device"'s enclosure and downstream gear.

A hot to ground fault or leak will fault the "factory" gfci, dropping power to relay and disconnecting all three wires.

Any fault causing 6+ mA on the EGC will trip the "modified GFCI" and drop out the relay.  This could be a hot fault supplied from another piece of gear, or current resulting from a RPBG supplying current though the "protective device".

So, the device that trips would give an indication as to the type of fault-the sole exception being a fault from the hot to the EGC of the protective device as that will result in a race condition and anybody's guess as to which device will trip first.

I suppose a reasonable level of safety could result from using a 2 pole relay to break the neutral and ground (I am assuming that the neutral is not disconnected with a gfci-but that is an unknown for me as well.).  I do kind of like the fact that if the coil on the relay failed with a 3 pole there would be nothing energized-though even if there were it would be GFCI protected.

I may be missing something, but it seems like this should provide the level of safety you are after?   
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 14, 2014, 01:06:25 am
PS: opening the safety ground is a foreign concept for UL et al. but who can argue with opening all three?

I think the issue is that the chassis ground of Device A needs to be able to trip a breaker when a fault in Device B makes it live.

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 14, 2014, 10:21:33 am
I think the issue is that the chassis ground of Device A needs to be able to trip a breaker when a fault in Device B makes it live.

While I am repeating myself, I have spent decades wrestling with this conundrum. Yes, ground bonding the chassis of single insulated, powered gear is the standard for human safety. That said it is precisely this scenario (a musician finding himself between two different mains power drops) where properly ground bonded chassis can actually be the hazard from mains wiring faults that kills the musician (it has happened). The human mains power shunt will not trip the circuit breaker.

In general I do not embrace floating the chassis in a single insulated design, especially for a vacuum tube amp that has it's own dangerous internal voltages. BUT a GFCI in series with the guitar amp should protect against at least any primary power supply fault. I am not confident that a GFCI on the FOH power would protect against a RPBG.

The only fully protective mod is cap coupling inside the guitar, and guitar makers would be smart to do that (IMO). While we do not have numerous dead musicians driving this, something as cheap as a cap seems reasonable. 

I have not investigated this but it seems a UL approved stinger cap design "should" (?) require double insulated primary wiring to reduce that hazard.
 
JR

Note: they do sell GFCI plugs that can be attached to gear while not as cheaply as I would like. A guitar amp manufacturer could incorporate GFCI less expensively but that is a price competitive market so unlikely to happen.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 14, 2014, 11:30:14 pm
I think the issue is that the chassis ground of Device A needs to be able to trip a breaker when a fault in Device B makes it live.

But this needs to be addressed at the supply side of device B-there are just too many potential paths to ground many of which are not connected through any gear/device/receptacle.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Dawson on December 16, 2014, 03:54:09 pm
As a bit of a sideways swerve, on the topic of protecting consoles with multiple mics into them, how do we factor in the use of a UPS between the Gfci and the console/stage box or similar?    At a first thought I'd consider a UPS like an isolating transformer, but I don't think that's correct for many designs..
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 16, 2014, 04:41:22 pm
As a bit of a sideways swerve, on the topic of protecting consoles with multiple mics into them, how do we factor in the use of a UPS between the Gfci and the console/stage box or similar?    At a first thought I'd consider a UPS like an isolating transformer, but I don't think that's correct for many designs..
I would be apprehensive that a UPS might conceal a ground fault occurring post the UPS. I'd prefer a GFCI outlet  on the UPS.

That said a RPBG may make all of that attempted protection moot, assuming the now hot safety ground passes through the UPS.

Danger Will Robinson...

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 16, 2014, 07:30:32 pm
The ultimate solution might be a ups incorporating a GFCI output, with EGC current monitoring to disable the output.  The problem is going to be getting a UL listing as the cost of doing so is going to be spread out over a limited number of units.  As much as I hate code mandating good practices, forcing the use of a protective device like this may be the only way to drive demand up high enough to justify the cost.

It would help if there were another industry that the technology would make a lot of sense on-RVs Mike?  It would be a short step from an ice cube relay to a 50 o even 100 amp definite purpose contactor that would energize the entire RV upon a fault?

I assume that once a concept design is listed that variants of that design require less exhaustive testing?
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 16, 2014, 07:39:44 pm
I would be apprehensive that a UPS might conceal a ground fault occurring post the UPS. I'd prefer a GFCI outlet  on the UPS.

That said a RPBG may make all of that attempted protection moot, assuming the now hot safety ground passes through the UPS.

Danger Will Robinson...

JR

Yes, the RPBG (Reverse Polarity Bootleg Ground) condition will energize the EGC safety-ground wire and everything with a grounded power cord plugged into it. Since the NEC/UL doesn't allow the ground wire to have a disconnect contact, then it follows that no currently approved voltage monitoring or protection device will disconnect you from a hot ground caused by one. Seems crazy, but that's how it works.

Of course, an RPBG outlet should NEVER happen in the first place, especially with newer wiring (post 1970). However, I've discovered several RPBG outlets in churches just in the last year where a DIY volunteer has upgraded the old 2-banger outlets on stage to grounded ones. So that's now my warning sign. If I'm in an old church and see new outlets on the back wall behind the band, my spider sense starting tingling and I get out my NCVT for quick test even if I'm not using them for my seminars. I also double-check the chassis of my mixing console after plugging it in to make sure it doesn't have a hot-chassis condition.

Just know that any old bar stage with new outlets on the wall behind the band is suspicious as are new grounded outlets in old garages. In short, anyplace with older wiring (especially K&T) that has new "grounded" outlets needs a double-check for RPBG mis-wiring. You also need to know that a 3-light cube tester won't discover an RPBG mis-wiring condition. It will show the outlet as being wired correctly, when the ground and neutral are at 120-volts and the hot is at 0 volts.

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 16, 2014, 07:58:14 pm
It would help if there were another industry that the technology would make a lot of sense on-RVs Mike?  It would be a short step from an ice cube relay to a 50 o even 100 amp definite purpose contactor that would energize the entire RV upon a fault?

I have one of the EMS (Electrical Management System) manufacturers considering a sensor that would at least warn you that an RV hot-skin condition (common RV slang) has occurred, even if they're not allowed to disconnect the RV from the hot-ground wire at this time. However, that's exactly the sort of exception that the NEC might make. And you're correct, that one exception just might make it possible for an EMS type of device to monitor and disconnect the sound gear ground if a hot-chassis condition occurs.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 17, 2014, 12:26:44 pm
As long as we are considering relays, why not just open up hot, neutral and ground with a 3 pole relay if 6 + mA current is detected on the EGC?  It would obviously need to be a manual reset-but IMO, if you are going to open a ground you need to open the mains with another set of contacts.

I am thinking the circuitry is already designed-the exact same circuit that detects a 6 mA difference  between the hot and neutral in a GFCI would detect a 6 mA current in a single wire-so if you had a GFCI with a second trip circuit detecting current on the EGC that would shut down the circuit opening all three wires it should provide very thorough personnel protection.

Prototyping one might make for an interesting winter project.  It would stand to reason that using circuits that are already UL listed would help with development costs-but maybe that is not a reasonable process?

As for a cheap inline GFCI, I can buy a quality GFCI receptacle for $11 and have seen GFCI's designed to be hardwired in without a receptacle for $15.  Granted the inline is likely plug and play and listed for such use-but if we are making modifications that listing goes out the window anyway.

I am liking this approach. Two different current transformers, one differential transformer for the hot and neutral, a second current transformer for just the ground lead. If hot and neutral are mismatched by 6 mA, or if the ground lead carries 6 mA, a 3 pole relay or latching switch opens all three conductors. (UL might insist on breaking the hot-neutral before breaking the EGC which sounds more expensive.)

This is a foreign concept to UL who do not think in terms of opening EGC paths, but in my judgement is the only way to protect a guitar player from both a faulty amp or bad electrical service, his or FOH.

Thanks Stephen, et al.

JR

PS: I am going to try to bounce this idea off a guy with a couple GFCI patents and he may have some ideas about a cost effective approach. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 17, 2014, 12:59:12 pm
The one place NEC and UL do condone disconnecting the ground is with a plug and cord connected device.  If you discovered a RPBG the first thing you should/would do would be to unplug any connected gear.  I would sell this to them as an "automatic unplugger".  Build the device itself in an enclosure to double insulated standards so it does not itself require an EGC.

I also considered they may want to see a "force guided" contact relay.  (I think that is the term that was used.)  So these quite often in safety circuits-the idea being that all the contacts had to make/break together.  It is possible for a contact in a standard ice cube relay to stick while the others operate. (Not common but possible.) 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 17, 2014, 01:07:01 pm
I am liking this approach. Two different current transformers, one differential transformer for the hot and neutral, a second current transformer for just the ground lead. If hot and neutral are mismatched by 6 mA, or if the ground lead carries 6 mA, a 3 pole relay or latching switch opens all three conductors. (UL might insist on breaking the hot-neutral before breaking the EGC which sounds more expensive.) 

JR, I'm pretty sure that a single current transformer with all three wires (H-N-G) running though it would detect any external fault leakage, whether outgoing from the guitar's hot chassis, or incoming from a hot mic. At least that's how I'm drawing it and following the paths inside my head. Easy enough to try with a clamp ammeter and a few "leak" resistors.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 17, 2014, 01:32:25 pm
JR, I'm pretty sure that a single current transformer with all three wires (H-N-G) running though it would detect any external fault leakage, whether outgoing from the guitar's hot chassis, or incoming from a hot mic. At least that's how I'm drawing it and following the paths inside my head. Easy enough to try with a clamp ammeter and a few "leak" resistors.

I thought about that before and yes, it should detect an external fault current very inexpensively but it might interfere with detecting an internal flaky guitar amp leaking hot to it's own EGC since they would still null out(?).

 I think it needs to be two separate current transformers, but I am open for all suggestions. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 17, 2014, 03:19:30 pm
I think it needs to be two separate current transformers, but I am open for all suggestions. 

You could be right. There's a lot of different possible failure modes to consider. And throwing a possible RPBG outlet into the mix complicates things even further. But I'm a firm believer in the logic that if it CAN happen, then it WILL happen.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 17, 2014, 06:12:34 pm
The other concern would be an amp without an egc or missing a ground pin with a fault causing it to have hot chassis being used with another grounded piece of gear also supplied by the "protective device"-if one CT is used a hot-egc fault will not be detected. A separate CT will trip on EGC current regardless of where it comes from.

I have to believe that adding another CT to an existing GFCI design should be a minimal cost,  the 3 pole 20 amp relay is the tough part to get around as far as cost-but I can't figure a good way around that-Solid state might save cost, but I don't trust it for a safety disconnect.

What I am not familiar with is the internal testing modern GFCIs do-what makes them know not to rest if they are defective?  That might throw a monkey wrench in things-I am guessing the UL guys will want to maintain that standard.

 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 17, 2014, 07:07:29 pm
The other concern would be an amp without an egc or missing a ground pin with a fault causing it to have hot chassis being used with another grounded piece of gear also supplied by the "protective device"-if one CT is used a hot-egc fault will not be detected. A separate CT will trip on EGC current regardless of where it comes from.
Lets hope
Quote
I have to believe that adding another CT to an existing GFCI design should be a minimal cost,
I suspect every penny counts in these things.
Quote
the 3 pole 20 amp relay is the tough part to get around as far as cost-but I can't figure a good way around that-Solid state might save cost, but I don't trust it for a safety disconnect.
I'm with you.. I don't trust solid state for complete isolation.

I've looked at some patents from a guy with a few GFCI designs and he used a latching relay with two contacts in one... it seems a third contact is not huge.

I tried to explain the issues as I understand them to him, I expect him to know the cheapest way to do it. Problem still is that I don't see a market large enough to justify too much cost/effort.


Quote
What I am not familiar with is the internal testing modern GFCIs do-what makes them know not to rest if they are defective?  That might throw a monkey wrench in things-I am guessing the UL guys will want to maintain that standard.

Another tidbit, I suspect the UL guys will be reluctant to give up ground bonding, but if they do they will probably want to delay releasing the ground bond until after the hot and neutral is already open.

Lets hope I get a serious answer... it would be nice to come up with an effective solution for this.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 17, 2014, 08:13:52 pm
Another tidbit, I suspect the UL guys will be reluctant to give up ground bonding, but if they do they will probably want to delay releasing the ground bond until after the hot and neutral is already open.

I hope that UL will allow an exception for a EGC contact in the AC power, but if that's not possible then remember that a double-pole/mag-set reed relay in the guitar's signal cable would accomplish the same disconnect for the guitarist. However, it would NOT eliminate the shock hazard from someone touching the hot chassis of the guitar amp and a grounded object. So you would still need a standard GFCI powering the amp for that sort of fault protection.
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on December 17, 2014, 08:47:58 pm
....., but if that's not possible then remember that a double-pole/mag-set reed relay in the guitar's signal cable would accomplish the same disconnect for the guitarist. However, it would NOT eliminate the shock hazard from someone touching the hot chassis of the guitar amp ....
which could lead back to my idea of a D.I. based solution. Even though I use a mic for the guitar, I always have a free strip or three somewhere that could supply phantom power to a couple of "Guitar No Shock" boxes.
I always use volt-alert, but in the heat and confusion, shit happens that I may not catch. I haven't killed anyone yet, and have no intention of ever letting it happen.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 18, 2014, 09:57:32 am
I have a friend who makes guitar pedals (amptweaker.com) and I still plan to ask him what he thinks. He's an actual design engineer and since his pedals have battery power he could probably add a latching relay protection inside a pedal, while he may also have a feel for how much (little) guitar players are willing to pay for the extra human safety.

I'm leaning toward a small relay and perhaps < 6 mA threshold in guitar lead. 

I need to ask him today, while hopefully he is busy with christmas sales.

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 18, 2014, 10:00:19 am
which could lead back to my idea of a D.I. based solution. Even though I use a mic for the guitar, I always have a free strip or three somewhere that could supply phantom power to a couple of "Guitar No Shock" boxes.
I always use volt-alert, but in the heat and confusion, shit happens that I may not catch. I haven't killed anyone yet, and have no intention of ever letting it happen.
Just to run out this hypothetical if you have a console grounded mic pointed at the guitar cabinet and the player with guitar in hand touches that mic for any reason he will be putting himself between two EGC systems and exposed to potential shock hazard.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 18, 2014, 10:51:44 am
I have a friend who makes guitar pedals (amptweaker.com) and I still plan to ask him what he thinks. He's an actual design engineer and since his pedals have battery power he could probably add a latching relay protection inside a pedal, while he may also have a feel for how much (little) guitar players are willing to pay for the extra human safety.

I'm leaning toward a small relay and perhaps < 6 mA threshold in guitar lead. 

I need to ask him today, while hopefully he is busy with christmas sales.

JR

Exactly.... but my napkin design suggests that a current transformer just might have enough output current to open up a latching reed relay. And a permanent magnet on a push button could "reset" the latching relay if it trips. If that's indeed the case, then this device could fit in a plastic in-line box that connects between the guitar cable and the amplifier. If (and this is a big IF) there's enough current flow from the current sensing transformer to open up the latching relay without amplification, then there are no batteries required. I'm going to see if I can get a few current transformers and latching reed relays to play with.

However, if this was something that could be built and sold for $50 at a profit, would that be too much money? Or is $30 a more acceptable price? Just remember that for this to happen there has to be a certain amount of profit in building and selling it. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 18, 2014, 11:40:25 am
Exactly.... but my napkin design suggests that a current transformer just might have enough output current to open up a latching reed relay. And a permanent magnet on a push button could "reset" the latching relay if it trips. If that's indeed the case, then this device could fit in a plastic in-line box that connects between the guitar cable and the amplifier. If (and this is a big IF) there's enough current flow from the current sensing transformer to open up the latching relay without amplification, then there are no batteries required. I'm going to see if I can get a few current transformers and latching reed relays to play with.

However, if this was something that could be built and sold for $50 at a profit, would that be too much money? Or is $30 a more acceptable price? Just remember that for this to happen there has to be a certain amount of profit in building and selling it.

What is the impedance of a latching relay winding? Maybe put the relay coil winding right in series with the ground path?

Bzzzt..wrong. I just did a quick search and the lowest current relay I could find at just over 1 mA also required 24V. Elsewhere on the spec sheet they say 30 mW of power to switch the relay and that relay coil is 20k ohm. Relays come in all flavors of coil impedance and working voltage but the bottom line is they need 50-100mW to switch a small signal relay, so a relay with .5V coil requires 140 mA. A big relay would require more power.

=====
My pedal making friend mentioned that some in the guitar industry use transformer isolation for signals, I questioned how well that would work on lead guitar and he didn't answer back.   I expect you use an output transformer in a floor pedal to break the ground path without compromising tone too much. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on December 18, 2014, 11:42:27 am
Just to run out this hypothetical if you have a console grounded mic pointed at the guitar cabinet and the player with guitar in hand touches that mic for any reason he will be putting himself between two EGC systems and exposed to potential shock hazard.

JR
My thinking is that the DI senses >6ma current in the guitar lead, and kills both conductors of that lead.
Exactly what does a humbucker put out, current wise ?? Bob ??
With phantom, or an on-board 9V, I am sure there is plenty of juice available to trip off a reed relay. No power, and the guitar lead is disconnected.
Not all that different from your pedal idea, just move the responsibility to me, not the guitarist. After all, aren't all us sound guys just glorified control freaks ?  :D
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 18, 2014, 01:08:01 pm

However, if this was something that could be built and sold for $50 at a profit, would that be too much money? Or is $30 a more acceptable price? Just remember that for this to happen there has to be a certain amount of profit in building and selling it.


Unfortunately safety devices don't command the demand that they should IMO.  I find more resistance to safety spending with individuals-with businesses concerned about liability/image etc, usually cost is not a factor. They certainly won't ask the paramedics how much it will cost for an attempt to resuscitate them after they get a good jolt, but "it'll never happen to me" .

So I guess the potential sale price depends on how effective Mike is at educating the masses.  :)
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 18, 2014, 01:44:48 pm
What is the impedance of a latching relay winding? Maybe put the relay coil winding right in series with the ground path?

Bzzzt..wrong. I just did a quick search and the lowest current relay I could find at just over 1 mA also required 24V. Elsewhere on the spec sheet they say 30 mW of power to switch the relay and that relay coil is 20k ohm. Relays come in all flavors of coil impedance and working voltage but the bottom line is they need 50-100mW to switch a small signal relay, so a relay with .5V coil requires 140 mA. A big relay would require more power.

=====
My pedal making friend mentioned that some in the guitar industry use transformer isolation for signals, I questioned how well that would work on lead guitar and he didn't answer back.   I expect you use an output transformer in a floor pedal to break the ground path without compromising tone too much. 

JR

Drats.... But this would certainly work with an op-amp comparator circuit and a 9-volt battery. However, a failed battery would allow the shock to get through. You could also use phantom for the power, but that's one more connection that can go wrong. More to consider.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 18, 2014, 01:51:09 pm
Drats.... But this would certainly work with an op-amp comparator circuit and a 9-volt battery. However, a failed battery would allow the shock to get through. You could also use phantom for the power, but that's one more connection that can go wrong. More to consider.

A non-latching relay that opens when power isn't present would be safe, but would draw circa 10mA from 9V battery.

This gets me back to mains power. Since an outlet strip has power... I come full circle back to my smart power strip.

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 18, 2014, 02:00:26 pm
Drats.... But this would certainly work with an op-amp comparator circuit and a 9-volt battery. However, a failed battery would allow the shock to get through. You could also use phantom for the power, but that's one more connection that can go wrong. More to consider.

If you want to play along with the design process, here's how these latching reed relays work. http://www.meder.com/fileadmin/meder/pdf/en/Technical_Documents/Application_Notes/ReedSwitchNoOrLowPowerSolution-0209.pdf (http://www.meder.com/fileadmin/meder/pdf/en/Technical_Documents/Application_Notes/ReedSwitchNoOrLowPowerSolution-0209.pdf)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 19, 2014, 03:38:19 pm
OK more questions for my feature list. If I design my hypothetical "smart" outlet strip, it could combine a conventional GFCI function with a separate relay contact to break the ground connection if it senses current there. ASSuming I could make this smart enough to detect several faults or issues how do we want it to respond. 

On order of increasing severity.

#1 Hot and neutral reversed but good** ground path connection.

Response A- ignore and connect power
   B- indicate the reversed connection but connect power
   C- actively correct the reversed connection before connecting power (more expensive)
   D- do not connect power until reversed connection repaired.

   *** fairly simple to detect floating ground from valid ground, but bootleg ground to neutral will also indicate good unless more testing is added.
   response if ground is floating
      A- apply power to hot and neutral but indicate ground is open
      B- do not power up
      c- internally boot leg ground to neutral and indicate.  (more expensive)

detect for bootleg ground to neutral (more expensive_
   A- if bootleg ground detected light an indicator but apply power.
   B- if bootleg detected do not power up.

detect for RPBG
   A- If RPBG detected light an indicator but still power up (note ground current sense will still shut down the power if any ground current is detected.
   B- automatically reconfigure the correct polarity and bootleg the ground to the actual neutral (with indication that outlet is dangerous)
   C- do not power up.

As you can see many options and I consider some of them too complex and expensive. Alternately manual switches could be used to manually correct reversed polarity and to make bootleg ground connections if needed.  Smart detection could still prevent the main power relay from connecting with faulty power or ground settings.  I could imagine not turning on until a floating ground was manually bootlegged to neutral (IMO safer than floating).

What cha think?

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 19, 2014, 11:36:02 pm
Existing GFCIs are designed not to work if hot/neutral are reversed-but they might have to be in the tripped condition for this to work (obviously no one expects an electrician to remove a working GFCI and reverse the wires).

A lot would depend on the reliability of your detection methods-specifically IDing the hot/neutral with a non existent ground.  NCVD are not 100% reliable-and if you bootleg to the wrong wire you create a RPBG-how often is that failure acceptable?  IMO, a floating ground-on a GFCI circuit-is not a big issue for safety, it might be for noise in sound gear.

In a safety class a few years ago, a trainer explained a pet peeve of his-"Wet Floor" signs.  He pointed out you were aware of a hazard-but did nothing to correct it-ie dry the floor, etc.  I may be pessimistic, but I would lean towards letting it feed through power if hot/neutral were correct and ground was either floating or correct any other conditions cause a lock out.
A visual indication of a good ground could be helpful for gear that needs a good ground to run properly.
 
If you have reverse polarity or RPBG, how confident are you that the circuit is otherwise safe to use?

But then I got zapped last spring by an energized green ground wire, so I my tolerance for incorrect wiring practices is at a low point right now! 
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on December 20, 2014, 01:24:20 am
Existing GFCIs are designed not to work if hot/neutral are reversed-but they might have to be in the tripped condition for this to work (obviously no one expects an electrician to remove a working GFCI and reverse the wires).

A lot would depend on the reliability of your detection methods-specifically IDing the hot/neutral with a non existent ground.  NCVD are not 100% reliable-and if you bootleg to the wrong wire you create a RPBG-how often is that failure acceptable?  IMO, a floating ground-on a GFCI circuit-is not a big issue for safety, it might be for noise in sound gear.

In a safety class a few years ago, a trainer explained a pet peeve of his-"Wet Floor" signs.  He pointed out you were aware of a hazard-but did nothing to correct it-ie dry the floor, etc.  I may be pessimistic, but I would lean towards letting it feed through power if hot/neutral were correct and ground was either floating or correct any other conditions cause a lock out.
A visual indication of a good ground could be helpful for gear that needs a good ground to run properly.
 
If you have reverse polarity or RPBG, how confident are you that the circuit is otherwise safe to use?

But then I got zapped last spring by an energized green ground wire, so I my tolerance for incorrect wiring practices is at a low point right now!

I may be off base but let me toss something out.  Rather than analog devices have you consider a small uP?  Certainly if a small RF tracer signal ,from an amplified TTL output switched on and off very fast, was induced on the hot leg the corresponding return signal would radically differ with a device that produced a hot chassis.  By producing a couple 100 samples of gear in distress the samples could be plotted and a distress signature identified.

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 20, 2014, 08:40:38 am
Existing GFCIs are designed not to work if hot/neutral are reversed-but they might have to be in the tripped condition for this to work (obviously no one expects an electrician to remove a working GFCI and reverse the wires).

I'm not sure that's true. If the GFCI doesn't require a ground wire, then just how does it tell the difference between correctly wired and swapped H-N connections? The big question should be does the GFCI open up both the Neutral and Hot lines? I believe they do, at least in the ones that I've seen. But perhaps there are versions that only open up the "Hot" side. If that's the case, the a tripping GFCI would not isolate you from a ground fault shock.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 20, 2014, 09:12:03 am
Existing GFCIs are designed not to work if hot/neutral are reversed-but they might have to be in the tripped condition for this to work (obviously no one expects an electrician to remove a working GFCI and reverse the wires).
I don't quite follow...
Quote
A lot would depend on the reliability of your detection methods-specifically IDing the hot/neutral with a non existent ground.  NCVD are not 100% reliable-and if you bootleg to the wrong wire you create a RPBG-how often is that failure acceptable?  IMO, a floating ground-on a GFCI circuit-is not a big issue for safety, it might be for noise in sound gear.

I have scratched up some simple circuits using passive components that I should be able to determine the obvious Hot or neutral, and neutral or floating. I am not sure how to reliably determine neutral from ground and may not bother.
Quote

In a safety class a few years ago, a trainer explained a pet peeve of his-"Wet Floor" signs.  He pointed out you were aware of a hazard-but did nothing to correct it-ie dry the floor, etc.  I may be pessimistic, but I would lean towards letting it feed through power if hot/neutral were correct and ground was either floating or correct any other conditions cause a lock out.
A visual indication of a good ground could be helpful for gear that needs a good ground to run properly.
 
your vote is registered.
Quote
If you have reverse polarity or RPBG, how confident are you that the circuit is otherwise safe to use?
I would prefer to not operate that way and my whole premise is that I can sense current in the ground and release if it senses more than a few mA.  I could also add another relay that fixes the RPBG so the outlets in the power strip are good, but my gut feeling is that RPBG should light a blinking strobe light and a klaxon alarm until it is fixed. Maybe invent a plug that melts blocking the outlet and prevents other people from using it.
Quote
But then I got zapped last spring by an energized green ground wire, so I my tolerance for incorrect wiring practices is at a low point right now!
Yup many more people get shocked than actually killed but preventing shocks would be nice too.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 20, 2014, 09:23:14 am
I may be off base but let me toss something out.  Rather than analog devices have you consider a small uP?  Certainly if a small RF tracer signal ,from an amplified TTL output switched on and off very fast, was induced on the hot leg the corresponding return signal would radically differ with a device that produced a hot chassis.  By producing a couple 100 samples of gear in distress the samples could be plotted and a distress signature identified.

I have written many thousands of lines of micro code so I could easily program a micro, I am not as certain that I could reliably learn anything from injecting a high edge rate signal onto a hot power line. If anything I would probably learn more about if the product has a line cord power filter like used for switching PS units with switching noise. Tell me more if you have a specific idea how this should work.

In my judgment the decision tree for a smart power strip is simple enough that a processor is probably not needed. Cheap modern micros have 12 bit A/D on board so I could use that for my precision current sense, and to maybe determine if ground is bootlegged.  At this point I worry it is already getting too expensive so would like to keep it simple.

Injecting some HF into the ground could be useful to measure ground inductance but probably TMI for an outlet strip. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 20, 2014, 01:19:12 pm
New (at least quality name brand-I won't use bargain basement junk for my installs) are shipped "tripped"-they must be reset after power is applied.  They will not reset if H-N are wrong-of course on a 2 wire circuit they can not test for polarity.  I have not tried swapping the H-N after power is applied-and the test may not catch that condition since teh primary purpose is to make sue the install is correct.  A "smart" power strip would effectively be "installed" every time it is plugged in-so the H-N test or reset would need to be performed each time to ensure safety.

Neutral-ground distinction would be tough/impossible.  If I install a correctly wired dedicated receptacle 50 feet from a panel you will have a 50 ft #12 chunk of copper for a neutral and another for the ground-the only difference being the color of insulation.  Determining a bootleg neutral should in theory be possible-for a minimum distance from the panel the distinction being 1" of wire vs X number of feet. In most real world cases the distinction should be significant, but you would have to determine a threshhold.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 20, 2014, 01:41:54 pm
I am not expert about GFCI but I think I have seen some literature where the differential current transformer is grounded somehow. If there is no ground connected it will probably still work as expected but if the hot-neutral is reversed perhaps not.

I am leaning toward adding two switches to the front end of my smart power strip. One a manual DPDT allows the user to swap hot and neutral if they indicate wrong. The second switch a SPST allows the operator to bootleg the ground to neutral if that ground indicates open.

Only after the smart circuitry determines that hot and neutral are connected properly, "and" a ground is present, then it actuates a relay to connect the power strip to the outlets. A standard GFCI outlet is used in the strip.

Further another sensor detects current flowing in the ground lead. If this ground current exceeds X mA the power relay opens up ALL THREE LINES..... I could sense after the GFCI also but that might require a turn on delay to reset the GFCI.

I could make the polarity and bootleg switching automatic with extra relays but IMO that is too much expense, the operator cannot get the relay to connect power without getting everything set right first so no risk of making that manual. If they try to change it while it's already working it will just shut off. 

Now the minor details of figuring out how to do all this but so far nothing looks like it will break the bank or amount to rocket science.

JR

PS: I ASSume a bootleg ground is only dangerous in the reverse polarity case, or if a neutral opens up dumping current into ground. My detection circuitry should protect against both of those scenarios. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 20, 2014, 02:07:14 pm
PS: I ASSume a bootleg ground is only dangerous in the reverse polarity case, or if a neutral opens up dumping current into ground. My detection circuitry should protect against both of those scenarios.

Because an open neutral on a bootleg ground will back-feed the hot voltage/current back into the chassis ground via the resistance of the device, code will NEVER allow a bootleg ground of any kind. While I personally feel that a bootleg ground on an outlet that has proper polarity isn't that dangerous, the NEC/UL feels that it is and won't allow it. But if your smart box can detect and disconnect that condition, perhaps they'll allow an exception.
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 20, 2014, 02:57:56 pm
If we are trying for backline safety:

() Backline must meet current electrical standards.
() Backline must be fitted with a GFCI/RCD.  Or at least powered from one.
() Backline must pass an annual/biannual/whatever test.
   plus
() Legal and financial penalties for noncompliance.

Serious financial penalties for venues without correct electrical installations too.  Got a RPBG? That'll cost you $10k and your venue is closed until it's fixed.   Taking this seriously now?  Still just want the barman to do your electrical works before the morning drunks arrive?

Dangerous stuff is only dangerous because we allow it to continue to be used in the name of art or expedience.  In any other industry gear that was unsafe would be scrapped or refurbished.

The level of safety society accepts is the level of safety you get.
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 20, 2014, 03:12:05 pm
What I am trying to say is that this isn't a technology problem.  It is a bands-and-venues-willing-to-be-unsafe problem.

There is nothing electrically unique about the live sound environment, except that the quest for killer tone is being allowed to trump safety.

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 20, 2014, 04:45:51 pm
What I am trying to say is that this isn't a technology problem.  It is a bands-and-venues-willing-to-be-unsafe problem.

There is nothing electrically unique about the live sound environment, except that the quest for killer tone is being allowed to trump safety.

In fact my whole premise is that musical performance spaces are a unique case because musicians routinely find themselves touching two different power drop EGCs (back line EGC via a guitar and FOH EGC via a mic). The sundry dedicated protection devices do not specifically anticipate a hot external EGC. Of course if every outlet and every piece of equipment was wired and performing properly there never would be a hot EGC or any dead musicians.

I am doing this mainly as a mental exercise and I may build a proof of concept just to prove to myself it can be done, but I will not attempt to arm wrestle UL to take my tens of thousands of dollars so I can tool up and sell a tiny handful of these. That would be stupid, and I try not to be stupid.

Less stupid might be to wire a stinger cap into a GFCI power strip to provide a little extra human safety.

 JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 20, 2014, 05:41:39 pm
The main reason I lean towards a lockout condition if the receptacle is not acceptable is that management tends have tunnel vision-if it works great of not fix it-but if it works with a work around it still works so ho cares?  IN an industrial setting I learned that a temporary work around often became permanent because who wants to interuupt production or spend money to fix something that is not broken?  If the only way to get power for the band is to run a drop cord across the managers desk and unplug his Kuerig machine so you have a good receptacle to use he might decide to fix it.

I realize that making it painful for management by not doing a work around is more doable as an employee vs as a guest sound provider (they might just decide to hire the guy down the street that doesn't care about safety), but that is why I don't care for work arounds.

Of course the other side of that coin is that allowing the operator to properly configure the wiring would encourage leaving the safety device in the circuit rather than just bypassing in a pinch-and I have always felt making safety convenient was a good thing..
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 20, 2014, 06:32:14 pm
The main reason I lean towards a lockout condition if the receptacle is not acceptable is that management tends have tunnel vision-if it works great of not fix it-but if it works with a work around it still works so ho cares?  IN an industrial setting I learned that a temporary work around often became permanent because who wants to interuupt production or spend money to fix something that is not broken?  If the only way to get power for the band is to run a drop cord across the managers desk and unplug his Kuerig machine so you have a good receptacle to use he might decide to fix it.

I realize that making it painful for management by not doing a work around is more doable as an employee vs as a guest sound provider (they might just decide to hire the guy down the street that doesn't care about safety), but that is why I don't care for work arounds.

Of course the other side of that coin is that allowing the operator to properly configure the wiring would encourage leaving the safety device in the circuit rather than just bypassing in a pinch-and I have always felt making safety convenient was a good thing..
I am thinking of something for the musician to carry with him to protect himself from bad venues, not as a semi-permant fix for a venue. Hopefully any outlets he identified as dangerous will get taped over or identified as bad after the gig. The show usually goes on anyhow, just trying to make the musician's personal space a little safer. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 20, 2014, 07:04:26 pm
It is an excellent exercise; an extra level of protection or a deeper understanding of the mechanisms of failure are very good things.

Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on December 20, 2014, 10:03:22 pm
I have been thinking about the question of how injecting a pulse train would detect.  there would need to be a pickup on the ground neutral.  Each fault would have a unique signature much like a radar.  the fault conditions would cause a radical change pattern.    A type of Monte Carlo analysis cpuld be employed to collect a large library of these returns.  Once the fault patterns are qualified you have a single ended non loading detector
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on December 21, 2014, 02:22:47 am
I am thinking of something for the musician to carry with him to protect himself from bad venues, not as a semi-permant fix for a venue.

I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.

Could such a device be built in such a way that it would not sonically color the signal?

Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.

By not being placed in the electrical power path, it would be easier to gain regulatory approval.
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on December 21, 2014, 02:51:00 am
I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.

Could such a device be built in such a way that it would not sonically color the signal?

Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.

By not being placed in the electrical power path, it would be easier to gain regulatory approval.

This was also the theory of my digital scheme.  As it would measure current along with the waveform function on the pickup coil.  All of that data would form the sampled fingerprint.  Easier tuning in the digital domain that with analog components that are also subject to tolerance drift.

If the thing is too sensitive it will become a projectile at FOH.  Digital would allow much more granular false fault rejection processing.

Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 21, 2014, 04:36:14 am
People interact with systems powered from multiple sources and feeds all the time.  We aren't scared of picking up a telephone while using a computer or a kitchen appliance.  Existing electrical safety rules can work if they are followed.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 21, 2014, 09:52:02 am
I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

Like a GFCI, the signal line (positive, shield, and if equipped negative) would pass through a current transformer. Under normal conditions all current flowing through should cancel to zero. But in the event of a ground fault, there would be a imbalaced and therefore nonzero current. If the current exceeds a predetermined value, say 6 mA, the interrupter would open all the signal lines including ground/shield.
Sounds like that should work,,, an external fault current would definitely imbalance the current transformer.
Quote
Could such a device be built in such a way that it would not sonically color the signal?
That I do not know? Guitar pick-ups (especially lead guitar) are relatively high impedance (tens of K ohm) so they would definitely need their own current transformer.
Quote
Such a device could be placed either in the path between the guitar and the amplifier, or between the microphone and the console.
I still lean toward dealing with this at the guitar end because there are multiple dragons to slay (bad stinger caps too).
Quote
By not being placed in the electrical power path, it would be easier to gain regulatory approval.

I have already talked with a friend who makes guitar pedals and there are other options for that signal path. He mentioned to me that some people have used input transformers for guitar amps (I never heard of that and worry about response). While I would not advocate adding input transformers in a guitar path, it seems to me an output transformer in a guitar pedal would be dealing with lower drive impedance and could float that ground path (ASSuming the guitar pedal is battery powered or using an ungrounded wall wart.)

Sensing for current in the single ground lead is a somewhat simpler task than detecting small current leakage from a pair of higher current conductors. 

That said interfering with the guitar signal path could offend the tone snobs and be an added expense most musicians don't feel necessary.  Protecting against legacy guitar amps seems easier to sell to a perhaps wealthier cliental.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 21, 2014, 11:35:47 am
I may have missed it, but the one thing I don't recall seeing in this discussion is a fault current interrupter placed in the signal line.

This is exactly what I've been talking about earlier on this thread, using a pair of magnetic latching reed relays driven by a current transformer. These reed relays would be placed in the guitar signal path and open both the shield and signal lines if more than 6 mA of current went through the current transformer. Because it's a relay contact there should be no signal coloration issues. JR and I have been discussing if there's enough power from the current transformer to trip the latched relay open without a battery for power. JR says no, but I say maybe. More to study to see which one of us is correct. The beauty of opening up the guitar-to-amp signal line is that NEC wouldn't be in the middle of this, and I don't think that UL approval would be required either.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 27, 2014, 05:50:51 pm
OK, first Merry Christmas to everybody...  I think I nailed it. I was thinking too hard looking for a complicated solution using relays and gadgets.... KISS.

The problem I am trying to protect against is a live energized ground, either in the guitar amp or the console power drop. Pulling a very old trick out of my kit bag, separate grounds can be bonded together using diodes. This way as long as the ground voltages are pretty close to each other, the diodes don't conduct and the two grounds appear isolated. BUT, if there is enough voltage difference between the grounds the diode(s) will conduct and presto, no dangerous ground potential.

So my new proposal is a small stage box with two XLR jacks one male and one female with 1,2,3 normalled between them. two 1/4" plugs wired tip to tip and sleeve to sleeve. The jack grounds are isolated from the stage box but connected to each other through back to back diodes (in fact I would use two diode bridges in series for 4x diode drops, or more than 2V before conduction).  An LED could be wired in parallel with the diodes so there would be some LED light should there be a hot ground, but only until a panel circuit breaker or GFCI trips.

In use the musician plugs in his mic and guitar using the mult- through jacks on the box, but these hard wired jacks will not affect his audio path, beyond an extra metal to metal jack contact. The grounds will remain happily floating unless there is more than 2V between the two safety grounds.  If one or the other ground is energized the diode shunt will conduct and take out the fuse, or breaker. or GFCI.

Back in the '80s I did some research and determined that diodes usually fail as a short circuit from over current, so all I need is diodes with enough thermal mass to not vaporize before the mains circuit breakers trip. Diode bridges, like used in power supplies work like a charm. 2 bridges will provide +/- 4 diodes drops so ground noise < 2V will be ignored. (If needed for horrible grounds more diodes could be used in series and this will still protect the meat puppets).

What cha think???  I like it...  No moving parts, and diodes are about the least active of all "active" devices...

JR 

PS: This should also protect against a rouge ungrounded guitar amp bonding it's chassis to the console ground. 

Title: Re: brain storm an optimal human safety system for back line
Post by: Rick Earl on December 27, 2014, 06:17:50 pm


In use the musician plugs in his mic and guitar using the mult- through jacks on the box, but these hard wired jacks will not affect his audio path, beyond an extra metal to metal jack contact. The grounds will remain happily floating unless there is more than 2V between the two safety grounds.  If one or the other ground is energized the diode shunt will conduct and take out the fuse, or breaker. or GFCI.


What cha think???  I like it...  No moving parts, and diodes are about the least active of all "active" devices...

JR 


Would all mics in the system need to be plugged into something like this?  I'm thinking of the sweaty guitar player leaning up against the sweaty singer with a hard wired mic in  hand,  or the bass  player, who may or may not have one.  I deal with a lot of young musicians with a lot of energy and into vintage gear.  I work real hard with them to pay attention to their gear and the venue, but there are still some scary places out there.

Thanks for working on this, it is beyond some of my skill set, but I've been following this thread to help me keep others safe.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 27, 2014, 06:28:00 pm
Would all mics in the system need to be plugged into something like this?  I'm thinking of the sweaty guitar player leaning up against the sweaty singer with a hard wired mic in  hand,  or the bass  player, who may or may not have one.  I deal with a lot of young musicians with a lot of energy and into vintage gear.  I work real hard with them to pay attention to their gear and the venue, but there are still some scary places out there.

Thanks for working on this, it is beyond some of my skill set, but I've been following this thread to help me keep others safe.

No just one mic per stage/back line depending on what the fault is. If the console power drop is hot, that will trip when grounded. If the guitar amp or back line power drop is hot that too should take out the circuit. Of course to protect against individual old legacy killer guitar amps each amp needs to be diode bonded. However a stage box with two or three sets of 1/4" plugs could protect multiple guitar amps while we might need separate diode bridges so each guitar amp is floating for the first 2V relative to the other guitar amp ground.

BTW if your mic or guitar cable melts that is also an indication of a fault.  8) 8) But a mic/guitar cable should hang long enough to trip a breaker or GFCI.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 27, 2014, 06:36:28 pm
Why do the grounds need to be isolated?  In a correctly wired system, they will be bonded together at some point anyway?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 27, 2014, 08:10:33 pm
Why do the grounds need to be isolated?  In a correctly wired system, they will be bonded together at some point anyway?
In theory they could be hard connected but guitar amps are high gain and single ended so likely to hum if the grounds are corrupted... the mic input ground is common mode to the 2 differential mic inputs so should be less likely to pick up noise, but also has a lot of gain so isolated is better IMO.

I believe floating the two grounds with 4 diodes between them is probably a good idea because sundry grounds from different power drops could easily have measurable voltage between them.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 27, 2014, 09:27:00 pm
Why do the grounds need to be isolated?  In a correctly wired system, they will be bonded together at some point anyway?

Most non-isolated grounds will measure anywhere from 0.1 volts up to 2 volts difference between different outlets on opposite sides of a room, or coming from different panels. And this ground voltage differential can change when the loads shift in a building, such as lighting and heaters. Heck, I've even heard refrigerator compressors and big coffee urns modulate ground loop hum when they kick in. If you want to see/hear something crazy, then think about what can happen with standard bootleg grounds or swapped ground/neutral lines. Those conditions will allow the ground voltage differentials to jump up and down by 5 volts or more, depending on load.

The real challenge is that there's a lot of installed power distro that was never grounded properly in the first place, and this shock prevention system needs to account for all sorts of wiring errors.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 27, 2014, 10:23:47 pm
Most non-isolated grounds will measure anywhere from 0.1 volts up to 2 volts difference between different outlets on opposite sides of a room, or coming from different panels. And this ground voltage differential can change when the loads shift in a building, such as lighting and heaters. Heck, I've even heard refrigerator compressors and big coffee urns modulate ground loop hum when they kick in. If you want to see/hear something crazy, then think about what can happen with standard bootleg grounds or swapped ground/neutral lines. Those conditions will allow the ground voltage differentials to jump up and down by 5 volts or more, depending on load.

The real challenge is that there's a lot of installed power distro that was never grounded properly in the first place, and this shock prevention system needs to account for all sorts of wiring errors.

I was pulling the 4 diode drops (roughly 2.4V peak) out of thin air... do you think I need to go to 3x or 4x bridges (4.8V) to be safe? I don't want to conduct current between safety grounds unless there is a hazardous fault, to keep the audio clean.

For human safety 5V is nothing, and as soon as the diodes heat up and melt they fail as dead shorts anyhow...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 28, 2014, 03:52:16 am
The real challenge is that there's a lot of installed power distro that was never grounded properly in the first place, and this shock prevention system needs to account for all sorts of wiring errors.

How does this new system differ from the current wiring rules which need to account for all sorts of wiring errors?

Is it a device we are looking for, or just a practice?  Ie, do all racks get tied together with 4AWG earthing cables before any power is applied?

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 28, 2014, 11:20:02 am
How does this new system differ from the current wiring rules which need to account for all sorts of wiring errors?

Is it a device we are looking for, or just a practice?  Ie, do all racks get tied together with 4AWG earthing cables before any power is applied?

If everything was wired properly and working properly there would be no need for UL or safety rules.

I am trying to protect against multiple hazards.

#1 guitar amps going rouge either from bad stinger cap or other fault with ungrounded chassis.
#2 reverse bootleg mis-wired outlets (at FOH or Back line).
#3 open neutral at FOH or Backline

My shunt between the two safety grounds is not intended to be a fix, but to cause the offending device to take out it's power breaker or GFCI. Hopefully the people involved will consider this as more than a nuisance trip and a real life safety hazard.

I was thinking instead of a LED putting an audible alarm inside the safety shunt to make an annoying sound when fault currents are flowing between safety grounds.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 28, 2014, 03:11:33 pm
Keep in mind that tripping the circuit breaker will require significantly more than 20 amps to do so quickly-most breakers are inverse time delay.  The circuit resistance (an unknown) plus diodes will limit the current to some degree-the greater the limiting the longer it will take to trip the breaker-and some brands of breakers are notorious for taking extended time to trip.

While dual current sensors plus a relays IS more complex, it is less dependent on external factors, IMO.

Mike is right-getting people to view any shock as unacceptable is the key-then they will look for a solution be it a NCVT or whatever.  The next hurdle will be to get them to view an occasional GFCI trip as less of a nuisance than an occasional shock.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 28, 2014, 05:09:01 pm
Keep in mind that tripping the circuit breaker will require significantly more than 20 amps to do so quickly-most breakers are inverse time delay.  The circuit resistance (an unknown) plus diodes will limit the current to some degree-the greater the limiting the longer it will take to trip the breaker-and some brands of breakers are notorious for taking extended time to trip.
I know... the ground bonding test used by UL was around 50A for maybe ten seconds, something like that it was a couple decades ago.

I suspect the combination of mic cord ground resistance and guitar cable resistance could be an ohm or two, but that should still trip a breaker. If it doesn't we have more problems. I would not be surprised if we also see the cords get so hot they melt insulation and deform.
Quote

While dual current sensors plus a relays IS more complex, it is less dependent on external factors, IMO.
Perhaps we can approach this on multiple tracks. For cost is no object,  I would drop in an isolated power supply ($10-20), circuitry to sense current ($15-20), and open not only a relay for the signal and a relay for all three power circuits (another $10?). then this needs to get built into a slick package, for sale to all three or four potential customers.   

The low cost shunt seems more affordable by a larger number of musicians.

Quote

Mike is right-getting people to view any shock as unacceptable is the key-then they will look for a solution be it a NCVT or whatever.  The next hurdle will be to get them to view an occasional GFCI trip as less of a nuisance than an occasional shock.

I have found in life that educating and convincing people to do what they should is a lot harder than providing solutions that do not require them to learn new stuff, or change their former behavior. 

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 28, 2014, 09:07:05 pm
  
The low cost shunt seems more affordable by a larger number of musicians.


It is not surprising that a more robust, comprehensive solution costs more than a solution that primarily protects against one failure mode-but the value of each is very subjective-and you are more qualified to make that subjective judgement than I am.

As you pointed out the chief down side of the shunt is finding a way to prevent getting shocked while connecting it.  The only two ways I can think of are 1.  Connecting all power connections last, or 2. using a NCVT to verify. I doubt power to the backline and/or FOH will be disconnected during a quick change over-and if you use an NCVT you effectively eliminate the need for the shunt-unless something fails during the performance.

You might consider a Diac shunt for simplicity-if you can find one that would handle the short circuit current, they typically have a threshold of 30 volts.

Of course, another option is to get the pricier option mandated by code for stage use to increase the demand ;D.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 28, 2014, 09:45:09 pm
It is not surprising that a more robust, comprehensive solution costs more than a solution that primarily protects against one failure mode-but the value of each is very subjective-and you are more qualified to make that subjective judgement than I am.
While there may be some debate, in my judgement shunting the two safety grounds together will protect against all of the sundry hazards I enumerated, while it counts on the mains power circuit breakers to trip from over current.
Quote

As you pointed out the chief down side of the shunt is finding a way to prevent getting shocked while connecting it.  The only two ways I can think of are 1.  Connecting all power connections last, or 2. using a NCVT to verify. I doubt power to the backline and/or FOH will be disconnected during a quick change over-and if you use an NCVT you effectively eliminate the need for the shunt-unless something fails during the performance.

Actually a practical way is to add a switch so the two grounds are not shunted until the switch is closed completing the circuit between the two grounds. Of course the cable jockey needs to be careful about touching the mic cable ground and guitar cable ground at the same time. Of course the downside to the shunt having an off switch is that operator may open the switch to reduce hum, if the grounds are more than the several volts apart that the diodes account for, and hum happens. 

Quote
You might consider a Diac shunt for simplicity-if you can find one that would handle the short circuit current, they typically have a threshold of 30 volts.
Think about it, current is not the problem as much as power dissipation. 20A x 30V is 600W. So any diac will quickly turn into a puddle of melted or vaporized silicon. I'll stay with my diode bridges, I have tested them with 120V  across them and they survive taking out a typical fuse/breaker.
Quote
Of course, another option is to get the pricier option mandated by code for stage use to increase the demand ;D.
no... that would be government over reach... while I wouldn't mind GFCI in bar outlets.

I may be imagining a problem that isn't really serious. If more musicians were killed, we might see more electrical building inspectors that know what they are doing to prevent problems. The last one we heard about was in Argentina and not to stereotype, but who knows what kind of electrical inspections they have.

A possible market for a high end box is for the money channel... Big name talent can afford the insurance for not getting zapped while using their favorite gear... While how many of them are still on wired mics?

So chicken egg... the guys who can afford it don't need it, and the guys who need it can't (won't) pay for it.

Still an interesting mental exercise.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on December 28, 2014, 11:37:26 pm
While there may be some debate, in my judgement shunting the two safety grounds together will protect against all of the sundry hazards I enumerated, while it counts on the mains power circuit breakers to trip from over current.
Actually a practical way is to add a switch so the two grounds are not shunted until the switch is closed completing the circuit between the two grounds. Of course the cable jockey needs to be careful about touching the mic cable ground and guitar cable ground at the same time. Of course the downside to the shunt having an off switch is that operator may open the switch to reduce hum, if the grounds are more than the several volts apart that the diodes account for, and hum happens. 
Think about it, current is not the problem as much as power dissipation. 20A x 30V is 600W. So any diac will quickly turn into a puddle of melted or vaporized silicon. I'll stay with my diode bridges, I have tested them with 120V  across them and they survive taking out a typical fuse/breaker. no... that would be government over reach... while I wouldn't mind GFCI in bar outlets.

I may be imagining a problem that isn't really serious. If more musicians were killed, we might see more electrical building inspectors that know what they are doing to prevent problems. The last one we heard about was in Argentina and not to stereotype, but who knows what kind of electrical inspections they have.

A possible market for a high end box is for the money channel... Big name talent can afford the insurance for not getting zapped while using their favorite gear... While how many of them are still on wired mics?

So chicken egg... the guys who can afford it don't need it, and the guys who need it can't (won't) pay for it.

Still an interesting mental exercise.

JR


Bear with me please - something isn't clicking.
Am I correct that JR is connecting two separate grounds through diodes, the theory that once the safety ground differential goes >2v, the grounds connect either to bleed off voltage to the side with lower potential, or if the difference is great enough, trip some other safety device upstream?
This "device" would be on the AC line, correct?
Here is my confusion - the "poor man's distro". http://www.triktags.com/power.htm Two separate circuits (hopefully) with grounds bonded to reduce the possibility of ground loops.
Are you suggesting something like a "poor man's distro" except instead of direct bonding, some type of diode arrangement would be used?
Am I missing something?
As a side question, what would happen if the "poor man's distro" were plugged into a correctly wired outlet and the second being RPBG?  Dead short right then and there, correct?  What about arc flash? 


Am I hopelessly wrapped around the axle here?
frank


ps.  I do appreciate all the mental horsepower being spent - I believe more than a mental exercise.  I would like to be able to say no one will be electrocuted on any of my stages. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on December 29, 2014, 12:02:18 am

 I would like to be able to say no one will be electrocuted on any of my stages.

Actually I can think of a number of folks I would pay to see electrocuted on stage.  However as I don't think I would do well in prison I will leave that to the guy upstairs (not the one in the spot loft).

Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 29, 2014, 12:31:57 am
Arc flash depends on the capacity of the feed.  If we are talking about RPBG, then hopefully we are well below that.

If the fault would have been cleared by tripping a breaker, save for the lack of a common ground between FeedA and FeedB, then adding a should-really-be-redundant ground connection would seem like a simple answer.

Grounding the racks to each other should be done before energising either feed obviously.  Otherwise we're just killing the tech instead of the muso.

A distro that ties the grounds together also seems to fix the problem.
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on December 29, 2014, 03:41:01 am
Actually I can think of a number of folks I would pay to see electrocuted on stage.


We could have a button to press at FOH for when they do something wrong - like in that episode of The Simpsons!


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 29, 2014, 10:08:34 am

Bear with me please - something isn't clicking.
Am I correct that JR is connecting two separate grounds through diodes, the theory that once the safety ground differential goes >2v, the grounds connect either to bleed off voltage to the side with lower potential, or if the difference is great enough, trip some other safety device upstream?
exactly
Quote
This "device" would be on the AC line, correct?
Actually between mic pin 1 and guitar cord sleeve... One a console ground and the other the guitar amp chassis. Both should be connected to their respective mains grounds, but aren't always.
Quote
Here is my confusion - the "poor man's distro". http://www.triktags.com/power.htm Two separate circuits (hopefully) with grounds bonded to reduce the possibility of ground loops.
Not to veer off topic but bonding the distro grounds together can actually create a loop, but loops are not the real problem, ground potential voltage differences are, and bonding the grounds together manages that.  BTW maybe teach them how to spell "bus" also, unless they use buss fuses inside... :P
Quote
Are you suggesting something like a "poor man's distro" except instead of direct bonding, some type of diode arrangement would be used?
Yes and no... I am not directly messing with the FOH power drop ground or the back-line power drop ground. One step removed and loosely bonding  (through diodes) the mic ground to the guitar ground. These are the points of contact for the musicians to electrical faults. A poor man's disto will not protect against a rouge guitar amp, but a poor mans distro "and" a GFCI should.
Quote
Am I missing something?
nah
Quote
As a side question, what would happen if the "poor man's distro" were plugged into a correctly wired outlet and the second being RPBG?  Dead short right then and there, correct?  What about arc flash? 
yup... but as long as your fingers aren't touching the blades of the plug, it should just take out the breaker for the RPBG branch.
Quote

Am I hopelessly wrapped around the axle here?
frank


ps.  I do appreciate all the mental horsepower being spent - I believe more than a mental exercise.  I would like to be able to say no one will be electrocuted on any of my stages.
I know that modern guitar amp design is much safer, has been for decades. Wiring practices in many venues is still suspect as evidenced by the singer/guitar player in Argentina recently. The fact that we are not reading about musician deaths every weekend here suggests that this is mostly under control, but not completely. Statistically playing and singing on stage is probably safer than driving your car to the gig.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on December 29, 2014, 10:19:49 am
I was pulling the 4 diode drops (roughly 2.4V peak) out of thin air... do you think I need to go to 3x or 4x bridges (4.8V) to be safe? I don't want to conduct current between safety grounds unless there is a hazardous fault, to keep the audio clean.

For human safety 5V is nothing, and as soon as the diodes heat up and melt they fail as dead shorts anyhow...

JR

JR, some 35 years ago I was able to solve ground-loop hum problems in my band's sound system by using back-to-back 5 volt Zener diodes (BIG ones) to isolate the ground path of the bass guitar amp. So 20+ years after I did that, Ebtech came out with their Hum-X product which uses a pair of reversed/paralleled silicon diodes that begin conducting around 0.5 volts. I've found that the Hum-X product will stop ground loop hum in some cases of small ground loop voltage differentials (GLVD's?), but doesn't help with a lot of larger voltages.

As you've noted earlier, if everything was wired correctly we wouldn't have to worry about this topic, but we all know that's a pipe dream. I was as a church in Dover, DE yesterday conducting a Tune-Up session on a sound system and found one Crown power amp for the monitors humming with a ground loop like crazy. Others amps in the rack weren't humming, so I tried adding a WW ISO box to the XLR feed which stopped the hum perfectly. I didn't have time to do an end-to-end voltage check, but a quick clamp-ammeter test showed around 1 ampere of current in the shield without an iso transformer. Previous tests on my bench suggest around 1 amp of ground loop current per volt of GLVD (Ground Loop Voltage Differential), so I'm thinking there was at least 1 volt difference in the grounds. I also suspect this was isolated to a single outlet which could easily have been caused by swapped neutral and ground wires. Now, I wasn't there to evaluate their power system and had a stage full of musicians to train, so I didn't have time for a full evaluation of their power distro. But I'm pretty sure that something like that was the cause. The key point is that whatever you do that cross-connects the grounds of a stage amp and the mixing console, which will almost certainly be powered by different receptacles, needs to operate with at least several volts of GLVD without producing ground loop currents and potential hum. My WAG is up to 5 volts GLVD blocking would be required before creating hum or a fail/tripping condition.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on December 29, 2014, 10:57:16 am
Ding! Thanks, JR, for walking me through your thought process.  Makes much more sense now. 
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 29, 2014, 11:03:46 am
JR, some 35 years ago I was able to solve ground-loop hum problems in my band's sound system by using back-to-back 5 volt Zener diodes (BIG ones) to isolate the ground path of the bass guitar amp.
Yup me too... back on the '70s I used some diode bridges between chassis and circuit grounds in a rack mount studio product to prevent corruption from the sundry stray ground currents coming from other rack mount products in the same rack.

Power zeners might work, there needs to be enough mass to them that they don't vaporize before the main breaker trips. Small diodes will not hang when exposed to full mains voltage. 
Quote
So 20+ years after I did that, Ebtech came out with their Hum-X product which uses a pair of reversed/paralleled silicon diodes that begin conducting around 0.5 volts. I've found that the Hum-X product will stop ground loop hum in some cases of small ground loop voltage differentials (GLVD's?), but doesn't help with a lot of larger voltages.
I contacted them privately a few years ago and suggested that they use more robust diodes (and/or get UL involved, who would test for reliability.) I never heard back from them, but in the '80s,  I had the Peavey agency guy ask UL about this and they were very receptive, but I was not willing to invest the ten's of $k to open a UL file and prove the approach with formal testing. Ground noise can be managed using proper input and output circuit designs while safely bonding the chassis to mains ground, so no need to fix a non-problem. 
Quote
As you've noted earlier, if everything was wired correctly we wouldn't have to worry about this topic, but we all know that's a pipe dream. I was as a church in Dover, DE yesterday conducting a Tune-Up session on a sound system and found one Crown power amp for the monitors humming with a ground loop like crazy. Others amps in the rack weren't humming, so I tried adding a WW ISO box to the XLR feed which stopped the hum perfectly. I didn't have time to do an end-to-end voltage check, but a quick clamp-ammeter test showed around 1 ampere of current in the shield without an iso transformer. Previous tests on my bench suggest around 1 amp of ground loop current per volt of GLVD (Ground Loop Voltage Differential), so I'm thinking there was at least 1 volt difference in the grounds. I also suspect this was isolated to a single outlet which could easily have been caused by swapped neutral and ground wires. Now, I wasn't there to evaluate their power system and had a stage full of musicians to train, so I didn't have time for a full evaluation of their power distro. But I'm pretty sure that something like that was the cause. The key point is that whatever you do that cross-connects the grounds of a stage amp and the mixing console, which will almost certainly be powered by different receptacles, needs to operate with at least several volts of GLVD without producing ground loop currents and potential hum. My WAG is up to 5 volts GLVD blocking would be required before creating hum or a fail/tripping condition.

Thanks, I'll take that under advisement.

I have continued to think about the premium (smart outlet strip) solution and this is not cheap or trivial. Even with a microprocessor it isn't trivial to detect all the possible errors. My current thinking is to test for any bootleg ground (not simple) and warn if that is detected. If significant voltage or current is detected between the mains and equipment grounds the relay opens or never closes. I suspect this is too expensive, and market to small for this to ever happen, but fun to think about.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on December 29, 2014, 09:25:29 pm

 no... that would be government over reach... while I wouldn't mind GFCI in bar outlets.
 
So chicken egg... the guys who can afford it don't need it, and the guys who need it can't (won't) pay for it.

Still an interesting mental exercise.


Unfortunately people who can't (won't) take responsibility for their own  well being are too often the justification for government over reach.

I agree about the mental exercise-and hopefully the discussion will raise awareness and understanding among others.

As for the GFCIs for backline-I am curious how many of these venues are required to have periodic safety inspections?  It would be a minimal additional check to use a tester like my local/state inspectors use on every new recept in new construction.  I don't have as much problem with government "overreach" when they are mandating the landlord/venue meet certain standards to protect the tenant/customer.  It might help to pursue raising awareness of this hazard among the inspectors through the  Association of Electrical Inspectors.
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on December 30, 2014, 01:38:14 am
If you like GFCI/RCD, bring your own.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 01, 2015, 01:28:14 pm


I have continued to think about the premium (smart outlet strip) solution and this is not cheap or trivial. Even with a microprocessor it isn't trivial to detect all the possible errors. My current thinking is to test for any bootleg ground (not simple) and warn if that is detected. If significant voltage or current is detected between the mains and equipment grounds the relay opens or never closes. I suspect this is too expensive, and market to small for this to ever happen, but fun to think about.

JR

Thinking some more about a premium outlet strip... I can source a 3 pole 10A relay so if any fault is detected before closing the relay doesn't close, and power never comes on. The unit will have an internal power supply so it can indicate the nature of the no-start fault. If in use it detects X mA of ground current it will open and stay latched off until reset. 

If we break line, neutral and ground, this should protect against all anticipated hazards. 

It may be interesting to hear what UL thinks about breaking the safety ground on purpose. The entire safety ground bonding rationale is based on shunting live faults to trip the associated breaker.

My cheapo mic ground to guitar ground diode shunt is consistent with the UL philosophy to take out the associated breaker.  My smart premium outlet strip with relay that releases ground (and power), may protect the meat sock from immediate hazard, and since it turns off the power, it will be hard (and ignorant) to just ignore.   

JR

PS: not cheap... onsey twosey.. relay is $25, suitable PS is probably around $20, GFCI outlet is probably the cheapest component. Micro only a couple dollars but PCB and glue $10. I may dummy one up just for fun, but ironically I don't have a grounded outlet in my house to test it with.  :o :o
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on January 01, 2015, 01:36:15 pm
Unfortunately people who can't (won't) take responsibility for their own  well being are too often the justification for government over reach.

I agree about the mental exercise-and hopefully the discussion will raise awareness and understanding among others.

As for the GFCIs for backline-I am curious how many of these venues are required to have periodic safety inspections?  It would be a minimal additional check to use a tester like my local/state inspectors use on every new recept in new construction.  I don't have as much problem with government "overreach" when they are mandating the landlord/venue meet certain standards to protect the tenant/customer.  It might help to pursue raising awareness of this hazard among the inspectors through the  Association of Electrical Inspectors.

I'm all for the government keeping people from being subject to abjectly stupid conduct, especially remembering that the Codes and regulations tend to be developed with the input of industry(ies) and then adopted by the various levels of government.  The NFPA has zero authority, likewise UL... but if your state, city or county adopts the codes or standards of either, you'll comply or....

Frankly I'm over pissy guitarists who hear shit that nobody else can hear (except other guitarists suffering from confirmation bias - sure the Emporer's new clothes are great!) and if their old gear kills them I'm *almost* fine with it if it happens because they're either cheap or paranoid about anything that changes their perceived "magic sound."  I love the instrument but some of its players are just batshit whacky, abusive or possibly mentally ill.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 01, 2015, 01:50:24 pm
I'm all for the government keeping people from being subject to abjectly stupid conduct, especially remembering that the Codes and regulations tend to be developed with the input of industry(ies) and then adopted by the various levels of government.  The NFPA has zero authority, likewise UL... but if your state, city or county adopts the codes or standards of either, you'll comply or....

Frankly I'm over pissy guitarists who hear shit that nobody else can hear (except other guitarists suffering from confirmation bias - sure the Emporer's new clothes are great!) and if their old gear kills them I'm *almost* fine with it if it happens because they're either cheap or paranoid about anything that changes their perceived "magic sound."  I love the instrument but some of its players are just batshit whacky, abusive or possibly mentally ill.

Yes but the customer is always right... If we can let the pissy guitar player plug his legacy POS amp into a smart outlet strip that protects him, without coming close to affecting his "tone" that should be all good... If it protects against rouge hot mic's too, all the better. 

Still not a commercial product IMO

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on January 01, 2015, 02:04:54 pm
Yes but the customer is always right... If we can let the pissy guitar player plug his legacy POS amp into a smart outlet strip that protects him, without coming close to affecting his "tone" that should be all good... If it protects against rouge hot mic's too, all the better. 

Still not a commercial product IMO

JR

There is enough of this - killing or injuring players with dodgy gear, the occasional minister electrocuted in "hot" baptismals - that one would think the public would demand compliance with or the creation of, Codes and regulations.  But nope, when building codes/electrical codes are only enforced when legitimate contractors or qualified individuals pull permits and get inspected (and inspectors are a whole 'nuther matter), people will die, buildings will burn... and as soon as the bodies are buried the countdown of forgetfulness starts.

And the last part, John, is why I'm cynical.  The great umbrage that happens each time this occurs dissipates within a very short time; until the next wardrobe malfunction or celebrity rehab intake.  Basically nobody but us (and the few like-minded individuals around the world) give a damn if these folks have died for no reason.  It's a product that too few can see a reason for existence, while standing of the bodies of the dead.

Hmmm.  Maybe I need another coffee.  Naw, I'm hitting "post."
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 01, 2015, 02:23:39 pm
I'm all for the government keeping people from being subject to abjectly stupid conduct, especially remembering that the Codes and regulations tend to be developed with the input of industry(ies) and then adopted by the various levels of government.  The NFPA has zero authority, likewise UL... but if your state, city or county adopts the codes or standards of either, you'll comply or....


In general, I tend to lean away from government mandates.  However, when the potentially harmed party is a third party I find the primary party often just asks "How cheap and will it work."  My personal definition of "work" by default includes the requirement that to be safe-but another contractor might well be willing to use a different definition and do it cheaper.  This is particularly aggravating to me when it comes to residential landlords-often they make decent money renting, but allow families to live in hazardous conditions they would not subject their own families to.

In this case, it only seems to make good economic sense.  It would be more cost effective for an inspector doing a safety inspection (assuming that already happens) to own and use an appropriate high quality tester to verify that receptacles are wired correctly than for every musician to have to own such a tester.  If the venue knows they will be tested, flagged and required to remedy shoddy work, soon enough they (hopefully) will decide it is better to do it once correctly than to pay for it twice.

In Iowa, the state will do a non mandatory inspection for $25-no government agency I deal with charges more than $50 for an inspection. If that kind of annual cost will make or break a venue,   IMO they are probably already broken.

What kind of value do we put on safety?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 01, 2015, 02:59:03 pm

And the last part, John, is why I'm cynical.  The great umbrage that happens each time this occurs dissipates within a very short time; until the next wardrobe malfunction or celebrity rehab intake.  Basically nobody but us (and the few like-minded individuals around the world) give a damn if these folks have died for no reason.  It's a product that too few can see a reason for existence, while standing of the bodies of the dead.

Hmmm.  Maybe I need another coffee.  Naw, I'm hitting "post."

I try to look at the world through economist eyes and we need to attempt to attach some perspective to the number of deaths from sundry causes. It is the nature of the human condition to respond to threats based on perception of being similarly affected personally combined with the megaphone effect of modern media that specializes in trying to scare viewers with news reports. a musician electrocuted on stage will briefly be in the spotlight because of celebrities getting disproportionate attention but the likelihood of viewers getting electrocuted by a mic and/or guitar are less likely than being hit by lightning. (33 killed by lightning in 2013). 

Bathtub or kitchen shocks are more likely and regulations have stepped up to meet that threat with GFCI outlets. 

I have always taken human safety seriously in association with product design and have long wrested with this "ground equals good" or "ground equals bad" conundrum.

I don't expect this two branch exposure scenario to rise to UL's taking action, since it involves an already illegal RPBG situation or a faulty ungrounded guitar amp. Leaky old guitar amps are already managed effectively with stock GFCI, and any musician who is unwilling to investing in personal GFCI to protect themselves deserves what they get.

A sound provider can use stock GFCI for back line to protect musicians from themselves. I probably would. I bought a cheap GFCI protected outlet extender (<$30) and may give it to a local musician when I'm finished playing with it. 

JR

PS: I wonder how many outlets are professionally tested with the 3 lamp testers that do not reveal RPBG? NCVT require some judgment to interpret due to false positives so I don't trust these as comprehensive remedies. Unless the inspectors approve the musicians back line gear too, I prefer the "here, plug into this outlet and you will be OK" approach. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 01, 2015, 03:22:31 pm
PS: I wonder how many outlets are professionally tested with the 3 lamp testers that do not reveal RPBG? NCVT require some judgment to interpret due to false positives so I don't trust these as comprehensive remedies. Unless the inspectors approve the musicians back line gear too, I prefer the "here, plug into this outlet and you will be OK" approach.

I have all the parts together to build my stinger-cap/isolated-ground/back-line/GFCI receptacle this weekend. It could be the simplest/affordable/legal solution to this problem since it would protect the musician from everything I can think of including plugging their stage amp into an RPBG outlet, using an ungrounded stage amp with power transformer leakage or a line-to-chassis short, and even touching a hot-mic from an improperly grounded PA while holding a properly grounded guitar. Plus, it just might be possible to have it NEC and/or UL approved or at least an exception qualified. This is the same design I've discussed before, but I'm adding a neon light between the incoming and outgoing EGC (safety ground) which should alert you of an RPBG-to-EGC fault with a grounded DI box during hookup, as well as a hot-mic PA condition, but only while the musician gets between the mic and the guitar. And it would also light up the hot-mic neon bulb if you touch properly grounded guitar strings to a hot mic. Meat-puppet fault currents would be limited to a max of 6 mA both ways, so while it could sting a bit it should be safe. I'll post pictures and come up with a few test scenarios to demonstrate and measure how well it works.

The beauty of this design is that it could be built into an add-on stringer box for PowerCon connected outlets like Whirlwind and others build, as well as added to basic Edison extension cords for smaller stages.

We shall see, but I think the design has possibilities.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 01, 2015, 03:34:33 pm
I am not suggesting a $5 3 lamp tester-rather a tester more like what Mike has suggested (which is in fact what the inspectors I deal with use)-or even better if you were able to design a smart outlet strip that could reliably detect a RPBG condition that same technology could be used for a tester. In that case, it makes more sense for one tester to be used in a preventative implementation on multiple venues rather than having every musician invest in a tester to  test every venue he plays in every time-though I do prefer the latter from a personal responsibility stand point.

That said, reliance on government inspection has too many potential holes for me to stake my life on.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 01, 2015, 05:11:52 pm
I have all the parts together to build my stinger-cap/isolated-ground/back-line/GFCI receptacle this weekend. It could be the simplest/affordable/legal solution to this problem since it would protect the musician from everything I can think of including plugging their stage amp into an RPBG outlet, using an ungrounded stage amp with power transformer leakage or a line-to-chassis short, and even touching a hot-mic from an improperly grounded PA while holding a properly grounded guitar. Plus, it just might be possible to have it NEC and/or UL approved or at least an exception qualified. This is the same design I've discussed before, but I'm adding a neon light between the incoming and outgoing EGC (safety ground) which should alert you of an RPBG-to-EGC fault with a grounded DI box during hookup, as well as a hot-mic PA condition, but only while the musician gets between the mic and the guitar. And it would also light up the hot-mic neon bulb if you touch properly grounded guitar strings to a hot mic. Meat-puppet fault currents would be limited to a max of 6 mA both ways, so while it could sting a bit it should be safe. I'll post pictures and come up with a few test scenarios to demonstrate and measure how well it works.

The beauty of this design is that it could be built into an add-on stringer box for PowerCon connected outlets like Whirlwind and others build, as well as added to basic Edison extension cords for smaller stages.

We shall see, but I think the design has possibilities.

The GFCI outlet strip with stinger cap ground is JR approvable. I like the neon lamp as a nice extra feature.  8)

(I have one GFCI strip on hand to modify while I have to buy a special screw driver to get it apart. It uses odd security screws.)

Non GFCI cords or outlet adapters with stinger grounds are not JR approvable. IMO the stinger cap is only really safe in combination with system GFCI/RCD). If an adapter could be used separately w/o the GFCI they probably will, so not completely safe.    >:(

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 01, 2015, 06:01:36 pm
The GFCI outlet strip with stinger cap ground is JR approvable. I like the neon lamp as a nice extra feature.  8)

(I have one GFCI strip on hand to modify while I have to buy a special screw driver to get it apart. It uses odd security screws.)

Non GFCI cords or outlet adapters with stinger grounds are not JR approvable. IMO the stinger cap is only really safe in combination with system GFCI/RCD). If an adapter could be used separately w/o the GFCI they probably will, so not completely safe.    >:(

JR

I'm also going with the idea of one Stinger-GFCI outlet per back-line stage amp. That way, any ground-fault leakages won't be additive from several back-line amplifiers. And if a guitar amp does trip a GFCI, it will only take out that single amp, not the entire back-line. Once I build and test the proof-of-concept design, then we can decide if it's affordable to build and if anyone will use it. But I think it's got all the "right stuff".
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on January 01, 2015, 06:14:43 pm
What I want is a VOM about the size/shape of a beer can that plugs into the end of a long electrical extension cord.  Ie, a tester that is referenced to another outlet.

Yes, I can do this with regular multimeter probes but it is fiddly.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 01, 2015, 07:35:57 pm
What I want is a VOM about the size/shape of a beer can that plugs into the end of a long electrical extension cord.  Ie, a tester that is referenced to another outlet.

Yes, I can do this with regular multimeter probes but it is fiddly.

I've actually designed such a gadget on paper, but didn't think it had enough general interest to be a commercially viable product. I guess JR is rubbing off on me... ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 01, 2015, 08:17:59 pm
But I think it's got all the "right stuff".

Including "JR Approval"-a step up from "UL Listing" methinks :D

If everything that had wiring to the stage-including FOH mixer-had the GFCI with stinger cap it would take multiple failures to cause an electrocution. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 01, 2015, 09:08:32 pm
Don't let me talk you out of any million dollar ideas... (psst this probably isn't one.)

JR

PS: I think I know the company to manufacture the MUSO outlet strip... I'd use "Stinger" in the name... But first lets make sure there are no snakes in the wood pile.

Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on January 01, 2015, 11:31:05 pm
Thinking some more about a premium outlet strip... I can source a 3 pole 10A relay so if any fault is detected before closing the relay doesn't close, and power never comes on. The unit will have an internal power supply so it can indicate the nature of the no-start fault. If in use it detects X mA of ground current it will open and stay latched off until reset. 

If we break line, neutral and ground, this should protect against all anticipated hazards. 

It may be interesting to hear what UL thinks about breaking the safety ground on purpose. The entire safety ground bonding rationale is based on shunting live faults to trip the associated breaker.

My cheapo mic ground to guitar ground diode shunt is consistent with the UL philosophy to take out the associated breaker.  My smart premium outlet strip with relay that releases ground (and power), may protect the meat sock from immediate hazard, and since it turns off the power, it will be hard (and ignorant) to just ignore.   

JR

PS: not cheap... onsey twosey.. relay is $25, suitable PS is probably around $20, GFCI outlet is probably the cheapest component. Micro only a couple dollars but PCB and glue $10. I may dummy one up just for fun, but ironically I don't have a grounded outlet in my house to test it with.  :o :o

Hi JR,
Given the brain storming request - FWIW this is what happens in industrial / mining applications for large equipment using trailing cables.

There is a control panel which contains the connection socket.

The control panel contains;

•   3 phase RCD (GFIC) protection.
•   AC detection for the earth (the screen in the cable)
•   Detection that the earth connection (and cable) has been made (there is a pilot wire in the training cable that provides the return circuit etc.)

If a fault is detected the control panel will not energise the equipment, or as you described latched off.

There is a requirement for routine inspection and testing, and things like earth resistance / leakage current are data-dogged.

There are other tricks used for very large installations where the supply star point is connected to ground through dynamic impedance. Under fault conditions the impedance is matched (complex opposite) to that of the fault. The potential at the fault is therefore greatly reduced. (a modern version of the Peterson coil)

http://www.connetics.co.nz/assets/Uploads/Technical-information.pdf





Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 02, 2015, 10:07:09 am
Thanks Peter... sounds like a good system to reduce risks in a hazardous environment. I have seen the shielded line cords with power cut-off, should leakage occur to the line cord shield, for sale by the company that makes GFCI outlet strips, but I've never seen them in use (AFAIK).

I fell like we will come up with an actionable plan by the end of 2015...To keep our guitar playing singers alive.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 02, 2015, 01:47:11 pm

Don't let me talk you out of any million dollar ideas... (psst this probably isn't one)


I am seeing more and more similarities between farmers and musicians.  Have yet to meet a farmer that can afford to have me wire something correctly-but almost never see a rusty combine working a field-they seem to always be able to afford a new one.  Given the cost of some of the vintage guitars/amps, would a $100-$150 safety device really break the bank?  Really?

Of course, there is always a cost vs benefit consideration-even on safety.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 02, 2015, 03:13:17 pm
I am seeing more and more similarities between farmers and musicians.  Have yet to meet a farmer that can afford to have me wire something correctly-but almost never see a rusty combine working a field-they seem to always be able to afford a new one.  Given the cost of some of the vintage guitars/amps, would a $100-$150 safety device really break the bank?  Really?

Of course, there is always a cost vs benefit consideration-even on safety.
Perhaps that is why seat belts and air bags and ABS brakes are mandatory, otherwise they would only be found on high end Mercedes.

I don't think we lose enough musicians to make this stuff mandatory, but GFCI and a smart ground lift might be a merchantable feature if engineered inside a premium (Mercedes) guitar amp.

JR

PS: I understand perceived cost benefit, I try to sell drum tuners to musicians with multi-thousand dollar drum kits, not willing to pay a couple hundred more to make them sound better.  :P  But the customer is always right.  ::)
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 02, 2015, 03:40:21 pm

I don't think we lose enough musicians to make this stuff mandatory....


Cost is measured in $, benefits in musicians-how many does it take to equal out? :o   Don't ask me during a soundcheck!!
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on January 03, 2015, 05:42:20 pm
I am seeing more and more similarities between farmers and musicians.  Have yet to meet a farmer that can afford to have me wire something correctly-but almost never see a rusty combine working a field-they seem to always be able to afford a new one.  Given the cost of some of the vintage guitars/amps, would a $100-$150 safety device really break the bank?  Really?

Very few of those shiny new combines were paid for with cash. Quite often only one payment is made per year: when the check from the co-op elevator comes in.

As an electrician, are you OK with waiting until next fall to be paid?

Granted, musicians aren't exactly in the same boat, but many are probably on the E-Z Payment Plan for their gear.

Besides, farmers and musicians don't see safety as a profit center.
Title: Re: brain storm an optimal human safety system for back line
Post by: Bob Leonard on January 04, 2015, 08:21:17 am
The two (2) words guitar players need to see are "Improves tone". So the model number for my safety device will be  - BLIT-FCB, or BLIT-MCB. Care to guess?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 04, 2015, 10:46:56 am
The two (2) words guitar players need to see are "Improves tone". So the model number for my safety device will be  - BLIT-FCB, or BLIT-MCB. Care to guess?

"Bob Leonard's Improved Tone- Female and Male Capacitor bypass"???  Close?

My only design goal is to "maintain" original tone, not improve it, while I guess the line cord phools may expect audible effects from messing with power ground connections.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 04, 2015, 10:54:23 am
The two (2) words guitar players need to see are "Improves tone". So the model number for my safety device will be  - BLIT-FCB, or BLIT-MCB. Care to guess?

IDK...  ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 10, 2015, 03:11:45 pm
I am still thinking about this and have distilled it down to a hot chassis microprocessor and a 3 pole relay.

When the outlet is powered up the microprocessor A/D inputs perform a NCVT measurement on the floating output side neutral and ground wrt the input side neutral. The micro inputs are high enough impedance that I should be able to tell the difference between a correct and reverse polarity power source. If it senses hot where neutral is supposed to be, it never turns on and the relay stays disconnected.

If it detects good power polarity the relay closes and applies power the GFCI protected outlets. Then the A/D convertor measures voltage drop across a modest resistance in series with the ground. This R can be much smaller impedance than a stinger cap since the relay will open up pretty quickly if it senses mA of ground path current.

I am not looking forward to breadboarding and debugging  a hot chassis design but that is the practical way to do this... a couple dollar micro, a PCB and some glue circuitry. The relay and GFCI outlets will be the most expensive parts, and not that bad for production(?).

About the only way this could be fooled is reversed mains power "and" hot ground on the outlet side, but I should be able to even catch that by NCVT probing the outlet side neutral.

So the plan is coming together... I still don't feel warm and fuzzy about this ever being a commercial product. And If the safe outlet strip refuses to power up, will the musicians just plug in around it (the show must go on)? Maybe I could build in a siren or crowbar clamp across the mains to take out the circuit breaker every time it detects reverse polarity power. :-) While that is electo-passive aggressive. RP is only dangerous in combination with BG.

JR

PS: Of course this is still conjecture until I build one and confirm that I can reliably make NCVT determinations with a cheap micro and outlet strip wiring. It will be easier to pick up an ambient ground with actual products plugged in.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on January 10, 2015, 07:59:41 pm
I am still thinking about this and have distilled it down to a hot chassis microprocessor and a 3 pole relay.

When the outlet is powered up the microprocessor A/D inputs perform a NCVT measurement on the floating output side neutral and ground wrt the input side neutral. The micro inputs are high enough impedance that I should be able to tell the difference between a correct and reverse polarity power source. If it senses hot where neutral is supposed to be, it never turns on and the relay stays disconnected.

If it detects good power polarity the relay closes and applies power the GFCI protected outlets. Then the A/D convertor measures voltage drop across a modest resistance in series with the ground. This R can be much smaller impedance than a stinger cap since the relay will open up pretty quickly if it senses mA of ground path current.

I am not looking forward to breadboarding and debugging  a hot chassis design but that is the practical way to do this... a couple dollar micro, a PCB and some glue circuitry. The relay and GFCI outlets will be the most expensive parts, and not that bad for production(?).

About the only way this could be fooled is reversed mains power "and" hot ground on the outlet side, but I should be able to even catch that by NCVT probing the outlet side neutral.

So the plan is coming together... I still don't feel warm and fuzzy about this ever being a commercial product. And If the safe outlet strip refuses to power up, will the musicians just plug in around it (the show must go on)? Maybe I could build in a siren or crowbar clamp across the mains to take out the circuit breaker every time it detects reverse polarity power. :-) While that is electo-passive aggressive. RP is only dangerous in combination with BG.

JR

PS: Of course this is still conjecture until I build one and confirm that I can reliably make NCVT determinations with a cheap micro and outlet strip wiring. It will be easier to pick up an ambient ground with actual products plugged in.
This sounds like the detection I suggested early in this thread by using an antenna and opamps to detect if 50/60hz is present on a single wire.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 10, 2015, 08:38:04 pm
This sounds like the detection I suggested early in this thread by using an antenna and opamps to detect if 50/60hz is present on a single wire.
That is kind of the principle of all NCVT but it isn't about op amps for voltage gain, but high enough input impedance to not load down electrostatic coupled environmental voltages. While a NCVT may have one real conductive lead, the weak coupled ground reference is coming from the device chassis-handle via very high impedance.
   
I am not adding voltage gain and don't care about the Hz. The microprocessor A/D inputs are pretty high impedance and decent resolution (3V/ 12bit). I will start out ASSuming that the mains wiring is correct polarity and ground the micro to neutral. I will cap couple into the A/D inputs and sniff for significant voltage. If the A/D is grounded to real neutral (0v) and I sniff other lines that should be close to 0V I should only get insignificant input voltage readings. OTOH if the outlet is reversed polarity the effective ground that the micro is using for comparison is now swinging 120V AC, when I then sniff some floating 0V lines like he not yet powered up outlet neutral, the weak 0V compared to the micro swinging 120V will now register as a measurable voltage (I hope).

If I sniff and all is good then I will connect power and use two of the A/D inputs to measure current flowing in the ground through a resistor. For this to work well ground  and neutral need to be within 3V of each other, but I can deal with them being even further apart if needed, since I measure both ends of the resistor and just subtract one end from the other.

The unknown to me is the sensitivity of the microprocessor A/D inputs. I need to cap couple through small enough capacitors that the current from them hitting the input clamps with full mains voltage doesn't melt silicon, while large enough to get useful readings (especially for the current sensing which will be mV not 100V).

I believe this will work.

JR
 
Title: Re: brain storm an optimal human safety system for back line
Post by: Don Boomer on January 12, 2015, 01:29:17 pm

So the plan is coming together... I still don't feel warm and fuzzy about this ever being a commercial product.

Not telling you anything you don't already know ... but how many $$$ would need to be added final cost to offset your liability for such a product? 

That said, I'd be happy to be a  beta tester.  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 12, 2015, 01:54:27 pm
Not telling you anything you don't already know ... but how many $$$ would need to be added final cost to offset your liability for such a product? 

That said, I'd be happy to be a  beta tester.  8)

Yes. there is a certain irony in liability exposure from trying to protect musicians from bad wiring. The good news is I do not see a chance in hell that this could ever be commercially successful (it's hard enough dragging drummers into the 21st century).

[edit]
Upon reflection the addition of a cut off relay and GFCI outlet into an outlet strip does not seem all that dangerous, the failure mode (relay did not open) would act just like a normal outlet strip, with GFCI. Of course any commercial product would need to be vetted by UL.

Customers still need to avoid dangerous situations even with extra protection devices in use.
[/edit]

If I reduce this to a working design (it still needs to be proved on the bench and code written) I will publish the details and share it for others to use.

This is academic if all mains wiring was properly done and vetted.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on January 16, 2015, 12:48:44 pm
This is academic if all mains wiring was properly done and vetted.

Until something changes... either an intentional modification to the electrical system (authorized or unauthorized) or damage such as water intrusion or corrosion, other physical abuse and damage, normal wear, or connecting faulty equipment that doesn't quite trip the OCPD/GFCI.

Point being, any vetting or certification is only valid for the date and time the examination happened. As time progresses, the risk increases, so the need for additional safety gear becomes more important.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 19, 2015, 11:44:29 am
Good news- bad news. Good news I am coming up with a workable plan for my smart outlet.

#1 test for floating ground.  (do not close relay?)
#2 test for reverse polarity   (do not close relay?)
#3 test for bootleg connection  (do not close relay?)
#4 test for current flowing in ground (open relay).

The bad news is coding the microprocessor brain involves running the processor in an emulator connected to a computer. I am very apprehensive about connecting my computer to a hot chassis design. Especially one capable of being connected to RPBG to detect the faulty wiring. 

I may have to rig up a floating transformer isolated prototype but this still seems a little dicey. I just researched buying a formal opto-isolated emulator rig from the microprocessor company I use and they want over $400  :( . A generic JTAG opto interface is probably $50 but then I would have to discover all the secret handshakes to get it working.

arghhh...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on January 19, 2015, 12:08:25 pm
Good news- bad news. Good news I am coming up with a workable plan for my smart outlet.

#1 test for floating ground.  (do not close relay?)
#2 test for reverse polarity   (do not close relay?)
#3 test for bootleg connection  (do not close relay?)
#4 test for current flowing in ground (open relay).

The bad news is coding the microprocessor brain involves running the processor in an emulator connected to a computer. I am very apprehensive about connecting my computer to a hot chassis design. Especially one capable of being connected to RPBG to detect the faulty wiring. 

I may have to rig up a floating transformer isolated prototype but this still seems a little dicey. I just researched buying a formal opto-isolated emulator rig from the microprocessor company I use and they want over $400  :( . A generic JTAG opto interface is probably $50 but then I would have to discover all the secret handshakes to get it working.

arghhh...

JR

That's a step backwards and I have nothing to offer.  Sounds like a good water cooler discussion, will bring it up at work today and see what everyone thinks.

I assume you have a ribbon cable to a card in the computer and then some type of processor emulator that plugs into your design board?

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 19, 2015, 12:43:39 pm
That's a step backwards and I have nothing to offer.  Sounds like a good water cooler discussion, will bring it up at work today and see what everyone thinks.

I assume you have a ribbon cable to a card in the computer and then some type of processor emulator that plugs into your design board?

Modern micro emulation is performed with a small hardware dongle that plugs into a PC USB port and then provides a (generic?) JTAG programming/emulation interface with the micro. Microprocessors with flash memory can be directly programmed this way, and run one clock step at a time for in circuit de-bugging.

The hardware dongle with an opto-isolator between it and the micro does not seem that exotic. It might run a little slower than a direct digital connection, and programming the flash may take a little more effort than just passing digital states back and forth. I ASSume this has all been sorted but not widely used, so a dedicated solution for my preferred micro family costs hundreds of dollars.

For that much money I am tempted to develop off-line, but this is harder, since I can't easily check the internal A/D measurement results, etc. Of course I could externally vary input stimulus and empirically determine thresholds.

JR   
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 19, 2015, 01:41:16 pm
Good news- bad news. Good news I am coming up with a workable plan for my smart outlet.

#1 test for floating ground.  (do not close relay?)
#2 test for reverse polarity   (do not close relay?)
#3 test for bootleg connection  (do not close relay?)
#4 test for current flowing in ground (open relay).

The bad news is coding the microprocessor brain involves running the processor in an emulator connected to a computer. I am very apprehensive about connecting my computer to a hot chassis design. Especially one capable of being connected to RPBG to detect the faulty wiring. 

I may have to rig up a floating transformer isolated prototype but this still seems a little dicey. I just researched buying a formal opto-isolated emulator rig from the microprocessor company I use and they want over $400  :( . A generic JTAG opto interface is probably $50 but then I would have to discover all the secret handshakes to get it working.

arghhh...

JR

As you have surmised, there will be numerous mis-wiring issues that you'll need to create on purpose to test your design, and a bunch of them would create dangerous currents back-flowing into your properly grounded computer. Of course, you could run this on a laptop with battery power. However, there will be several outlet fault conditions (RPBG being obvious) that would create a hot-chassis condition on your laptop. Probably would NOT blow up the laptop, but WOULD be deadly for anyone touching metal on the laptop and anything else earth grounded. I would considering using a plastic laptop and keep it isolated from everything else including no RJ-45 connections or USB printer hookups. Still, you'll need to be aware of the potential shock hazard to you if you get in the fault path. I would probably risk it myself, and you (JR) might be willing and knowledgeable enough to do it safety for testing. But I don't want anyone else on this forum creating a hot-chassis condition on purpose because of the risks involved.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 19, 2015, 11:29:49 pm
Even RPBG can be simulated on an isolated workbench with a circuit fed by a GFCI breaker.  Off the cuff, I'd say 90% of your testing could be done that way using a battery powered laptop though optical isolation would be a nice touch..  Final verification might best be done sans GFCI protection-but at that point you could reasonably do it wearing voltage rated gloves.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on January 20, 2015, 12:18:14 am
As you have surmised, there will be numerous mis-wiring issues that you'll need to create on purpose to test your design, and a bunch of them would create dangerous currents back-flowing into your properly grounded computer. Of course, you could run this on a laptop with battery power. However, there will be several outlet fault conditions (RPBG being obvious) that would create a hot-chassis condition on your laptop. Probably would NOT blow up the laptop, but WOULD be deadly for anyone touching metal on the laptop and anything else earth grounded.

Connect the laptop to the network via WiFi (no CATx ethernet needed). Then use Remote Desktop or VNC (or some other means) to access the laptop's desktop remotely in order to do the programming. Then you don't have to actually touch the laptop when the intentional faults are present.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 20, 2015, 11:13:23 am
The last time I fired up my old laptop it would not boot-up so I would have to fix it to use it, and then load up the emulation software and drivers...

I now have an alternate plan. Phase one I fire up my prototype with a low voltage floating power source to confirm the different test modes with faked stimulus. Phase two, I finish development running it hot chassis. If I use one of my old tuner PCBs as a prototype test platform I have two 12 LED meters that I can use to display different measured results so I can easily see what levels the microcomputer is getting from different faults, so I guess I can't use that as an excuse.  8)

Tests as I see them are

#1- is ground floating or bonded to neutral? With micro referenced to neutral drive a couple k ohm resistor into input side ground with relay open and read that ground voltage with one A/D input. If the ground is floating it will be easy to drive it up to 3V by the micro. Note: this A/D input is one of two used later to sense ground current.

If ground is floating outlet can still be used thanks to the GFCI but I probably won't. Make them find a grounded power drop so indicate open ground fault and stop there. 

#2  test for reverse polarity. With micro referenced to apparent input neutral, sniff the neutral connection on the still floating output side with an A/D input. If what is supposed to be a quiet input neutral is actually line (hot), the quiet output side neutral should register a not very quiet voltage wrt the micro that is referenced to hot. (this will work better with equipment plugged in, but may get a usable reading from outlet wiring, since the micro A/D input is relatively high impedance.  This is my DIY NCVT.     

Again reverse polarity by itself is not immediately dangerous but I might as well indicate the problem and prevent connection. In a price is no object product, another relay could correct the polarity while this gets a little hairy to keep the micro powered during the switch-over. If price is no object I don't need to make it hot chassis but the market drops exponentially with added cost so I will just indicate and refuse to connect power if any fault is found.   

#3- Test for bootleg ground. ASSuming we already passed tests one and two, so polarity is correct and ground is bonded, now switch in a couple amp load between mains line and neutral. To avoid dissipating hundreds of watts, this load can be pulsed on for only a few mSec at a time. This load should cause a small voltage step in both the line and neutral wiring. If the ground is bootlegged to neutral, it will move in lock step with the neutral so there will be no voltage step seen in the ground relative to neutral. If the ground wire is a separate run back to the panel, it will be unaffected by the pulsed load so there should be a measurable step voltage seen between neutral and ground (because neutral is the one changing).   

A bootleg ground is not immediately a shock hazard but wrong to leave it unchallenged, so again we can make the operator search out a proper outlet with proper ground. If the distro wiring is extremely low impedance this pulsed voltage artifact could be small. A tradeoff may exist between sensitivity of this measurement and protecting the A/D input from over current during a fault. 

#4 After passing tests one, two, and three, we are ready to switch on the power relay and connect the mains power to the GFCI outlet and output side. In this operational mode we will connect another A/D input to the output ground with a modest resistance between the input ground and output ground. The micro will look for a voltage difference between the two ends of the resistor to compute a current flow. When the arbitrary current threshold is exceeded the relay will latch open and indicate the ground current fault.

The GFCI will also trip and protect if any of it's line current does not return properly.

Note a hot output side ground will have a path to the input side neutral through the micro A/D so this input will need to be current limited with suitable large resistance to keep and fault current down in sub-lethal mA range.

JR

PS: Now I need to stop wanking get back to my day job...
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on January 20, 2015, 12:49:52 pm
Modern micro emulation is performed with a small hardware dongle that plugs into a PC USB port and then provides a (generic?) JTAG programming/emulation interface with the micro. Microprocessors with flash memory can be directly programmed this way, and run one clock step at a time for in circuit de-bugging.

The hardware dongle with an opto-isolator between it and the micro does not seem that exotic. It might run a little slower than a direct digital connection, and programming the flash may take a little more effort than just passing digital states back and forth. I ASSume this has all been sorted but not widely used, so a dedicated solution for my preferred micro family costs hundreds of dollars.

For that much money I am tempted to develop off-line, but this is harder, since I can't easily check the internal A/D measurement results, etc. Of course I could externally vary input stimulus and empirically determine thresholds.

JR   
There are so many creditcard prototype boards that run linux and like with all the gpio you'd want. You should be able to take a $35 raspberry pi (arm-based) and then use native gcc and gdb using SSH over wifi. Depending on how you write the code it should be portable...

While you are coding you could even monitor the mains voltage with what you probably already have in your design and any noise on the line and log this.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 20, 2015, 01:37:52 pm
There are so many creditcard prototype boards that run linux and like with all the gpio you'd want. You should be able to take a $35 raspberry pi (arm-based) and then use native gcc and gdb using SSH over wifi. Depending on how you write the code it should be portable...
I recognize about half that jargon...  Are you suggesting a wifi enabled prototype could be run in emulation mode wirelessly?

I am not interested is starting from scratch in a completely new development environment using an unfamiliar (to me) high level language. I generally code embedded applications using machine language. I have too many years and brain cells invested in my current comfort zone.

If it is actually that easy tell us how it works out. I drew you a map for how the different faults could be isolated and measured (hypothetically). 
Quote
While you are coding you could even monitor the mains voltage with what you probably already have in your design and any noise on the line and log this.
Yes I could monitor and meter line voltage while that was not in my original design brief that might be a merchantable extra feature that customers would value more than it cost to implement (a few LEDs).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank Koenig on January 20, 2015, 07:10:40 pm
I'm not saying the the Raspberry Pi is necessarily the best choice for this application, but I'll give this supportive anecdote. About 8 years ago a buddy and I built a little telemetry system for a remote home -- more-or-less a home-brew home-automation system. We used Windows XP running on a superannuated laptop and an industrial Ethernet data acquisition box. This works great to this day but we wanted to get away from the old laptop and its power issues and also get away from Windows.

The original code is all Java and my buddy ported it to the Raspberry Pi with remarkably little effort. We were up and running on the Pi in hours. I'm now in the process of designing a simple analog and digital interface board for the Pi using its 40 pin GPIO connection. Once I get that going we can ditch the Ethernet data acquisition system, too.

The Pi originally was developed for educational use but now has been widely adopted by all kinds of folks. A friend who works at an electronic hardware manufacturing company told me they use many in their production test fixtures, for example. The only thing that sucks about the Pi, in my opinion, is the the lack of any ordinary engineering documentation. It's as though its creators wanted the world to reverse engineer it and talk about it endlessly on Internet forums.

Anyway, Raspberry Pi is a solid, cheap, powerful little platform. I just ordered two more -- one might replace another old Windows PC as my "Internet radio receiver".

Best,

--Frank

PS: Forgot to say that we're using "Raspian" Linux on the Pi.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 30, 2015, 04:35:13 pm
Back on topic, I just got in the special security screw-head driver so I could take apart the commercial GFCI power strip/adapter. No surprises inside, I can see the current difference sense transformer and a pretty heavy duty electro mechanical circuit interrupter(?) . Two pcbs using cordwood construction (top and bottom PCB with parts between them.)

The big honking ground wire is a pass through and not connected to the GFCI boards so I should be able to break the ground without defeating the GFCI protection.

I am tempted to add a ground lift switch with a stinger cap in the lifted ground path. I don't recall hearing much feedback from the several interested guitar players on this thread about how effective the stinger cap is at reducing hum, but i should probably just test this myself. I was planning to give this away to some lucky local guitar player/singer after I am done with this particular investigation.

I may modify this one and drop in on a local bar band gig... Should take all of a couple minutes to confirm if the stinger cap works to manage mains noise. There are no FOH power drops in the small bar gigs I'm talking about so this is probably the optimal solution for them. They can keep using their dicey old guitar amp and not die.

The big dog relay and blinky lights is a premium product offered for sale to unappreciative cheap bastaads... (pearls before swine). This stinger GFCI could be cheap and easy (practical, sellable, etc).

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on January 30, 2015, 08:09:25 pm
The big dog relay and blinky lights is a premium product offered for sale to unappreciative cheap bastaads... (pearls before swine). This stinger GFCI could be cheap and easy (practical, sellable, etc). 

I agree. This old-school fix in combination with a GFCI is likely the best and simplest way to protect performers from every failure combination I can think of.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 03, 2015, 01:41:37 pm
Here is the guts of the commercial GFCI power drop.

Not much room inside, but I'm going to shoe horn in an on-off-on toggle switch for testing with a .047 uF stinger cap.. so the switch will select between ground connected, ground lifted, and ground connected through .047uF stinger cap.

I will use a 100V cap I had laying around since this is not a final version.  I think I can fit a proper Y cap inside this without a switch but first want some feedback regarding the cap's effectiveness at quieting any guitar rig plugged into it.

=========

I will order a proper Y cap after I work out a few details for something else I'm scribbling in my late night design musings. My latest thinking is that I might be able to make a solid state low mA sensitivity fuse with three power mosfets that can stand off 400V when open (devices are maybe $0.35 ea so not crazy) there will be some glue circuitry to turn on the fuse, and to latch it off when tripped. The fuse when on would have something like 100 ohms in series and detect the voltage drop across that 100 Ohms. Much lower Z than a stinger cap.

I am thinking instead of using a micro processor and relay for my smart outlet strip, perhaps this $1-2 dollar electronic ground fuse, a couple dollars worth of power triacs to switch on line and neutral. After start up testing and for as long as the sense circuits are happy it will connect power to the output side.

If the sense circuitry senses that neutral is hot using a non-contact sense circuit (as simple a small active device comparing neutral to some arbitrary environmental ground) a fault state is latched and the power triacs never turn on. If the ground fuse senses more than a few mA it likewise trips the triacs off and ground open.

If this works this is getting cheaper...and an open ground is safer than than even a stinger cap. The GFCI unit is the most expensive single part, but off the shelf GFCI outlets are not that expensive, and probably cheaper in quantity.

 OK back to my day job...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on February 03, 2015, 02:34:47 pm
I love to see this progress.  Thanks!  Keep up the good work!
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 03, 2015, 09:57:23 pm
Every so often, I see stand alone GFCI devices-look like a gfci recptacle, but no place to plug in anything-clearanced in the big box stores.  Pretty sure my local Menards had some clearanced for $6 or $7-these were P & S  not no name junk.

Just a thought, if you are needing some cheap experimenter devices.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 05, 2015, 12:17:18 pm
In my late night design sessions I am pondering the danger of boot strapping ground? I know the danger from a bootstrapped ground to neutral should that neutral open up, since ground would then become energized,,,, but if we have ground current sensing, and reverse polarity sensing, it seems that the open neutral would be detected and protected against.

I guess my question comes down to how to act if I plug into an outlet that is correct polarity but lacking a ground connection?

#1 blink a "no ground" LED but still work since GFCI will still work?
#2  or internally bootstrap the floating ground to neutral?

I am reluctant to just not work if open ground is detected since that will just encourage most users to bypass the safety device and plug into the unprotected outlet.
-------------
Likewise a reverse polarity with open ground should be safe to use with GFCI, so RP with floating ground should get a warning but work, RPBG would warn and not power up.
------------
RP with ground complicates my electronic ground fuse, but I may have a work around for that.
========
? Another question for Mike... How much voltage have you seen between real grounds and neutral? I should be able to ignore up to several volts of AC between them for my ground current sense, but do I need to?  I guess if I tolerate RP I need to ignore full voltage between should be neutral and is ground.

RPBG is killer, and BG is bad practice, but just BG with current/voltage sense and protection might be OK?

Cheapest and easiest to design is just not work at all if there is no ground or reverse polarity but I doubt that would stop players from plugging into rouge outlets. The show must go on... :o

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2015, 01:32:47 pm
? Another question for Mike... How much voltage have you seen between real grounds and neutral? I should be able to ignore up to several volts of AC between them for my ground current sense, but do I need to?  I guess if I tolerate RP I need to ignore full voltage between should be neutral and is ground.

So here's how to visualize G to Neutral voltage. Let's assume a properly wired system where the ground isn't carrying any current. Assume you're starting with 120 volts at the service panel. Without any current draw from the outlet you'll still have 120 volts there. So there's no voltage drop because there's no current, and there should be zero volts between the Ground and Neutral.

Scenario #1 is different though. Let's assume you have a big amplifier plugged into an outlet that's drawing significant current. And if the Hot to Neutral voltage drops down to 110 volts, then that's not all on the black wire. It's actually 5 volts on the neutral wire and 5 volts on the hot wire. So an outlet that bouncing between 120 and 110 volts on H-N with current draw should read between 0 and 5 volts G-N. That's normal and expected. When you DON'T read a fluctuating voltage between G-N that's 1/2 of the total drop under load, that's a sign that there's a bootleg ground. That's one really quick test I do on an outlet to quickly catch a bootleg ground. Put a DMM between Ground and Neutral. If it measures ANY voltage up to 5 volts, then it's NOT a bootleg ground. If it measures 0 volts (Zed for Steve, I think) then there might be no load on that leg, so throw a 1,000 space heater or PAR light on the same outlet and look for a voltage rise between G and N. If it does NOT rise to 1/2 of the total drop, then it's a bootleg ground. If it DOES rise, then it's NOT a bootleg ground.

One other thing you would like to catch in your tester is swapped Neutral and Ground wires. Happens a lot more than one would expect and causes all sorts of ground loop hum that varies under load. This is the basis of my hypothesis on GLID (Ground Loop Inter-modulation Distortion).   
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 05, 2015, 02:07:49 pm
So here's how to visualize G to Neutral voltage. Let's assume a properly wired system where the ground isn't carrying any current. Assume you're starting with 120 volts at the service panel. Without any current draw from the outlet you'll still have 120 volts there. So there's no voltage drop because there's no current, and there should be zero volts between the Ground and Neutral.
Got you... My plan is to handle a couple back line units so hopefully not that much current but yes I need to tolerate 10V or more.
Quote
Scenario #1 is different though. Let's assume you have a big amplifier plugged into an outlet that's drawing significant current. And if the Hot to Neutral voltage drops down to 110 volts, then that's not all on the black wire. It's actually 5 volts on the neutral wire and 5 volts on the hot wire. So an outlet that bouncing between 120 and 110 volts on H-N with current draw should read between 0 and 5 volts G-N. That's normal and expected. When you DON'T read a fluctuating voltage between G-N that's 1/2 of the total drop under load, that's a sign that there's a bootleg ground. That's one really quick test I do on an outlet to quickly catch a bootleg ground. Put a DMM between Ground and Neutral. If it measures ANY voltage up to 5 volts, then it's NOT a bootleg ground. If it measures 0 volts (Zed for Steve, I think) then there might be no load on that leg, so throw a 1,000 space heater or PAR light on the same outlet and look for a voltage rise between G and N. If it does NOT rise to 1/2 of the total drop, then it's a bootleg ground. If it DOES rise, then it's NOT a bootleg ground.
This gets me back to my microprocessor where I could switch in a test load and look at all three lines. I lean toward very briefly pulsing a load for maybe one cycle to keep heat dissipation low. But this is getting more expensive not less.
Quote
One other thing you would like to catch in your tester is swapped Neutral and Ground wires. Happens a lot more than one would expect and causes all sorts of ground loop hum that varies under load. This is the basis of my hypothesis on GLID (Ground Loop Inter-modulation Distortion).
Again this requires the smarter microprocessor approach.  I was mainly focussed on low cost safety mitigation rather than a full boat tester, but that may be a different market. 

[edit] Ok, is that a trick question? I do not know how to test for swapped ground-neutral in a single outlet. If the impedance of the ground wire is reasonable it will test and act like neutral would relative to that outlet. The problem with swapped neutral-ground is mainly the cross contamination to the ground quality elsewhere, and neutral to the local ground. 

I guess you could sniff the ground and neutral before you start testing for which one is quieter but what do you use for your 0V reference? It's hard enough to sniff for a polarity swap without a solid ground reference, trying to parse out mV of noise on ground vs, neutral before you connect will be difficult.  I'll think about this but It seems hard.   [/edit]

What do you think about the lesser hazard of bootleg connection when ground current and/or polarity sensing is used? 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on February 05, 2015, 05:48:35 pm
I just wanted to mention that I bought a socket safety tester today. It is branded with a swedish company logo but is possibly some OEM.

It tests voltage on earth connection, broken earth wire, broken neutral wire, broken live wire, interchanged neutral and live, interchanged earth and live, interchanged earth and live with broken earth, function test of RCCB 30mA, what pin of the socket is live.

Only thing it can't detect is interchanged neutral wire and earth wire.

http://www.malmbergs.com/frmProductDisplay_new.aspx?item=4200450
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2015, 05:59:51 pm
I just wanted to mention that I bought a socket safety tester today. It is branded with a swedish company logo but is possibly some OEM.

It tests voltage on earth connection, broken earth wire, broken neutral wire, broken live wire, interchanged neutral and live, interchanged earth and live, interchanged earth and live with broken earth, function test of RCCB 30mA, what pin of the socket is live.

Only thing it can't detect is interchanged neutral wire and earth wire.

http://www.malmbergs.com/frmProductDisplay_new.aspx?item=4200450

I'll bet you a 6-pack of the beer of your choice or a dozen donuts that it won't find an RPBG (Reverse Polarity Bootleg Ground). See http://ecmweb.com/contractor/failures-outlet-testing-exposed (http://ecmweb.com/contractor/failures-outlet-testing-exposed)

Without an external ground reference there's no way for it to know if the Hot is at zero volts above earth, and the Ground and Neutral are both at 120 volts (or 230 volts in Europe).
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on February 05, 2015, 06:12:23 pm
I'll bet you a 6-pack of the beer of your choice or a dozen donuts that it won't find an RPBG (Reverse Polarity Bootleg Ground). See http://ecmweb.com/contractor/failures-outlet-testing-exposed (http://ecmweb.com/contractor/failures-outlet-testing-exposed)

Without an external ground reference there's no way for it to know if the Hot is at zero volts above earth, and the Ground and Neutral are both at 120 volts (or 230 volts in Europe).
They have added a touch point similar to neon-based 'screwdriver' tester that will act as a reference point for RPBG testing. By touching that PE-test point it will tell you if your ground is live.

I've not seen that feature on any other socket tester until today...
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2015, 06:30:54 pm
They have added a touch point similar to neon-based 'screwdriver' tester that will act as a reference point for RPBG testing. By touching that PE-test point it will tell you if your ground is live.

I've not seen that feature on any other socket tester until today...

Is there an English (or American) version of this website? If what you say is true, then that's a real step forward in outlet testing. Do you want beer or donuts???  ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 05, 2015, 08:56:00 pm
Technically, I don't see a safety issue with a bootleg neutral IF you are testing for ground current and  RP.  However, liability wise, if you create a bootleg ground and something fails in your testing you have just put a big target on your back.
 
I commonly hear from electrical inspectors "don't make a non-conforming situation worse, or into another non-conforming situation", but you can leave it as is.

The other possibility is interconnection.  Say your receptacle has no ground so you bootleg-but the guitar amp is connected to a DI that is connected to a mixer that has a ground from another receptacle, now neutral current from your receptacle has another path to ground which may lead to nuisance trips-not necessarily unsafe, but maybe enough to make your device unusable.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 05, 2015, 10:03:13 pm
Technically, I don't see a safety issue with a bootleg neutral IF you are testing for ground current and  RP.  However, liability wise, if you create a bootleg ground and something fails in your testing you have just put a big target on your back.
 
I commonly hear from electrical inspectors "don't make a non-conforming situation worse, or into another non-conforming situation", but you can leave it as is.

The other possibility is interconnection.  Say your receptacle has no ground so you bootleg-but the guitar amp is connected to a DI that is connected to a mixer that has a ground from another receptacle, now neutral current from your receptacle has another path to ground which may lead to nuisance trips-not necessarily unsafe, but maybe enough to make your device unusable.

Good point... the low liability way is to just not work if anything is not perfect.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on February 06, 2015, 03:45:39 am
Is there an English (or American) version of this website? If what you say is true, then that's a real step forward in outlet testing. Do you want beer or donuts???  ;D
I think I was able to find the actual manufacturer: http://www.dyinstrument.com/duoyi/?q=socket_polarity_tester_RCD/DY207

The common name seems to be dy207 and with a letter at the end to differentiate it from different test configurations.

Here is the product manual. The english version is in the last pages:
http://www.malmbergs.com/docs/ba/4200450.pdf

My only grief about it is that you still need to interpret a led matrix. I'd like it to be more easy and failsafe to read out, with multi color leds to reduce operator error, where red is an error condition and green is OK.

While I like beer (ice-cold kilkenny and/or guinness) I think that I'll have at least one donut with them  :P
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 06, 2015, 07:55:06 am
I think I was able to find the actual manufacturer: http://www.dyinstrument.com/duoyi/?q=socket_polarity_tester_RCD/DY207

The common name seems to be dy207 and with a letter at the end to differentiate it from different test configurations.

Here is the product manual. The english version is in the last pages:
http://www.malmbergs.com/docs/ba/4200450.pdf

My only grief about it is that you still need to interpret a led matrix. I'd like it to be more easy and failsafe to read out, with multi color leds to reduce operator error, where red is an error condition and green is OK.

While I like beer (ice-cold kilkenny and/or guinness) I think that I'll have at least one donut with them  :P

Robert, this is excellent. I've posted a pic of the relevant part of the manual in english. This appears to be a basic 3-light neon tester with an additional neon light connected between the ground contact and an external finger contact. We've discussed the use of a neon bulb for testing hot grounds, so this should work. Of course, this particular tester is for 230 volts only and won't fit an American "Edison" plug, but it should be possible to retrofit an extra neon bulb into a standard 3-light 120-volt Edison outlet tester. The real question is can this tester be UL listed since it could possibly expose the person performing the test to lethal current if the neon bulb and its current limiting resistor both shorted out. Yeah I don't think that double failure mode would be possible, but UL is funny about that sort of thing. What do you all think?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 06, 2015, 12:28:33 pm
I appreciate that using a human to complete the NCVT circuit can be made reasonably safe. I believe I can grab a non-contact reference from the output side neutral feed before I power it up. Worst case I might have to plug a unit into the outlet strip for it to detect properly.

=======

Regarding testing for a ground-neutral swap this is less obvious but I am hatching a plan. Perhaps sniff the ground with a small audio amplifier that drives an ear bud or headphone... Clamp it so if you sniff the hot line it doesn't break anything, but I suspect listening to the neutral and ground with almost any product plugged into the same branch circuit should sound characteristically different.  If they sound exactly the same, they are obviously bootleg city.

This will need to grab an environmental ground to work so may require connecting to the human body to provide that audio ground reference. Don't try this at home with anything larger than a .04uF cap in series. Perhaps a little battery powered audio amp?

I need to think about this some more... no easy way to detect hot-neutral swap without taking apart the facility wiring (i.e. interrupt the ground at the panel and see which outlets stop working.  8) ).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 06, 2015, 05:56:39 pm
OK, have it buttoned up... wimpy ground wire and not a 300v Y cap but it's good enough for testing the concept.

3 pos switch so one way is hard ground, middle is ground lifted, and other side is 0.047 uF stinger cap.

I just had another interesting thought... If the cap in series with ground limits the current from a 120V fault to 3 mA and the GFCI doesn't trip until 6-7 mA a hot chassis fault will not trip the GFCI.  :o :o :o

Perhaps I need to resize the cap to current limit slightly above the GFCI trip current??

Every data point makes the picture clearer...  Now I will send this to an old friend who is a guitar guy and a design engineer for his first hand opinion. (I don't even have a grounded outlet in my house   :-[  or a guitar amp, or....) I am curious to learn if the .047 cap is quieter than floating the ground.. If I end up with .1uF or more the shielding should be even better.

JR.

PS: Speaking of grounded outlets, I just replaced my extremely tired dishwasher (pump making bad noises) and replaced the former 2 circuit romex power feed with a proper 3 wire line cord. Now both my 3 wire washing machine and 3 wire dishwasher plug into the same 2 wire outlet, in my laundry room. The outlet is literally about 6 feet from my fuse box (still using fuses). I am extremely tempted to drop a GFCI outlet into that box and run my own ground lead the several feet to pickup ground from a screw on the fuse box. Then I would finally have "one" grounded outlet in my house.  ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 06, 2015, 07:14:02 pm
I hope that 2 wire receptacle is GFCI protected-remember, NEC was changed as of 2014 to require GFCI protection for dishwashers.  The story I was told was that the manufacturers could not make the DW safe without GFCI protection.

I have always been OK with fuses-they are more failsafe than breakers, but in the last year I have come across two fuse boxes where the fiber insulating washers in the fuse holders had disintegrated.  Solves the issue of blown fuses, but makes me nervous about them.  Not sure when they quit making home fuse boxes-but they all seem to be getting some age on them these days.

The irony to not having grounded receptacles in your home yet is that in the last few years the actual need for them has diminished greatly-except in the laundry, kitchen and maybe at the computer desk. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Robert Lofgren on February 06, 2015, 08:49:10 pm
Robert, this is excellent. I've posted a pic of the relevant part of the manual in english. This appears to be a basic 3-light neon tester with an additional neon light connected between the ground contact and an external finger contact. We've discussed the use of a neon bulb for testing hot grounds, so this should work. Of course, this particular tester is for 230 volts only and won't fit an American "Edison" plug, but it should be possible to retrofit an extra neon bulb into a standard 3-light 120-volt Edison outlet tester. The real question is can this tester be UL listed since it could possibly expose the person performing the test to lethal current if the neon bulb and its current limiting resistor both shorted out. Yeah I don't think that double failure mode would be possible, but UL is funny about that sort of thing. What do you all think?
It is not an actual neon bulb that lights up. I only mentioned that the testing was similar to one. The square above the leds is a lcd that is activated by the PE-test.

It doesn't look like I can open it up without destroying it a little but give me a couple of days before I tear it apart  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 07, 2015, 12:49:28 pm
It is not an actual neon bulb that lights up. I only mentioned that the testing was similar to one. The square above the leds is a lcd that is activated by the PE-test.

It doesn't look like I can open it up without destroying it a little but give me a couple of days before I tear it apart  8)

So you think it's a NCVT built into a 3-light tester? I've been asking for that sort of thing for a long time.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 08, 2015, 01:02:01 pm
So you think it's a NCVT built into a 3-light tester? I've been asking for that sort of thing for a long time.

the internet ate my first answer so I'll keep this brief... I just added some neon bulbs to my current parts order. I suspect I can make a simple outlet checker with neon lamps and a touch contact that could detect reversed polarity, and open ground. But I need to build one to confirm... the neon lamps draw about 1 mA so should not be much of a shock hazard.

======
I am rethinking the value of the stinger cap with GFCI approach. The typical class A(?) GFCI is 5 mA +/-1 mA. I just confirmed on the bench that my stinger GFCI with only 0.1uF does not trip (4.5mA)... I am leaning toward 0.15 uF for enough current to trip the GFCI but still low enough that humans won't get stuck to it.  My parts vendor does not have any 0.15uF Y caps in stock, but they do make them.

Still evolving...

JR

PS: for more adventures in cheap house wiring, I just figure that if I convert my 2 wire outlet to three wire where both my washing machine and dishwasher plug in, a hot chassis fault in one will energize the chassis of the other.  :o :o So I definitely need to rig up a ground wire from the fuse box a few feet away.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 09, 2015, 03:41:44 am
the internet ate my first answer so I'll keep this brief... I just added some neon bulbs to my current parts order. I suspect I can make a simple outlet checker with neon lamps and a touch contact that could detect reversed polarity, and open ground. But I need to build one to confirm... the neon lamps draw about 1 mA so should not be much of a shock hazard.

======
I am rethinking the value of the stinger cap with GFCI approach. The typical class A(?) GFCI is 5 mA +/-1 mA. I just confirmed on the bench that my stinger GFCI with only 0.1uF does not trip (4.5mA)... I am leaning toward 0.15 uF for enough current to trip the GFCI but still low enough that humans won't get stuck to it.  My parts vendor does not have any 0.15uF Y caps in stock, but they do make them.

Still evolving...

JR

PS: for more adventures in cheap house wiring, I just figure that if I convert my 2 wire outlet to three wire where both my washing machine and dishwasher plug in, a hot chassis fault in one will energize the chassis of the other.  :o :o So I definitely need to rig up a ground wire from the fuse box a few feet away.   

Yes you can ... can't find the one I had; but FWIW I always ran something like this [below] in a spare socket in my racks and used RCD protection.  That's almost a manual version of what you are after.

Now we use this http://www.jands.com.au/brands/jands/power-distribution/PDS6RII
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 09, 2015, 09:42:42 am
Yes you can ... can't find the one I had; but FWIW I always ran something like this [below] in a spare socket in my racks and used RCD protection.  That's almost a manual version of what you are after.

Now we use this http://www.jands.com.au/brands/jands/power-distribution/PDS6RII
Does that tester catch RPBG?

Perhaps I wasn't clear... of course neon lamps can confirm power present, I am talking about using a simple neon lamp as a NCVT to probe neutral and ground for line voltage, by using the human body as the other contact for the bulb. A normal neon lamp draws less than 1 mA and even the high brightness that I found are something like 1.2mA so not much of a shock hazard, but I need to see if it works. Since the lamp will light at about 60V I could probably put enough of a resistor in series that even a shorted lamp would not make you stick to it (10-15 mA).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 09, 2015, 01:11:46 pm
I finished modifying my stinger GFCI test bed. I had to jury rig up a 0.15uF from 3 x 0.1uF but now I have 160V caps with enough current draw to trip the GFCI. Since I don't have a grounded outlet in my house I had to rig up a bootleg outlet to test it.. It appears I have reversed polarity on my workbench outlet, so I had to wire up the test outlet RPBG to get the bootleg ground on the neutral...   Testing a short to ground with the stinger cap in series with ground tripped the GFCI so now I feel like it is safe enough to continue testing.

6.7 mA is enough current to be felt as a shock but is well below the current that causes us to stick to it or experience serious injury...   

0.15uF should be even better at shielding than the typical .047 stinger cap used in old legacy amps. So I am pretty confident this will work.

Only difference is we should source some proper 0.15uF 300-400V Y caps. (The "y" rating insures that it will not fail as a short circuit for human safety on that application.)

JR

Note: if-when I make my electronic fuse that can trip much lower than the GFCI 4-6 mA I may add a path to trip the GFCI  open whenever the electronic fuse trips.
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on February 09, 2015, 03:32:20 pm
The misanthrope in me still thinks it more amusing to electrocute musicians.

/snark, satire, sarcasm, other literary devices

The last 2 weeks has taken me from curmudgeonliness to misanthropy - I'm learning to hate humanity one person at a time - and for some reason the persons of my disdain all seemed to have "musical" instruments in their hands.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 09, 2015, 05:26:41 pm
Perhaps you could convince JR to change the switch to a remote controlled switch and adding a 3rd position tied to a charged cap giving a charged similar to an electric fencer so a 3 pos switch-stinger cap * lifted ground * sting.  Might give a little satisfaction.  I know I don't feel real bad when, after putting the horses back in the pasture, I see their reaction when they test the fence.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 09, 2015, 05:41:41 pm
I'm not sure I should feed this veer... I'm trying to save musicians, but it's OK to see them jump and dance (St. Vitus) a little when they deserve to.  ;D

It seems a floating ground system at FOH, with a Van de Graf generator charging up the console chassis to thousands of volts, might do something. You may need to watch yourself when mixing but you could send some harmless voltage to the musician via mic ground. Of course you might blow up the console too...

JR

 
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on February 09, 2015, 06:38:06 pm
I'm not sure I should feed this veer... I'm trying to save musicians, but it's OK to see them jump and dance (St. Vitus) a little when they deserve to.  ;D

It seems a floating ground system at FOH, with a Van de Graf generator charging up the console chassis to thousands of volts, might do something. You may need to watch yourself when mixing but you could send some harmless voltage to the musician via mic ground. Of course you might blow up the console too...

JR

 

Yeah, there's a down side to the Van de Graf...

I'll continue to make sure our AC service is all tight and proper.  While it might be fun to watch the puppets dance, I don't want it to happen with our string...
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 09, 2015, 11:16:59 pm
I'm not sure I should feed this veer... I'm trying to save musicians, but it's OK to see them jump and dance (St. Vitus) a little when they deserve to.  ;D

It seems a floating ground system at FOH, with a Van de Graf generator charging up the console chassis to thousands of volts, might do something. You may need to watch yourself when mixing but you could send some harmless voltage to the musician via mic ground. Of course you might blow up the console too...

JR

 

Hi JR,

For some reason Van de Graf generator made me think of SIA at the Grammys. https://www.youtube.com/watch?v=jZEFuCxD7BE

She is actually from my home town and was in a band called Crisp(!) that I seem to remember providing production for …. Absolute talent!

...anyway regarding my above post, I think I was a little too cryptic.  My tester used neon’s with a resistor just as you described and the human body as the earth.

The picture I posted above is different, its a the 110 volt version I what I used with my rig. It would detect missing neutral, reverse polarity, no earth, and no power etc. Logically integrating these functions with an RCD will get you close for not many $$$
 
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 10, 2015, 02:52:13 am
oops double post
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 10, 2015, 01:34:08 pm

The picture I posted above is different, its a the 110 volt version I what I used with my rig. It would detect missing neutral, reverse polarity, no earth, and no power etc. Logically integrating these functions with an RCD will get you close for not many $$$

As Mike often points out this tester ASSUMES a correctly connected ground for polarity detection.  And the RPBG will show as a correctly wired receptacle-but still energize the chassis of any 3 wire plug and cord connected gear.  That is the dangerous-and most difficult to detect-condition JR is trying to prevent.





Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 10, 2015, 01:48:17 pm
As Mike often points out this tester ASSUMES a correctly connected ground for polarity detection.  And the RPBG will show as a correctly wired receptacle-but still energize the chassis of any 3 wire plug and cord connected gear.  That is the dangerous-and most difficult to detect-condition JR is trying to prevent.

I think the picture does not agree with the story... Peter has written that the tester grabs a reference from a human touching it. That indeed sounds like a NCVT and I suspect a simple NCVT could be made from neon lamps (I plan to order some and confirm that for myself).

That picture OTOH looks like one of the sundry crude outlet testers that ASSumes ground is 0V so can be tricked by bootleg wiring. In light of the number of reversed polarity outlets I've found in my house, I am very glad they didn't try to wire up grounded outlets by grabbing neutral.   :o :o

Maybe Peter can share a picture of the tester he is talking about, with the human reference contact. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 10, 2015, 02:49:11 pm
OK, have it buttoned up... wimpy ground wire and not a 300v Y cap but it's good enough for testing the concept.

3 pos switch so one way is hard ground, middle is ground lifted, and other side is 0.047 uF stinger cap.

<picture of an inline GFI with a toggle switch poking out of it>

Sorry, not going to work. It doesn't look like it's going to improve the sound. I know you don't want to color the sound, but in order to get accepted by the guitarist market, it at least has to look like it is going to "enhance" the sound in some way. A guitarist may not want to plug in anything that affects their sound, but they won't see the value in anything that doesn't.

Think audiophool (which I'm convinced many guitarists are, at heart, but without the cash to back it up). And looking like a plastic blob with a wart (toggle switch) poking out of it isn't going to win any awards in the "it looks like it'll sound great" department.

Maybe if you encase it in black marble and charge at least four figures.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 10, 2015, 03:43:07 pm
Sorry, not going to work. It doesn't look like it's going to improve the sound. I know you don't want to color the sound, but in order to get accepted by the guitarist market, it at least has to look like it is going to "enhance" the sound in some way. A guitarist may not want to plug in anything that affects their sound, but they won't see the value in anything that doesn't.
Never say never...  I just shipped it off to an old friend to do some real world testing.  I plugged a neighbor kids small peavey amp into it and I couldn't hear a difference in any of the three positions (as it should be). The guitar amp should be quiet wrt itself.

The friend of mine suggested that this might help with ground loops(?) While I am not sure what kind of ground loops you encounter at the front end of a guitar amp... Or maybe I should say I don't really want to know... If there are other grounds attached, that suggests that my cap ground lift is not really protective, but I'll deal with that when I learn more about his application

He mentioned input ground noise in connection with a high gain amp he is designing (same guy who designed the 5150 for Eddie Van Halen) so when he says high gain I believe him.  8)
Quote
Think audiophool (which I'm convinced many guitarists are, at heart, but without the cash to back it up). And looking like a plastic blob with a wart (toggle switch) poking out of it isn't going to win any awards in the "it looks like it'll sound great" department.
If I was serious about merchandising a premium versions of this I'd push the human safety angle for big name talent, or sound providers with a conscience. But I don't want to pay for some tort lawyers kid's college expenses so don't plan to sell these myself.  A simple Y cap, or perhaps a 7mA fuse ground mod to a commercial GFCI seems simple enough for DIY.
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Maybe if you encase it in black marble and charge at least four figures.

I never had the stomach to deal in snake lubricant. I was a value guy before there was such a thing. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 10, 2015, 03:48:02 pm
Maybe if you encase it in black marble and charge at least four figures.

In case you didn't figure it out, that entire post was intended to be sarcastic.  ;)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 10, 2015, 04:17:00 pm
In case you didn't figure it out, that entire post was intended to be sarcastic.  ;)

You may be kidding but the tone-sound quality thing is as serious as a heart attack. Musicians will play though dangerous legacy amps in pursuit of some elusive tone.

I trust my friend's ears to identify if there is any sound quality issue (he's an actual design engineer who designed guitar amps and now makes pedals). I was just going for "as good as" but he suggested it might actually be better.

We'll see. I'll be happy with "as good as".

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 10, 2015, 06:17:35 pm
I think the picture does not agree with the story... Peter has written that the tester grabs a reference from a human touching it. That indeed sounds like a NCVT and I suspect a simple NCVT could be made from neon lamps (I plan to order some and confirm that for myself).

That picture OTOH looks like one of the sundry crude outlet testers that ASSumes ground is 0V so can be tricked by bootleg wiring. In light of the number of reversed polarity outlets I've found in my house, I am very glad they didn't try to wire up grounded outlets by grabbing neutral.   :o :o

Maybe Peter can share a picture of the tester he is talking about, with the human reference contact. 

JR


The neon tester I mentioned was something I built as an apprentice. I think it was probably exactly what you have in mind.

FWIW although I have a lot of experience with electrical systems I have not in general participated in this thread because the electrical systems you have in the US are quite different from my experience.

We don’t have this problem. I have never seen or encountered a boot leg earth – never! We also don’t have bustard legs or whatever you call them where you centre tap one of your 3 phase delta windings and connect it to earth – 120V + 208V + 240 etc.

Everything is 3 phase star/delta. The earth is bonded to the neutral throughout the entire electricity distribution system and at every main switch board. RCD’s (GFCI) have been required for many years to be installed at the switch board so that the wiring throughout the building is also protected. 

…. anyway, I chose my words carefully, with respect to the power-point tester + GFCI comment and said “almost”  and “get you close”, i.e. not quite everything you need ;) ..still working on that  :-\
 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 10, 2015, 07:01:25 pm
My post was mainly meant for casual readers of this thread-seeing that picture followed by "detects reverse polarity" when dealing RPBG grounds could be hazardous.  These testers have their place-in a situation where multiple pieces of gear will be interconnected while being powered from different receptacles they are not really up to the task.

Neutral is bonded to earth here as well.  In your systems, do you have a neutral/earth and hot at each receptacle?  While we have various systems that can be confusing, bootleg grounding and reversed polarity are mainly the result of sloppy careless work or indifference.  Unfortunately, that indifference can be deadly. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 10, 2015, 09:41:46 pm
My post was mainly meant for casual readers of this thread-seeing that picture followed by "detects reverse polarity" when dealing RPBG grounds could be hazardous.  These testers have their place-in a situation where multiple pieces of gear will be interconnected while being powered from different receptacles they are not really up to the task.

Neutral is bonded to earth here as well.  In your systems, do you have a neutral/earth and hot at each receptacle?  While we have various systems that can be confusing, bootleg grounding and reversed polarity are mainly the result of sloppy careless work or indifference.  Unfortunately, that indifference can be deadly.

In Australia we always have an active, neutral and earth at all receptacles (GPO’s) including light fittings. In the passed an earth was not required for all light fittings. 

The issues for us in OZ, other than the condition of the wiring includes; no RCD protection, a reversed active & earth, or a poor neutral connection at the switch board or infrastructure level.  While I have never seen a boot-leg earth I believe very occasionally it does happen.

In addition all electrical work must be done by a licenced electrician and they are required by law to issue a certificate of electrical compliance for the work they do.

Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on February 11, 2015, 12:37:19 pm
If everything is from three phase and derived from the same generation source can you detect an inverted active neutral by phase?  Eg correctly wired will all be at 0deg, 120deg, 240deg while inverted wiring will be at another phase angle.

Doesn't help if they are all wired inverted.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 11, 2015, 12:52:18 pm
In Australia we always have an active, neutral and earth at all receptacles (GPO’s) including light fittings. In the passed an earth was not required for all light fittings. 

The issues for us in OZ, other than the condition of the wiring includes; no RCD protection, a reversed active & earth, or a poor neutral connection at the switch board or infrastructure level.  While I have never seen a boot-leg earth I believe very occasionally it does happen.

In addition all electrical work must be done by a licensed electrician and they are required by law to issue a certificate of electrical compliance for the work they do.

The problem in the USA is that electrical wiring is "grandfathered" and doesn't require an upgrade to code unless you're doing major renovation. So my 1923 house still has a lot of K&T (Knob & Tube) wiring which I'm replacing as we renovate each room. And there's a ton of Big Box stores (Home Depot and Lowes, etc...) that will sell anything to anybody, electrician or not. So anyone here can walk into a Home Depot store and buy a service panel, breakers, entrance wire, receptacles, GFCI's and anything else they like. And while local codes may requre a licensed electrician if there's going to be an inspection, most of time it's some DIY guy working on things with no formal training. And certainly, even licensed electricians make mistakes as well, even though they're supposed to know better. The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.     
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 11, 2015, 04:57:10 pm
If everything is from three phase and derived from the same generation source can you detect an inverted active neutral by phase?  Eg correctly wired will all be at 0deg, 120deg, 240deg while inverted wiring will be at another phase angle.

Doesn't help if they are all wired inverted.

If multiple phases are available, that is simply a voltage check-phase to phase V is always higher than phase to neutral.

Not only grandfathering is an issue, but up until about 10 years ago there were no licensing/inspection requirements in most of my service area.  I come across major code violations created by electricians that are of relatively recent install.  The inspection process is also a teaching process at times.

While we don't have "certificates of compliance", the permit (issued to the contractor responsible) along with an inspectors approval serves as the same legally.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 11, 2015, 07:04:19 pm
The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.   

Hence, things like "stinger caps," non-polarized plugs, and the general reason for this thread. If everything that's not double-insulated was in fact grounded, and grounded according to modern electrical standards, there would be almost no need for this thread. But it's not. So we're left with finding a way to make something that's inherently unsafe, safe. Without modifying the tone.
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 11, 2015, 10:14:30 pm
The problem in the USA is that electrical wiring is "grandfathered" and doesn't require an upgrade to code unless you're doing major renovation. So my 1923 house still has a lot of K&T (Knob & Tube) wiring which I'm replacing as we renovate each room. And there's a ton of Big Box stores (Home Depot and Lowes, etc...) that will sell anything to anybody, electrician or not. So anyone here can walk into a Home Depot store and buy a service panel, breakers, entrance wire, receptacles, GFCI's and anything else they like. And while local codes may requre a licensed electrician if there's going to be an inspection, most of time it's some DIY guy working on things with no formal training. And certainly, even licensed electricians make mistakes as well, even though they're supposed to know better. The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.   

Its similar in Australia – existing wiring can remain but all new wiring and modifications need to be done to the new / current standards. There can often be a knock on effect and a small addition can cause a major switchboard upgrade.

It’s generally not possible to get a new or reconnected supply from the network unless an electrician has signed off that the installation is safe.
Wiring standards are also reasonably consistent across the whole country.

You can also buy DIY parts, but most people use electricians.  I suspect the additional dangers associated with 230V as opposed to 110V may have something to do with it; 230 volts tends not to be very forgiving.
Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 13, 2015, 02:09:25 am
OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.

Title: Re: brain storm an optimal human safety system for back line
Post by: Peter Morris on February 13, 2015, 05:13:09 am
OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.



Cheap version  $$$$ , but not complete protection - delete (2)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 13, 2015, 09:50:30 am
OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.

I like the concept...  8)  It might confuse some people if it doesn't turn on when they try while wearing gloves.

A charged up capacitor could keep it turned on during brief power outages, but not very long. I'd need to think about unintended consequences if an already on power drop gets unplugged and then plugged into a different outlet without properly vetting that second outlet. 

The safest way is to require manual resetting.  If you give users a way to cheat a safety system, they will...

 
JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on February 13, 2015, 11:16:46 am

The safest way is to require manual resetting.  If you give users a way to cheat a safety system, they will...

JR
True that. :(
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 17, 2015, 01:23:10 pm
Well my modified GFCI outlet drop is sitting in my friends shop, but he is slammed with NAMM orders and a recent ice storm so has been too busy to check it out yet.

I'm glad to see somebody in the MI business doing so well (go James). 

++++++++

I have given more thought to Peter's idea, and using the touch switch to turn on triacs sensing the difference between the (hot) line and environmental ground would in effect confirm that the line is actually hot, so neutral by definition can not be hot. This does not protect against ground being hot but it seems less likely.

The stinger cap in series with ground still seems like the ultimate solution and why complicate this with extra sense circuits? KISS just modify a standard GFCI if my friend's noise floor testing of the stinger cap approach proves satisfactory. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 07, 2015, 10:16:32 am
Got my parts in...  ;D

Since I still have my modified GFCI out on loan for testing, I need to build another GFCI + relay into a junction box. I have one GFCI outlet laying around I can use.

I need to experiment some with the ground current detector... I need to light up the LED input side of an opto-isolator with 1.2V or so... A few hundred ohm resistor in series with the ground lead should generate enough voltage to fire the opto (output imbalanced the GFCI) with only a few mA leakage in the ground lead.

I can use a few neon lamps to indicate 1- On power available/or off tripped 2- a neon lamp from input side neutral to output side neutral could light up is reverse polarity "and" GFCI tripped.

So the smart outlet will not automatically disconnect from RPBG drop, until it senses a few mA of current in the ground lead.

I guess I could add another opto-isolator between the input side neutral (that should be 0V) and output side neutral but I don't know if there is enough current there to trip the GFCI. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 08, 2015, 02:35:13 pm
Yesterday I bought a cheap neon lamp tester at Wally World for $2.95... Works like I remember and it is UL/CSA approved (category 2, 300v max).  When connected across 120VAC it draws 250uA which is consistent with 100k series resistance and 95V lamp breakdown voltage.

Testing my loose neon lamps that just showed up the same measurement indicates 500uA so more like 70V lamp breakdown.

I can light the neon lamps one at time by touching the free lead (just like the tester), but when the lamps are connected together they work differently than I thought.   Two neon lamps in series with 120V across the pair do not light at all, that is not unexpected but what was, if I grab the junction of the two lamps, both light up??? If I add diodes neither one lights up (the rectified AC probably charges my body capacitor up to 150V DC just like static charges do).

Interesting I only measure 2 uA of current from me grabbing the neon lamp with my hand so hard to see in direct light.

Based on this preliminary testing I still like the $3 neon lamp tester to parse out hot leads in an outlet, but I could already do that with my VOM.

MO later...

   JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on March 08, 2015, 05:25:13 pm

I can light the neon lamps one at time by touching the free lead (just like the tester), but when the lamps are connected together they work differently than I thought.   Two neon lamps in series with 120V across the pair do not light at all, that is not unexpected but what was, if I grab the junction of the two lamps, both light up??? If I add diodes neither one lights up (the rectified AC probably charges my body capacitor up to 150V DC just like static charges do).


My first thought is that when 2 lamps are in series they see roughly 60 vac across each-below strike voltage.  When you touch the junction, the lamp connected to the hot lead sees 120 VAC so it lights, but then its maintaining voltage is lower so it allows the 2nd lamp to see a high enough voltage to strike?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 09, 2015, 11:45:27 am
My first thought is that when 2 lamps are in series they see roughly 60 vac across each-below strike voltage.  When you touch the junction, the lamp connected to the hot lead sees 120 VAC so it lights, but then its maintaining voltage is lower so it allows the 2nd lamp to see a high enough voltage to strike?

It's always interesting when we get an unexpected result, forcing us to learn something or stay confused.

To explore or model what was going on I experimented with applying real capacitors from the junction of the neon lamps to neutral.

exp #1 .001uF cap... the line lamp glows steadily with ocassional flashes from neutral lamp.
exp #2 240 pF cap    both lamps remain dark.
exp #3 470 pF cap    both lamps glow similar to human body.

So I look approximately like a 470 pF cap... (IIRC from googling this the human body is more like 100-300pF ).

Yes, I guess we have an obscure scenario where first the line lamp fires, charging up the small cap until the voltage across that lamp is too low to sustain it, but by then there is enough voltage to fire the neutral lamp.

With too low C this never fires to get started. (the high brightness lamps I bought are 95V min... normal brightness lamps fire at 65V). The 1000pF is enough that the neutral doesn't fire, or just blinks randomly, and 470 pF is like Goldilock's porridge, just right to light both. An odd coincidence that the human capacitance falls in the sweet spot range for this obscure mechanism***.

The bad news is that none of this helps me by itself. and reinforces that I need to buffer myself to look like a larger capacitance or lower Z... With lower Z I would get the proper Line lamp lit.  I now have parts (400V mosfets) so I can make the buffer. I suspect with the buffer I can use daylight bright LEDs and operate at lower impedance so ghost currents are ignored. The neon lamps can glow with as little as single digit microamps but very dimly. Of course I need to build this to confirm there are no more surprises.

I'm pretty sure the world doesn't need a $20 outlet checker when the $3 neon lamp appears to work adequately for general testing. FWIW I just probed the floating ground pin on my kitchen GFCI outlet and the neon lamp glows, so this is not definitive and susceptible to ghost voltages/currents. Note: I already replaced my old electric kettle that was the worst offender for leaking current to ground, but floating grounds will likely report hot in other real systems too. So maybe the world does need a better outlet tester.   

JR

*** circuit designers are often haunted by marginally stable circuits that only work when you touch a component , or more insious when you put a scope probe on it (pF of capacitance). With high impedance design, sometimes your touch provides a DC path, but more often it's the capacitance. I have heard horror stories of military R&D projects where a finished prototype shipped with a scope probe inside hanging off the circuit node that made it work. No doubt to meet a date deadline.   :o :o (No I would never do that.).   
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 12, 2015, 01:45:09 pm
Another update, I finished breadboarding my "touch" buffer using a pair of P and N power mosfets. Unfortunately it doesn't work as I hoped. I'm pretty sure the outlet on my bench is reversed polarity with floating ground, so for my first trial my buffer power supply is swinging 120V AC with 160V dc rails above and below that AC.

It is hard to put a scope probe on this but my suspicion is that the power mosfets I used have a few hundred pF of input capacitance each, so that swamps out my bodies puny couple hundred pF. So back to the drawing board, I haven't failed, I just proved another way that doesn't work.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 14, 2015, 07:36:02 pm
I don't want to count my chickens before they hatch but my second alternate approach appears to work (so far)... It requires a separate touch probe for each line being tested, but on my bench I can now reliably detect and indicate correct or reversed polarity power. I didn't breadboard up a ground probe but for a RPBG that ground will scan the same as any other hot lead so that should work.

I need to buy some different parts,,, I no longer need the 400V parts, I can drop down to 200V and just enough current to light a LED so the 300pF mosfet input capacitance can drop to <100 pF.  Not sure if this will help or hurt..

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on March 16, 2015, 04:14:42 pm
I don't want to count my chickens before they hatch but my second alternate approach appears to work (so far)... It requires a separate touch probe for each line being tested, but on my bench I can now reliably detect and indicate correct or reversed polarity power. I didn't breadboard up a ground probe but for a RPBG that ground will scan the same as any other hot lead so that should work.

I need to buy some different parts,,, I no longer need the 400V parts, I can drop down to 200V and just enough current to light a LED so the 300pF mosfet input capacitance can drop to <100 pF.  Not sure if this will help or hurt..

JR

JR, I have already determined that using 3 neon lamps with a common touch pad has too many unpredictable interaction, so I'm also cooking up a version with 3 separate touch pads driving three separate neon lamps. One thought was a touch pad with insulated concentric circles to let fingertip resistance isolate the circuits a bit, but in my head I don't think it will work. This probably needs 3 separate touch pads for proper isolation. The problem seems to be that some unterminated lines will still have leakage current due to capacitive or inductive or some other "ive" effect. Since this needs to sniff out any condition, that could be a design killer. My 6-light tester may need a set of 3 tungsten bulbs for the original 3-light tester part, and 3 neon lamps for the "hot line to earth" test.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 16, 2015, 06:12:03 pm
JR, I have already determined that using 3 neon lamps with a common touch pad has too many unpredictable interaction, so I'm also cooking up a version with 3 separate touch pads driving three separate neon lamps.
+1 to 3 separate touch contacts (great minds think alike).  8)
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One thought was a touch pad with insulated concentric circles to let fingertip resistance isolate the circuits a bit, but in my head I don't think it will work. This probably needs 3 separate touch pads for proper isolation.
At high impedances the finger resistance could short them together... With my approach that could serve as a lamp test (all three would light up). 
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The problem seems to be that some unterminated lines will still have leakage current due to capacitive or inductive or some other "ive" effect. Since this needs to sniff out any condition, that could be a design killer. My 6-light tester may need a set of 3 tungsten bulbs for the original 3-light tester part, and 3 neon lamps for the "hot line to earth" test.

One concern I am trying to address is phantom voltages that the neon lamps can report as positive results too (like my kitchen outlet grounds that are floating).

JR

PS: I need to order new parts to reduce my input capacitance (a factor of 3)... This project is testing my understanding of the physical world around us. Not only are we a resistance and capacitance to some vague environmental ground, we are also an antenna/voltage source (I estimate a few volts near my bench). A 1Meg shunt is enough to damp this human noise voltage. Verrry interesting...
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on March 16, 2015, 11:49:13 pm

PS: I need to order new parts to reduce my input capacitance (a factor of 3)... This project is testing my understanding of the physical world around us. Not only are we a resistance and capacitance to some vague environmental ground, we are also an antenna/voltage source (I estimate a few volts near my bench). A 1Meg shunt is enough to damp this human noise voltage. Verrry interesting...

I wish more of the younger generation would enjoy the discovery process.

Is high impedance necessary?  What if you lower the impedance with say 30-40k resistors connected in a y -hot to neutral, hot-ground, and neutral-ground?

Also, since you were using a common touch pad, I am guessing the neons were connected line (to be tested)-ballast resistor-neon-touchpad.  What if you changed to line (to be tested)-neon-ballast resistor-touchpad?  That would isolate the neons to some degree? 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 17, 2015, 09:38:55 am
I wish more of the younger generation would enjoy the discovery process.
I am always happy to learn new stuff...
Quote
Is high impedance necessary?  What if you lower the impedance with say 30-40k resistors connected in a y -hot to neutral, hot-ground, and neutral-ground?
The problem is impedance to what...? Impedance between line and neutral is not a problem but between a floating ground and whatever will just weakly bond ground to that voltage. An impedance to both will raise a floating ground to V/2.

My mosfet buffers allow me to use lower impedance LED indicators on the output side, while hopefully providing a repeatable input sense contact.. That still needs to be proved. My first design was too complex and didn't work.. It is getting simpler and mostly working which is a good sign.   
Quote
Also, since you were using a common touch pad, I am guessing the neons were connected line (to be tested)-ballast resistor-neon-touchpad.  What if you changed to line (to be tested)-neon-ballast resistor-touchpad?  That would isolate the neons to some degree?

If I understand your question it's no difference for series components to change their order.

JR

PS: Another thing I am hooping for with increased sensitivity is to use a non-human stand-in for the environmental ground reference. I did not get an indication from an open line cord, but touching the plug from my electric drill worked. On reflection the drill was probably sitting on my carpet while I performed that test which might have affected it's ability to mimic a ground reference. Ideally I'd like to be able to sense hot/cold without touching meat.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on March 17, 2015, 12:11:26 pm
If you place a relatively low impedance from a floating ground to neutral that should bleed off any phantom voltage-just like a low impedance VOM.  At least that is my thinking.

Yes, series components all have same current flow, and oder does not change that-but this is not a simple series circuit. If the neon lamps are connected to a touchpad they are interfering with each other.  Placing the ballast between the neon and the touchpad puts that impedance between the lamps so you get 2 times the ballast isolation-similar too, but more predictable than using three separate touchpads connected by your skin.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 17, 2015, 12:19:29 pm
If you place a relatively low impedance from a floating ground to neutral that should bleed off any phantom voltage-just like a low impedance VOM.  At least that is my thinking.
Yes, but if the line and neutral polarity are unknown, you may be connecting ground to hot.

One test involving micro control switches a load between hot and ground, then looks to see if neutral and ground show similar artifacts. I am not enthusiastic about making one of these and think a simpler way might be possible with an audio sniffer (just listen to ground and neutral.. they should sound subtly different when neutral is under load. )
Quote

Yes, series components all have same current flow, and oder does not change that-but this is not a simple series circuit. If the neon lamps are connected to a touchpad they are interfering with each other.  Placing the ballast between the neon and the touchpad puts that impedance between the lamps so you get 2 times the ballast isolation-similar too, but more predictable than using three separate touchpads connected by your skin.

Sorry I still don't see much difference...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 30, 2015, 10:21:56 am
Good news, I finally heard back from my serious guitar tester....To refresh everyone's memory since it has been a while, I modified a GFCI outlet strip with a 3 pos switch so the ground could be selected between, hard ground, open circuit, or cap coupled (my proverbial stinger cap throwback).  I used a 0.15uF cap to insure it would draw enough current from a fault to trip the GFCI (6 mA).

My tester was a guitar amp design engineer, who now runs his own company designing and selling guitar pedals (amptweaker). It took him so long to get around to testing this for me, because his business has been slammed with orders (just signed two new distributors overseas at NAMM show).

Long story short, the ground in "cap" position was identical for noise floor to the hard grounded position. An additional benefit that I didn't anticipate is that the cap position is quieter than the hard grounded position, if there is a ground loop (wrong name for what is going on) created by amp plugged into one branch circuit and pedals plugged into a different outlet (in another room).

He tested it with a very high gain amp (James designed the EVH 5150 while at Peavey so he knows high gain) and under typical use scenarios. 

So I am now satisfied that the GFCI + cap is a viable approach for back line. My main stipulation is that the ground cap be a "Y" cap (tested to not fail as a short). I was able to source some 0.1uF Y caps but no 0.15 yet. The larger cap is needed to insure the GDFI will trip if the fault path is through that ground cap.

JR

PS: I am kicking around a modification to the GFCI circuit that senses for current (or voltage) in the cap coupled ground path to trip the GFCI at less than 6 mA in that ground. 
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on March 31, 2015, 12:04:26 am
Good news, I finally heard back from my serious guitar tester....To refresh everyone's memory since it has been a while, I modified a GFCI outlet strip with a 3 pos switch so the ground could be selected between, hard ground, open circuit, or cap coupled (my proverbial stinger cap throwback).  I used a 0.15uF cap to insure it would draw enough current from a fault to trip the GFCI (6 mA).

My tester was a guitar amp design engineer, who now runs his own company designing and selling guitar pedals (amptweaker). It took him so long to get around to testing this for me, because his business has been slammed with orders (just signed two new distributors overseas at NAMM show).

Long story short, the ground in "cap" position was identical for noise floor to the hard grounded position. An additional benefit that I didn't anticipate is that the cap position is quieter than the hard grounded position, if there is a ground loop (wrong name for what is going on) created by amp plugged into one branch circuit and pedals plugged into a different outlet (in another room).

He tested it with a very high gain amp (James designed the EVH 5150 while at Peavey so he knows high gain) and under typical use scenarios. 

So I am now satisfied that the GFCI + cap is a viable approach for back line. My main stipulation is that the ground cap be a "Y" cap (tested to not fail as a short). I was able to source some 0.1uF Y caps but no 0.15 yet. The larger cap is needed to insure the GDFI will trip if the fault path is through that ground cap.

JR

PS: I am kicking around a modification to the GFCI circuit that senses for current (or voltage) in the cap coupled ground path to trip the GFCI at less than 6 mA in that ground.
Cool beans!  Good test.  I like the added benefit of the quieting the "ground loop" misnomer. 
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 09, 2015, 12:22:51 pm
I am about ready to stick a fork in this KISS version... A GFCI power drop with "Y" cap in series with ground. My testing has satisfied me that this would provide another degree of human safety for back line use, while providing the additional benefit in reducing "ground loop" noise issues. Besides that probably not being an accurate description for what is causing the ground related hum, if a pedal or preamp in front of the protected guitar amp is plugged into a different grounded power outlet (or why would there be hum), that other ground is not cap isolated so again a shock hazard from rouge external mains voltage faults.

I believe there is merit in somebody (not me) making and selling a GFCI power drop with stinger cap. While this might finesse UL requirements by labeling the ground differently, it would be really nice for UL to bless this, or at least not discourage it.

=========

Part deux is the smart GFCI drop and this would have enhanced features beyond the KISS version. An additional power disconnect relay could test for RPBG and never power up, if outlet wiring is rogue. Further it could sense for voltage/current in the ground path and use that to trip the GFCI and/or disconnect power/ground relay.

Perhaps this could even measure mains voltage and not turn on if voltage too high (or too low).

I DO NOT BELIEVE THIS IS A SELLABLE PRODUCT.... musicians are not suitably motivated by human safety to pay what this would cost... and it would probably come with some liability if people still manage to get hurt.

The KISS version has a much better chance of commercial success and seem hard to screw up.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 24, 2015, 08:30:33 pm
I've finished my side project so I'm back on this for now.

I am reluctant to put a microprocessor inside because debugging a hot chassis design could be shocking. 

To build upon the KISS (tm) GFCI power drop, I have another enhancement-work around to protect the ground.

I am uncomfortable with making the ground carry 6mA to trip the GFCI and leaving it always connected even after a fault.  My improved approach uses a 3 pole relay to disconnect Line, Neutral, and ground after a fault. The relay goes in series with the GFCI and mains power. The relay coil is powered from the output side of the GFCI. The relay is momentarily bypassed to latch the system on, and once the GFCI comes up the relay is powered and supplies continuous power to the GFCI. If there is a fault and the CFCI opens, the relay opens too, opening up the ground.

Now I can improve the sensitivity of ground current and use a fault detected there to imbalance the GFCI and trip it off.

I have other possible enhancement to pursue, but this should allow us to increase the sensitivity of ground fault currents and open up that path completely.

Of course the devil is in the details, but I'm soaking this idea in beer right now.... I'm optimistic.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on April 24, 2015, 11:17:19 pm
Since commercial GFCIs disconnect both hot and neutral when they trip, in theory you could use a SPDT relay to connect the ground-disconnecting the ground if the GFCI is tripped.  Using a second GFCI with adjustable sensitivity in in series to monitor current on the EGC would complete the protection.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on April 26, 2015, 08:42:06 am
Of course the devil is in the details, but I'm soaking this idea in beer right now.... I'm optimistic.  8)

Per your recommendation I soaked this in beer last night, and came up with a slightly different spin. Rather than creating a bunch of extra circuitry to disconnect the EGC feeding the stinger cap, why not just add a neon bulb with its own series resistor in parallel with the stinger cap? That way, if there was a hot ground for whatever reason (RPBG, line-to-chassis fault, etc...), and touched the guitar strings, the neon bulb would light up indicating a "hot ground".

So by adding just three parts to a standard GFCI receptacle (Stinger cap, neon bulb, 100K ballast resistor) you would not only protect musicians from a hot guitar or hot mic, you would add an extra indicator light that told them what to look for when troubleshooting why the GFCI tripped.

Hey, it was really good beer... ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 26, 2015, 10:41:35 am
Per your recommendation I soaked this in beer last night, and came up with a slightly different spin. Rather than creating a bunch of extra circuitry to disconnect the EGC feeding the stinger cap, why not just add a neon bulb with its own series resistor in parallel with the stinger cap. That way, if there was a hot ground for whatever reason (RPBG, line-to-chassis fault, etc...), and touched the guitar strings, the neon bulb would light up indicating a "hot ground".
Nice, but I bet the musician can probably feel the 6mA or so. :o  While more lights are always good.  ;D


Quote
So by adding three parts to a standard GFCI receptacle (Stinger cap, neon bulb, 100K ballast resistor) you would not only protect musicians from a hot guitar or hot mic, you would add an extra indicator light that told them what to look for when troubleshooting why the GFCI tripped.

Hey, it was really good beer... ;D
With the KISS(tm) approach or KISS+Neon, the hot ground does not automatically trip the GFCI, so for RPBG the stinger cap coupled ground is still connected. It will only draw 6 mA through the ground cap if hard path to ground exists (like muso holding mic and guitar strings.) Six mA is not life threatening and safe as is, while not very pleasant.

KISS+Relay in minimum complexity configuration is relay with coil powered from output side of GFCI so ground path is also lifted whenever GFCI trips. I am not sure that this adds benefit commensurate with cost.

KISS+Relay+smart glue.  My goal, is to add some extra logic to enhance the GFCI trip modes. Sensing the voltage/current in the ground path, and when above some arbitrary threshold trip the GFCI, which removes power from the relay so opens up the ground. This way adds detection and protection against a different fault vector hopefully with even more sensitivity than the GFCI's 5mA +/-1mA.

In addition to adding a disconnect on ground fault, I can add some more glue logic, to turn on the relay (with one or two relay poles supplying mains power to the GFCI when on to latch the circuit powered up. The jump start power to turn on the GFCI + relay is switched via a touch switch that only works if the outlet Line lead is hot. This way if Line and Neutral leads are reversed (like in a RPBG), the unit will not latch power on when the on switch is touched.  Neon bulbs can be added for various passive indication. A neon lamp across the relay ground pole could indicate voltage present input/output ground. Another neon lamp could confirm that miswired outlet has voltage present, just not the correct polarity if power switch is unresponsive.

I need to do some testing, but i suspect I might be able to operate the touch switch automatically from the output side of the GFCI (neutral) with products plugged into the strip. Even better if the GFCI and power drop output side had enough capacitance to provide the low reference to turn it on. Having to re-latch the power strip if power is interrupted may be undesirable.

JR   

PS: I need to be careful that my intentional imbalance of the GFCI when it detects ground current does not accidentally correct an imbalance in the GFCI especially if that is the original source of the ground current. IMO this is unlikely but something to anticipate. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim Padrick on April 26, 2015, 02:06:57 pm
Design it.

Patent it.

Sell it to Whirlwind to add to their extensive line of power goodies.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 26, 2015, 04:15:54 pm
Design it.
already in process
Quote
Patent it.
Not worth the time and $5-10k. All a patent does is give you the right to sue... and you can still lose in court after you sue (ask me how I know that  >:( ).
Quote
Sell it to Whirlwind to add to their extensive line of power goodies.
My work effort in this is published (here) and free for anybody to use. To do this right for production somebody has to invest several $k into establishing a UL file to test and prove that the concept is solid, while i have no doubt.

I don't see a huge commercial market for this. The external or secondary hot ground seems to be a music industry specific problem mostly affecting live performers. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on April 27, 2015, 06:16:39 am
All a patent does is give you the right to sue
And it lets your competitors know what you are planning.


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on April 27, 2015, 09:38:21 am
And it lets your competitors know what you are planning.

I remember when I worked for Corning Glass many moons ago that the patent on Corelle glass was getting ready to expire, and Anchor Hocking (a big competitor) was posed to market something similar. AH had built a new factory and had the glass making process up and running a year in advance, so on the very day the Corning held patent expired, Anchor Hocking had magazine ads out promoting their own version, and they were shipping product.   

That's why there are so many trade secrets rather than patents.
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on April 27, 2015, 10:28:18 am
And why a good patent won't show how to make something.  In fact, it doesn't even need to work at the time of taking out the patent as all you are patenting is an idea.


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 27, 2015, 10:46:32 am
I remember when I worked for Corning Glass many moons ago that the patent on Corelle glass was getting ready to expire, and Anchor Hocking (a big competitor) was posed to market something similar. AH had built a new factory and had the glass making process up and running a year in advance, so on the very day the Corning held patent expired, Anchor Hocking had magazine ads out promoting their own version, and they were shipping product.   

That's why there are so many trade secrets rather than patents.
With nine patents under my belt (the majority work for hire at Peavey) I have no regrets about a patent that runs it's course and expires. That's some 15-20 years to make hay, and come up with another good idea.

When I designed my first automatic mixer at Peavey, Dan Dugan's patent was about to expire, so my choices were to come up with some work-around to not infringe, or wait a little to use the proven algorithm. (I did get granted a patent for an improved AM feature.).

The big drug companies work to extend patent protection, by re-inventing their own drugs with patentable variants, hoping to keep perpetual patent protection.   

While I was at Peavey I would try to talk Hartley out of filing international patents on some of my inventions because the cost vs protection was not very good, not to mention how long it would take. Some of Peavey's japanese patents, issued after the product had already be replaced with a newer model.

I have also had negative experiences where my most valuable patent at Peavey was copied. They even got their own patent for a variation. When Peavey sued them, Peavey was not able to stop them or win any compensation. So the patent and expensive lawsuit was a waste of time and money.  >:(

I have also seen abuses where small companies get put out business by only slightly larger companies with a weak patent but strong lawyers, that the weaker company can not defend against. I almost got involved in one case as in interested third party, but decided to not poke the litigious bear as a weak company myself..  (It cost real money to challenge patents in court, and the results are not always straightforward.)

JR

@Steve.. The patent office routinely disallows patents for perpetual motion machines and the like, while i suspect some obscure cutting edge technologies are harder to vet. Not only must a patent work but by law the inventor is supposed to reveal the preferred embodiment (best way). I have read many patents where the embodiment published is far from practical, but most look like they should work. There is a bit of gamesmanship regarding preferred embodiment, and I've never seen a patent overturned for publishing a less than optimal circuit, as long as it works. The claims language often confounds even me, and I've been reading these for decades. The claims are written in english, but it's another version of english where words take on powerful new meanings. I wrote most of my own last patent, but I paid a real lawyer real money to write the claims section because they matter that much.   
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on April 27, 2015, 10:52:59 am
@Steve.. The patent office routinely disallows patents for perpetual motion machines and the like, while i suspect some obscure cutting edge technologies are harder to vet.

Perhaps I worded that incorrectly.  At work, we have patented things which we know will work but we haven't yet worked out the manufacturing process.
A patent needs to be as vague as you can get away with as it will cover any uses you haven't thought of yet - whereas if it is very specific, someone else might have that same alternative use idea and get round your patent.


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 27, 2015, 11:14:28 am

Perhaps I worded that incorrectly.  At work, we have patented things which we know will work but we haven't yet worked out the manufacturing process.
A patent needs to be as vague as you can get away with as it will cover any uses you haven't thought of yet - whereas if it is very specific, someone else might have that same alternative use idea and get round your patent.


Steve.

Yes... there is gamesmanship about how much to reveal (as little as you can get away with***). Sometimes the value of a patent is in how cheap and easy the implementation is. I got one patent for adding a diode clipper across the bass boost leg of Baxandall tone control. It was impossible to conceal that best practice. There was only one way to do that, and no way was that not documented in the patent.

I have invested some hindsight into my (Peavey's) unsuccessful patent defense, and am not completely clear on the law. I thought variant (called improvement) patents give the 2nd inventor the right to use the improvement, but does not remove the responsibility to honor the base patent holder. In fact improvement patents are well know strategy practiced by big companies hoping to trade improvement patents in return for access to the original patent. Of course I am not a lawyer and was not directly involved in Peavey's unsuccessful defense, other than write an affidavit about my invention and talk with their "expert" EE witness on the phone, once. I was not impressed by the expert, so I guess I shouldn't be surprised by the outcome. If I was still working at Peavey I would have personally involved myself into the case, (I could play the expert) but this court case happened years after I quit Peavey so that was not an option. I had to read the court filings on the WWW like everybody else.

JR

[edit] *** it is worth noting that the spirit of the patent system is to publish the invention so others skilled in the art can use it to increase their knowledge and build upon that science to invent other stuff. In exchange for sharing that knowledge the inventor gets exclusive use for a limited time. 

From where I sit the patent system seems to be in disarray with abuses all over the place, but i don't see easy answers as fixes often incur unintended consequences. One supposed fix, to make it easier to challenge bad patents has been abused by stock market short sellers to short a company with a proposed "bad" patent and then cheaply challenge the patent. Wether they win or not, the stock will drop in the short term and they can profit from that.  [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on April 27, 2015, 01:25:11 pm
I have also seen abuses where small companies get put out business by only slightly larger companies with a weak patent but strong lawyers, that the weaker company can not defend against. I almost got involved in one case as in interested third party, but decided to not poke the litigious bear as a weak company myself..  (It cost real money to challenge patents in court, and the results are not always straightforward.)

Whether patent-related or otherwise, the power of the lawsuit is sometimes used to punish another party even if the other party's defense is solid. For some small companies and individuals with a clear defense where they most likely would win the lawsuit, or even if they DO win the lawsuit, the cost of defense is more than they can bear. Many times they just roll over and settle out of court because it's cheaper. The suing party wins whether they "win" or "lose" the case.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 04, 2015, 02:51:05 pm
We'll now to veer back on topic...

This weekend I discovered more parts I need to buy. The first relays I bought for this project were only 1 pole so not going to get it done. And apparently I blew up all of my 16a triacs on another project. :-(

So plan looks like 3 pole relay that disconnects power "and" ground from input of power drop. Coil for relay is powered from output side of GFCI so when GFCI trips the relay opens and stay open until GFCI is reset.

[/edit]
arghh.. just pulled the trigger on another $50+ parts order.. relays in small quantity $15 each... I need to get a cheaper hobby. 
[edit]

Start up circuit will use a touch sensor to switch on a triac to jump start the GFCI (in parallel with relay line pole) only if the line input is actually hot.... Once the relay closes the relay will supply power to the GFCI unit. If the outlet wiring is reverse polarity and the line is actually neutral, this circuit will never start up.

TBD with some bench work is if I can do this start up automatically. When the relay is open I can use the output side ground or neutral as a substitute for the touch probe (ASSuming there is enough capacitance to environmental ground, and/or my touch circuit is sensitive enough). This way the GFCI will automatically power up when power is applied. In my last touch sensor I could get it indicate from touching a power drill line cord, so this "could" work. I expect ny next touch circuit to be even more sensitive than that one.

If nothing is plugged into the power drop a finger touch might be required, but if nothing is plugged in it doesn't need to work. :-)

I plan to add a secondary sensor to detect voltage/current in the ground path and trip the GFCI unit if it detects a fault there. So far my best approach shows a worst case sensitivity around 5 mA, so not much better than the GFCI sensitivity , but this will protect against an external voltage/current source feeding the ground independent of the GFCI legs.

If the outlet has an open ground this floating ground will not draw any current so not trip the GFCI by itself. I might add a third circuit where I look for voltage on a floating ground say relative to input neutral and use that to trip the GFCI to remove power.

Neon lamps can provide indication of sundry status metrics.

I still don't feel this is very marketable, but I want to build at least one I can send to Mike to put through it's paces.

JR

PS: Thinking about this more, I think UL might consider different rules for SKUs that have the potential for being operated in the vicinity of multiple mains power branches. Guitar amps and consoles would fit this category. Rather than asking for input grounds to be bonded to carry tens of amps, maybe current limit them with stinger caps. This could be incorporated inside new guitar amps and the like, cheaper than adding external sense and disconnect circuitry.

PPS: Yesterday in my kitchen I felt and measured 109V @ 375uA between my mixer and the wood counter's metal trim strip. I can imagine the mixer leaking some current since the outlet isn't grounded but i didn't expect the wood counter to be such a good conductor to earth. Still more than a factor of ten below my GFCI trip point. :-(
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on May 04, 2015, 03:55:54 pm
PPS: Yesterday in my kitchen I felt and measured 109V @ 375uA between my mixer and the wood counter's metal trim strip. I can imagine the mixer leaking some current since the outlet isn't grounded but i didn't expect the wood counter to be such a good conductor to earth. Still more than a factor of ten below my GFCI trip point. :-(

Yeah, damp wood is a pretty good conductor, and all my POCO guys warn me about loggers cutting down trees that contact 11KV power lines and electrocute themselves. They say to leave your chain saw and run away... run away fast. Then call the power company and let them deal with it.

 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 05, 2015, 11:54:40 am
Yeah, damp wood is a pretty good conductor, and all my POCO guys warn me about loggers cutting down trees that contact 11KV power lines and electrocute themselves. They say to leave your chain saw and run away... run away fast. Then call the power company and let them deal with it.
[veer]
The wood inside my kitchen counter tops hasn't been green for half a century. I still do not understand where the resistance path between the counter trim and metal sink is but I measure about 100k there. Just for chuckles I measured capacitance and got around 0.4 nF. (Perhaps 50 years of smutz under the counter.)

My (food) mixer measures 1.2 nF between one leg of the line cord and ground. This capacitance is asymmetrical, only .2 nF on other leg, so outlet polarity could matter for conducted leakage.

I really need to re-wire my house with grounded outlet wiring but that's way too much work...   [/veer]

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on May 05, 2015, 11:19:33 pm
[veer]
The wood inside my kitchen counter tops hasn't been green for half a century. I still do not understand where the resistance path between the counter trim and metal sink is but I measure about 100k there. Just for chuckles I measured capacitance and got around 0.4 nF. (Perhaps 50 years of smutz under the counter.)

My (food) mixer measures 1.2 nF between one leg of the line cord and ground. This capacitance is asymmetrical, only .2 nF on other leg, so outlet polarity could matter for conducted leakage.

I really need to re-wire my house with grounded outlet wiring but that's way too much work...   [/veer]

JR

Since you bust on American English what is smutz?  Is that a collection of old porn?  Shmutz is yiddish slang for anything messy.  IE:  I got shmutz on my shirt.  It can also be used as a verb IE: I shmutzed up the tablecloth.  Short for shmutzik that is dirt.

Don't get me wrong I am not all fershlugina over this.  Fershtay?

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 06, 2015, 10:09:45 am
Since you bust on American English what is smutz?  Is that a collection of old porn?  Shmutz is yiddish slang for anything messy.  IE:  I got shmutz on my shirt.  It can also be used as a verb IE: I shmutzed up the tablecloth.  Short for shmutzik that is dirt.

Don't get me wrong I am not all fershlugina over this.  Fershtay?

Yes I meant shmutz but I don't spell yiddish or english very well. I was referring to food debris and dirt that gets trapped around the cracks and edges of counter edge and top surfaces... I'm sure there is decades of shmutz trapped behind the metal trim.

I suspect shmutz could be somewhat conductive due to moisture content.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on May 06, 2015, 09:53:01 pm
and I was just being silly sitting on the couch recovering from a dental appointment that started with "do you really need nova Caine I am running behind" explaining that since I already had a root canal it would hurt. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on May 06, 2015, 10:06:58 pm
and I was just being silly sitting on the couch recovering from a dental appointment that started with "do you really need nova Caine I am running behind" explaining that since I already had a root canal it would hurt.

A former colleague told me of a trip to the dentist - the patient was in the chair and the doc said "open, please".  The patient reached back, grasped the dentist's scrotum and asked "Doc, we're not going to hurt each other, are we?"
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 06, 2015, 10:15:10 pm
and I was just being silly sitting on the couch recovering from a dental appointment that started with "do you really need nova Caine I am running behind" explaining that since I already had a root canal it would hurt.
wouldn't (?)

The root canal has removed the damaged nerve tissue from the tooth. Root canals are not fun. In theory no nerve means no pain. But it seems it always hurts some. If not during the dental visit, later when you get the bill. 

JR   
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on May 06, 2015, 11:05:05 pm
wouldn't (?)

The root canal has removed the damaged nerve tissue from the tooth. Root canals are not fun. In theory no nerve means no pain. But it seems it always hurts some. If not during the dental visit, later when you get the bill. 

JR

To veer this back on topic (sort of), the most awful pain you can experience without actual injury is when the dentist tags a nerve with the needle and you feel a full-body neural electrical overload. What I would've given to have a GFCI in my nervous system...

Talk about a "brain storm." I'd call it about a 12 on the pain scale... a scale which only goes to 10.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on May 07, 2015, 08:22:57 am
To veer this back on topic (sort of), the most awful pain you can experience without actual injury is when the dentist tags a nerve with the needle and you feel a full-body neural electrical overload. What I would've given to have a GFCI in my nervous system...

You can get a smaller version of this by chomping down on a ball of aluminum foil. I think there's some battery action going on between the dissimilar metals of your fillings and the aluminum, with your saliva serving as the electrolyte. But it's been a long time since I tried that. 

OK... Back OT. I'm pretty sure you can't fit a GFCI in your teeth.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 19, 2015, 08:41:21 pm
OK, back in topic... I finally started melting solder on this project.

Bad news first, I figured out that my preliminary design was short several parts. To make it ignore reverse polarity outlets, I needed to use triac switches on both the line and neutral inputs .... OK 2 triacs, and 2 opto drivers. I got the touch switch working but need to tweak the sensitivity... right now it turns on for both correct polarity and reverse polarity too (not good).

The good news is the relay coil powered from the output side of the GFCI latches on, from the touch switch momentary power,  and opens power and ground if the GFCI opens.

Tomorrow I will start tweaking on the touch switch sensitivity. It needs to only work for correct polarity power or there is no need for it.

So good progress...so far, but more bench work to go. 

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 20, 2015, 01:23:48 pm
More progress... It turns out I had a bench issue. I know that my bench power is both ungrounded and reverse polarity. I rigged up a loose outlet as an adapter with bootleg ground, to test GFCI before. Apparently I didn't reverse the polarity in this adapter so what I thought was correct polarity, was still reverse polarity in both test modes.

Now I am getting correct operation from my touch switch.. i.e. touch contact turns on and latches the GFCI outlet on for correct polarity wired outlet. If outlet is reverse polarity touch switch does not work. It will occasionally still trigger from the touch circuit with reverse polarity, perhaps once every 25 touches or so,  but I can probably harden for that. 

So far I have proved out a smart GFCI that refuses to turn on for miswired outlet, "and" opens the ground when GFCI trips. Already pretty cool, but more to go.

Remaining to be tested is can I add a secondary GFCI trip circuit from measuring voltage/current flowing in the ground and use that to trip the GFCI and open the ground path too.  I plan to use the same opto-osolator I am using for the triacs. worst case 5 mA for rated output, but I expect it to work at even lower trip current. Note: this ground current threshold is separate from and independent of the GFCI. I intentionally imbalance the GFCI to force it to trip when I sense current in the ground that could be coming from anywhere.

JR

PS: I tested using the not yet powered up output side of the GFCI as an alternate touch input to hopefully turn on the outlet automatically when power is applied but it works too well... turning on for reverse polarity too. I may soak this in beer and revisit this later. I don't care for having to reset this every time power blinks off.   


Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on May 20, 2015, 01:52:19 pm
I think it more humane for music and art to simply let the AC flow.... and if some numb-nuts muso wants to run dangerous equipment that results in his death or injury, that's his personal decision.  Kind of the libertarian approach to safety...  /satire, sort of but not really

Tim "still cynical after all these years" Mc
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on May 21, 2015, 10:01:47 am
Tim's got a point-JR is expending a lot of brain power and energy primarily because other's don't wanna use theirs-but it seems like JR is enjoying this(or maybe he just wants an excuse to barricade himself in his basement?)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 21, 2015, 11:49:14 am
It is never good business to allow the talent to get hurt even when it isn't our fault. I have seen examples of this and the lawyers will often stretch to blame anyone even peripherally involved if they look like they have deep pockets. (Look at all the sound equipment they own. ) 

=======

Back on topic. I connected the ground current sense and it trips the GFCI with no ground fault but only at start-up. If I re-connect my opto-shunt after it is started and latched, it doesn't trip the GFCI so that's what I need to fix today. There is something weird about the initial start-up conditions causing this.

My opto-triac has 400V of safe off voltage and only tens of nA leakage when off, so that should not trip the GFCI, and doesn't trip it after it is on and stable. Perhaps some capacitance not shown on the data sheet? (This is why we breadboard circuits.  8) )

JR

PS: Yes this is an exercise in mental masturbation. I will never manufacture these and frankly there aren't that many actual deaths specifically caused by this fault (while likely more than global warming). This is just a pet cause of mine and we have the technology to prevent death for 99.9%. In fact GFCI with stinger cap does that already. I plan to publish full schematics after I get it working.
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on May 21, 2015, 12:50:36 pm
It is never good business to allow the talent to get hurt even when it isn't our fault. I have seen examples of this and the lawyers will often stretch to blame anyone even peripherally involved if they look like they have deep pockets. (Look at all the sound equipment they own. ) 

=======

Back on topic. I connected the ground current sense and it trips the GFCI with no ground fault but only at start-up. If I re-connect my opto-shunt after it is started and latched, it doesn't trip the GFCI so that's what I need to fix today. There is something weird about the initial start-up conditions causing this.

My opto-triac has 400V of safe off voltage and only tens of nA leakage when off, so that should not trip the GFCI, and doesn't trip it after it is on and stable. Perhaps some capacitance not shown on the data sheet? (This is why we breadboard circuits.  8) )

JR

PS: Yes this is an exercise in mental masturbation. I will never manufacture these and frankly there aren't that many actual deaths specifically caused by this fault (while likely more than global warming). This is just a pet cause of mine and we have the technology to prevent death for 99.9%. In fact GFCI with stinger cap does that already. I plan to publish full schematics after I get it working.

Don't get me wrong - I'm not about people dying because of someone elses bad/unsafe decisions - but if some stupid twit thinks that using his precious vintage electrocution device is more important than his personal safety, WHO AM I to tell him no by using a device that interrupts power?  I'm being partly sarcastic and absolutely serious at the same time...

I believe it's our responsibility to provide stage power that is up to Code and meets or exceeds all generally recognized safe practices.  It's not our job to tell "An ARTISTE" that his stuff sucks and he can't use it on our stage because someone got electrocuted 5 years ago or on another continent.  Can you imagine the lawsuit from the promoter and ticket buyers when "ZXY sound company refused to provide power" and the show is cancelled in the ARTISTE's fit of pique?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 21, 2015, 01:11:20 pm
Don't get me wrong - I'm not about people dying because of someone elses bad/unsafe decisions - but if some stupid twit thinks that using his precious vintage electrocution device is more important than his personal safety, WHO AM I to tell him no by using a device that interrupts power?  I'm being partly sarcastic and absolutely serious at the same time...
Natural selection will always be in play. I saw a recent post where a GFCI was patched around due to unexplained tripping. In my judgement it is worse to bypass a safety device, than not use one in the first place. That said the "show must go on" mentality usually wins in the short term.
Quote
I believe it's our responsibility to provide stage power that is up to Code and meets or exceeds all generally recognized safe practices.  It's not our job to tell "An ARTISTE" that his stuff sucks and he can't use it on our stage because someone got electrocuted 5 years ago or on another continent.  Can you imagine the lawsuit from the promoter and ticket buyers when "ZXY sound company refused to provide power" and the show is cancelled in the ARTISTE's fit of pique?
As compared to said ARTISTE being killed? Choose your poison. I posted about liability issues, but there is also a strong component of just doing what is right.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on May 21, 2015, 01:49:47 pm
Natural selection will always be in play. I saw a recent post where a GFCI was patched around due to unexplained tripping. In my judgement it is worse to bypass a safety device, than not use one in the first place. That said the "show must go on" mentality usually wins in the short term. As compared to said ARTISTE being killed? Choose your poison. I posted about liability issues, but there is also a strong component of just doing what is right.

JR

Some ARTISTEs would rather die than play a safer rig or at a lower volume or... or... make ANY change whatsoever.  In any confrontational aspect of artistic relations, the production company will be voted off the island.  Can you tell I've been down this road recently?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 21, 2015, 02:13:20 pm
OK back on topic, I just got the ground sense circuit working. I had to increase the series resistance in my shunt circuit from GFCI output line-hot, to GFCI input neutral, to intentionally trip the GFCI. according to spec this only needs to be 6mA max, but I worry if there are multiple faults going on at the same time. Right now my shunt is delivering 8 mA nominal so should work even with low line and high tolerance GFCI.

My initial speculation was that the shunt opto-triac had enough terminal to terminal capacitance when off to trip the GFCI. The GFCI sensitivity may be different during start up too. Another data point is that the opto-triac has something like an up to 1000V/uSec rise time limit... So thyrister probably conducts if hit with really really fast edge rates. Perhaps an added C across the triac working with the series R could slow it down enough to not turn on.. but that C would conduct current too.  :o  arghh another trapeze act. Making the shunt R larger probably already forms a RC with the intrinsic triac body capacitance (pF?) . Add a cap to slow it down below 1000V/usec but don't sink so much current it trips the GFCI.    8)


JR


Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 21, 2015, 02:20:26 pm
Some ARTISTEs would rather die than play a safer rig or at a lower volume or... or... make ANY change whatsoever.  In any confrontational aspect of artistic relations, the production company will be voted off the island.  Can you tell I've been down this road recently?
Even a lowly musician probably doesn't really want to be killed by his amp, while I can appreciate being loyal to a legacy amp tone.

My simple cheap and dirty GFCI with stinger cap, has been tested to actually be quieter than a hard grounded outlet for some pedal applications, and never noisier or negatively affecting tone.

The GFCI will protect an unwashed musician from his faulty amp, and the stinger cap will protect against the hot mic scenario.

If the musician really needs killin, don't do it on stage in front of witnesses.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on May 21, 2015, 04:31:35 pm
<snip>

If the musician really needs killin, don't do it on stage in front of witnesses.

JR

Yeah, unless the lampie is in on the deal and can pull off the complete blackout and restore trick (as done in the murder mystery shows).
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on May 21, 2015, 11:56:14 pm
I think it more humane for music and art to simply let the AC flow.... and if some numb-nuts muso wants to run dangerous equipment that results in his death or injury, that's his personal decision.  Kind of the libertarian approach to safety...  /satire, sort of but not really

Tim "still cynical after all these years" Mc

Thin the heard
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 22, 2015, 03:32:44 pm
I will try to ignore the dark humor this thread has engendered and I appreciate many of you are bored. I would be bored too if i wasn't still learning.

The last squirrely part was the GFCI tripping during start up... It appears that this is in fact related to the edge rate of the initial waveform  (apparently more than 1000V/uSec ). One of the reasons I take this much time to refine the design is because I have my over-night team of design engineers (my sub-concious) always working at solving difficult design problems in the back ground. 

To restate the problem If I added a RxC across the shunt load, the current drawn by the cap would contribute to tripping the GFCI. Making the shunt resistor larger was a POOGE (not a real fix). The fix that my overnight team came up with, and shared with me yesterday while i was out riding my bike, is to connect the C of the RC shunt to the output side neutral, so at start up the RxC current is all in the output side circuit and does not imbalance the GFCI. When the circuitry senses ground current and turns on the opto-triac, it connects the output resistor to the input side neutral... It now works like a charm (with .01uF cap) and I have returned to my original value R so I can be confident that my ground trip does not interfere with a marginal GFCI fault at low current.

Once this trips the 3 pole relay opens up and nobody will be at risk from this outlet.  8)

To be determined still is optimum ground current sense circuit, but i no longer need to worry about keeping max ground current under 12mA so you can't get stuck to it... since it will open circuit almost immediately getting stuck is not a concern.

Finally...

PS: After i clean this up, I will send the working proto along to Mike to double check my work on his bench that simulates sundry power faults. My bench is a little dicey, with an RPBG wired outlet on purpose to reverse polarity back correct again, and provide a ground path, so I can test the ground current trip...  I don't have a real grounded outlet in my whole house.
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on May 22, 2015, 04:35:11 pm
I *have* been following along, John, and your sharing the design evolution is genuinely appreciated.  Even though I'm not playing along at home (like I suspect a couple readers are) I think you're giving a wonderful lesson on what is needed to develop an idea into a concept, and that concept into a prototype.  That's cool.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 22, 2015, 09:47:31 pm
Now that I got the ground shunt triac sorted, I went back and revisited my auto-start or auto-restart feature.

I configured the power relay, so that when the relay is powered down, the output side neutral is available to use as an alternate turn-on touch input.

If nothing is plugged into the the GFCI outlet it will not auto start, but with my electric drill plugged in, the capacitance of the line cord and drill is enough to start up and latch the power relay.

In use with a guitar amp plugged in, a momentary power outage should just restart it when power is restored.

I will still provide the touch start terminal. Now with my low capacitance mosfet the input resistor in series is 1M, so 120V is only 120 uA or <1/8th  of a mA. Even I don't feel that.

JR

PS Thanks Tim et al...
 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 24, 2015, 06:27:14 pm
here is schematic and a proper description. Note: incorrect symbol for opto-triacs but it didn't feel like creating a new symbol.

The basic premise is to start with a standard GFCI outlet that protects against leakage from it's hot that doesn't find it's way back to it's return. BUT this does not protect musicians from the classic hot mic problem. If the mic is hot because the console ground is hot a standard GFCI will not protect the muso. If the GFCI is plugged into a RPBG outlet the properly grounded mic can still be deadly.  :o

The 3 pole relay not only removes power but also releases the ground. The relay coil is powered from the GFCI output so anytime the GFCI trips, ground is lifted too. An additional circuit senses for current flowing in the ground, and when more than a few mA is detected an opto-triac creates and artificial leakage fault in the GFCI to trip it.

i had some fun figuring out why the shunt opto-triac was tripping the GFCI at start-up. Apparently there is a 1000V/uSec voltage rise time limit, which start-up apparently exceeded, causing the opto-triac to conduct, and trip the GFCI. by adding a C from the shunt R to output side neutral I am able to slow down the edge rate of that voltage, while the RC current in completely in the output side so looks like valid current flow to the GFCI.

In addition to protecting against improper power to the console (mic). Another problem is RPBG outlets. When converting 2-circuit wiring to 3-circuit outlets some people "bootleg" the ground by shorting it to neutral. This is wrong for multiple reasons, but even worse if the line and neutral are reversed, so the bootleg ground instead of grabbing neutral, is now hot. As I have posted before people have been killed by these RPBG (reverse polarity bootleg ground) outlets. My solution to protect against RPBG, is to use a touch switch start up circuit that only works if line and neutral are wired correct polarity.

I accomplish this touch switch start-up using a high impedance MOSFET device with it's source connected to the (hot) line circuit. A small (.1uF) reservoir cap and diode from neutral charges up this floating DC power. Since the MOSFET is swinging at 120VAC, connecting the touch contact to anything near 0V will turn on the MOSFET drawing current through the two opto-triac LEDs, which in turn turns on two 16A triacs to apply power to the GFCI. (two TRIACs are needed to prevent issues from RPBG), Once the GFCI is powered up, the relay coil winding connected to the GFCI output turns on the relay and latches power on.

One downside to requiring a touch switch input to turn on could be momentary power outages causing power to stay off until reset again. This is not cool since power can blink in the middle of a performance and you don't want to have to hunt around to reset power. My design fix for this is to provide an alternate touch input that when the power relay is open, senses the output side neutral. As long as some equipment is plugged into the GFCI outlet, this will probably be enough to automatically reset and latch the relay back on. With my prototype an empty outlet stays off, but plugging as small hand drill into the outlet is enough of an environmental 0V reference to reset power when restored.

This is not very cheap... In small quantity the GFCI outlet was $15, the 3-pole relay another $15... the 2x 16A triacs and 3x opto-triacs were maybe $1 each... the small MOSFET was relatively inexpensive.

I will provide an accurate BOM for any who ask.

JR

PS: This touch switch technology is unlike anything that I have seen in my research. Most touch switches use either finger DCR to complete an electrical circuit between two external contacts, Another touch switch uses capacitance to shift the frequency or rise time of some AC signal. A third uses two sandwiched electrical overlays where finger pressure completes an electrical circuit. My approach basically assumes the free standing human body is sitting at a low modest AC voltage, especially relative to the mains 120V. The high impedance MOSFET will turn on from as little as 1V AC so a direct comparison between the human body and either line or neutral would turn on. I had to reduce the sensitivity so that it would ignore a direct comparison to neutral, like for a reversed outlet wiring situation. I pad down the 1M input R into a 240k R so the voltage difference is reduced to 1/5th actual. In a really noisy environment a noisy human might turn on a reverse wired outlet, but the ground sense currect circuit will still protect the talent.

PPS: For another data point when I probe my line voltage using a relatively high impedance VOM, using my body as the low reference, I measure around 50VAC on the 120VAC hot line, but I also measure 10VAC on the cold neutral line. I am not sure how exactly to interpret this. Probing other outlets around my house found neutral readings as low as <1V but I suspect I am really reading my body voltage
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on May 24, 2015, 10:54:51 pm
Looks like a job well done-its too bad that getting a UL listing would multiply the development cost many many times.

I understand the situation-as an electrician, I spend a lot of time trying to keep people who don't seem to care from hurting themselves or destroying property.  Without code mandates, it would be really hard to convince a lot of people to install GFCIs-and many other things we do.

Unfortunately, code mandates is likely what it would take to make this product commercially viable.  However,I doubt the statistics would ever flag this as an item worthy of a code mandate-and even if it did happen some would bristle at the mandates.

Hopefully some will see the value and build one for their own protection.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 24, 2015, 11:46:48 pm
My own judgement is that this is over-designed.. the KISS approach with a stinger cap in series with the ground leg, of a stock GFCI, provides adequate protection against all faults and may not need UL listing at all if properly labelled. (No EGC).

A UL file is probably $10k or more to open, and I doubt there is much market for these. I just wanted to see if I could, and in looks like I could.  8)

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on May 25, 2015, 12:00:40 am
JR, I'm trying to picture what the externals of your device looks like, but my imagination is either not good enough, or maybe it is too good. Besides GFCI devices that are box-mounted, I have also seen in-line devices. (I've seen in-line devices with pigtails, and other with molded 5-15 ends.). I'm not sure what the touch switch would look like, however.

Would you give me (us) an idea of what form your device has?  Thanks!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 25, 2015, 12:31:41 am
http://forums.prosoundweb.com/index.php/topic,152668.msg1406346.html#msg1406346 (http://forums.prosoundweb.com/index.php/topic,152668.msg1406346.html#msg1406346)Here's a picture of a prototype I did of the KISS version built into a commercial power drop (ignore the extra switch, that was for testing).

The 16A relay is almost as big as the GFCI outlet but this proto fits inside a standard two outlet box.

The touch switch may not even be necessary, since it will start up as long as a piece of equipment is plugged in.

For the prototype I may connect the touch contact to a face plate screw (it's a plastic box so no grounded to worry about.)

I mainly see this as like an specialized power strip for muso's to use for back line. Especially for singing guitar players.

 JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on May 25, 2015, 03:46:29 pm
Thank you. I must have seen that picture, but I didn't recall seeing it.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on May 25, 2015, 09:23:29 pm
My own judgement is that this is over-designed.. the KISS approach with a stinger cap in series with the ground leg, of a stock GFCI, provides adequate protection against all faults and may not need UL listing at all if properly labelled. (No EGC).

Yes, I would agree that a stinger cap and a stock GFCI should provide sufficient protection against any failure mechanism I can think of. I know you're interested in disconnecting the EGC and thus stopping the fault current from a hot mic back through the GFIC's ground. But I think that current limiting that to the few mA that the stinger cap will pass is good enough. That should be sufficient to wake up the musician without injuring him/her, and in that scenario won't cause the GFCI to trip. I've never met a musician who appreciated having their backline power go off during a set.

So take your standard GFCI/stinger-cap circuit and just add a neon bulb with current limiting resistor in parallel with the stinger cap. That adds an indicator light that you could put a "Hot Mic" sticker on which would provide some actual troubleshooting intel in addition to saving their life. Let's call this the KISS+ device.

Could this KISS+ device be produced without getting specific UL approval? I don't know myself, but I do know somebody who might, and they're watching this thread. Could it be manufactured cheaply enough that musicians or sound techs would buy it? I think if it doesn't require a huge investment in UL testing and could be built/sold in reasonable quantities, maybe. I'm sure that JR knows a lot more about manufacturing than I do. I'm more of an industrial/calibration guy, but I do know a little about manufacturing scaling and costs.   
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 26, 2015, 10:21:00 am
Yes, I would agree that a stinger cap and a stock GFCI should provide sufficient protection against any failure mechanism I can think of. I know you're interested in disconnecting the EGC and thus stopping the fault current from a hot mic back through the GFIC's ground. But I think that current limiting that to the few mA that the stinger cap will pass is good enough. That should be sufficient to wake up the musician without injuring him/her, and in that scenario won't cause the GFCI to trip. I've never met a musician who appreciated having their backline power go off during a set.
True
Quote
So take your standard GFCI/stinger-cap circuit and just add a neon bulb with current limiting resistor in parallel with the stinger cap. That adds an indicator light that you could put a "Hot Mic" sticker on which would provide some actual troubleshooting intel in addition to saving their life. Let's call this the KISS+ device.
Maybe just label it "Danger".
Quote
Could this KISS+ device be produced without getting specific UL approval? I don't know myself, but I do know somebody who might, and they're watching this thread. Could it be manufactured cheaply enough that musicians or sound techs would buy it? I think if it doesn't require a huge investment in UL testing and could be built/sold in reasonable quantities, maybe. I'm sure that JR knows a lot more about manufacturing than I do. I'm more of an industrial/calibration guy, but I do know a little about manufacturing scaling and costs.
It will be incrementally more expensive than the standard GFCI outlet strip that is already considered pricy by most musicians.  Replacing a pass through ground wire with a suitable "Y" cap (IMO it needs to be large enough to trip the GFCI from a line to ground fault) should cost maybe $1 more in decent volume, but this market will not generate decent volume so a $25 power strop could cost $50+.

I have identified one company that makes GFCI strips but haven't been able to talk with their product guys (yet). 

JR

PS: This +relay design is perhaps more of interest for being able to recognize reverse polarity outlet wiring. Maybe I should think about a dedicated tester. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on May 26, 2015, 04:46:00 pm
Yes, I would agree that a stinger cap and a stock GFCI should provide sufficient protection against any failure mechanism I can think of.
 

You are probably right with this statement.  Its the electrician side of me (especially when I spend a significant portion of my time dealing with 480) that feels a whole lot better with that air gap that I can see! 

What about a third party aftermarket modification of an existing power strip?  The quantities you are talking likely could be done by hand-and simply adding the correct cap could be done in 5-10 minutes tops if the correct power strip design was chosen to start with and a little practice.  You could teach someone to do it almost as quickly, a plug in test jig to verify and away you go.   Still no UL listing of course.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on May 27, 2015, 12:10:32 pm
You are probably right with this statement.  Its the electrician side of me (especially when I spend a significant portion of my time dealing with 480) that feels a whole lot better with that air gap that I can see! 

What about a third party aftermarket modification of an existing power strip?  The quantities you are talking likely could be done by hand-and simply adding the correct cap could be done in 5-10 minutes tops if the correct power strip design was chosen to start with and a little practice.  You could teach someone to do it almost as quickly, a plug in test jig to verify and away you go.   Still no UL listing of course.

IIRC you don't need a UL listing to sell a power strip, unless you're selling them to labs, government facilities and offices that REQUIRE UL listed gear. I've done this exact sort of thing a few times in the past where I modified a power strip with reversed back-to-back zener diodes to make a 5-volt ground loop lifter. Yikes!!!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 27, 2015, 01:03:04 pm
IIRC you don't need a UL listing to sell a power strip, unless you're selling them to labs, government facilities and offices that REQUIRE UL listed gear. I've done this exact sort of thing a few times in the past where I modified a power strip with reversed back-to-back zener diodes to make a 5-volt ground loop lifter. Yikes!!!
Yes, BUT.... If you ever end up in court being sued by the family of a dead muso, having UL sitting at your table in court as the expert witness is useful. Better than them testifying against you.

While i am not enthusiastic about spending $10k (or whatever to open a file) IMO it is worth dotting the I's and crossing the T's.

Back in my Peavey days I'd just ask the in house guy to ask them... I may have to do that myself.

JR
 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 09, 2015, 03:06:35 pm
I submitted a question to UL via their website about the stinger GFCI and no response... I'm shocked.

=========

I mentioned in passing that I am working on an outlet tester with a single touch contact.

I have 3 of the 4 colored LED indications working... I'll give more details after I get the 4th going.

JR

PS: First thing i'm going to do with this is test all my outlets.
Title: Re: brain storm an optimal human safety system for back line
Post by: Don Boomer on June 09, 2015, 06:53:44 pm

Back in my Peavey days I'd just ask the in house guy to ask them.

Do you suppose they have one anymore  ;) ;) ;)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 09, 2015, 07:37:30 pm
Do you suppose they have one anymore  ;) ;) ;)
I've been gone from there longer than you... you tell me.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 10, 2015, 01:48:52 pm
Update ... Time to stick a fork in rev two... another fail. The three sense LEDs work to detect hot outlet contacts but they only flash momentarily when the touch contact is touched. I can make it light steady with 3 separate touch contacts but that is too awkward and IMO unreliable.

I already have a new strategy for rev 3...

This is pretty interesting design territory for me... I can't even use my scope to see what's going on because the scope needs to be grounded and it's 1-10 megOhm input impedance would affect the circuits.

I did use this tester as is to test the outlets in my house and as expected none were grounded, and most (not all) were correct polarity.

More later... I need to melt more solder on rev 3.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 13, 2015, 12:04:27 am
Update...  rev 3 is disappointing..

I may fall back to using 3 separate touch contacts.

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 14, 2015, 11:25:06 am
Update...  rev 3 is disappointing..

I may fall back to using 3 separate touch contacts.

JR

JR... All of the experiments and schematics I've played with suggest that the cross-talk from a single contact would be problematic. So 3 separate touch contacts is probably the correct path.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 14, 2015, 02:13:10 pm
JR... All of the experiments and schematics I've played with suggest that the cross-talk from a single contact would be problematic. So 3 separate touch contacts is probably the correct path.

Thanks... designing an accurate outlet checker is proving a bunch harder than most such circuits, and I am fairly well versed in discrete design.

Yes, I know 3 separate touch circuits will work (I'm pretty sure) based on the same circuit I used as a start-up switch for my smart outlet.

When (if) I give up on making a single touch contact work, that 3 separate contacts approach will be my fall back position.

Last night during my nightly beer fueled circuit analysis session I resolved that I gave up too soon on version 3, so today I will revisit that with a few minor changes. Rev 3 was almost working.

more later...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 14, 2015, 05:41:06 pm
ATTENTION... my beer powered analysis was absolutely correct, proving once again that the only sure-fire way to fail is to give up.  :o

While not ready for prime time I now have my one touch outlet checker working on my bench.  8) I have a little bit of leakage between the LEDs but it seems pretty clear what is being indicated.

To repeat I have 4 LEDS;

A green "ground connection present" that lights for both real grounds and bootleg grounds (even RPBG) so it doesn't tell you about the quality of the ground only if ground path is conductive or not.

A second green LED lights if you touch the touch contact and the outlet Line terminal is hot. (I tested this on several outlets around my house and this works).

A yellow LED lights if the Neutral is hot to suggest caution. Most product will work fine with line and neutral reversed.  The outlet powering my bench is neutral hot and this tested as expected.

A red LED (Danger Will Robinson) lights up if ground is hot, like if the outlet is wired RPBG.. Actually both the yellow and red LEDs light up for RPBG. I had to intentionally rig up a RPBG outlet adapter to prove this.

I get a little leakage in the off LEDs and will look at fine tuning the individual LED currents. My very old (from the '70s) LEDs are not as efficient as modern LEDs so the old red is probably 10x the efficiency of the old yellow and 2x the old green. That and the fact that my neutral doesn't seem to be 0V may contribute to some ghosting. Testing outlets with my VOM on AC Volts scale with my body serving as the ground, I measure 45VAC on the line and about 10VAC on neutral. At least at my bench, some other outlets around the house have less VAC on neutral measured that way, but the difference is probably my body's reference voltage which will be different depending on where I am standing/sitting.

Long story short it works... The good news is this version uses less parts too.. only one MOSFET with all 3 LEDs connected to the one FET. When I am not touching the probe, the source of the MOSFET is high impedance and swings all over. When I touch the probe which connects the high impedance MOSFET gate to my body's reference voltage, the MOSFET source becomes a low impedance and sources current to the LEDs, the LED with AC voltage on the other end of it lights up.

I'll scratch out a schematic for those following along at home but the values will not be completely final yet.

This could be a very tiny SMD PCB that could probably fit inside a conventional outlet tester.... or almost anything.

 ;D ;D ;D ;D ;D

JR
 

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 14, 2015, 10:40:41 pm
Here is a schematic but like i said subject to change.

Looks simple after it's done.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 15, 2015, 11:32:47 am
To explain how this works for any still following along, the MOSFET is configured as a high impedance source follower to buffer the human reference voltage, so the touch probe sees very low current (maybe 100uA max).

The three outlet terminals that we want to test all connect to the source of T4 through 10k current limit resistors and rectifier steering diodes, so they only conduct during the negative half cycle of mains voltage. Generally only one of those three terminals will have AC voltage on it, except for RPBG where two will be hot. The drain of the MOSFET connects through diodes to both Line and Neutral so it will always be able to pull power from the one that isn't hot (and negative when the LEDs are lighting). When one of the three LEDs is on and drawing current the MOSFET drain will be pulling current from the actual neutral through one of those two diodes.

When not touching the touch contact, the gate will be swinging 120VAC and the MOSFET will be off. When touched it will be roughly 0V (give or take). That MOSFET will turn on enough to light the LEDs with a few 1/10s of a volt so source will be < 1V below the DC voltage of the human capacitor. Since the MOSFET source is a low impedance the hot outlet terminal LED will light up to indicate wiring status.

One problem I experienced before was that the MOSFET gate drive would suck current from the human capacitor so the LEDs would only flash momentarily then go out. The 100k pull up resistor in parallel with the MOSFET recharges the human capacitor. I may experiment with making that 100k larger, maybe 1M. With 100k some very efficient LEDs might start to glow when not touching the probe, while that might be OK to indicate power present and LEDs working.

The zener diode and 1M connected from gate to source of the MOSFET protects the MOSFET from too high gate voltage, and turns it off quickly when touch is removed. The MOSFET can tolerate +/- 20V gate to source drive so I could just use a smaller resistor at R8 to divide down the max gate voltage to <20V but then the source voltage would sag too much when turned on and LEDs wouldn't get as much drive voltage.

The ground present LED is a simple LED and current limit resistor from ground to either Line or Neutral via diodes. This is crude and will indicate ground present for bootleg and even RPBG grounds. A true ground quality test is far more complicated. 

This would be a very tiny SMD PCB... it could probably fit inside a standard plug, or maybe build it into a KISS stinger GFCI outlet strip. Perhaps might fit in an outlet cover plate.

JR

(http://forums.prosoundweb.com/index.php?action=dlattach;topic=152668.0;attach=14017;image)
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on June 15, 2015, 02:33:07 pm
John, you've really done some fine work on this.  Now go build something to keep you in hops.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 16, 2015, 09:59:52 am
John, you've really done some fine work on this.  Now go build something to keep you in hops.

Thanks.. I may build a small batch of these but can't see tooling up a fancy package. The parts cost even in small quantity don't amount to much, while the expectation of a fair price for an outlet checker is likewise low.

Even if this is the only one that actually detects the dangerous wiring scenarios.  8)

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 17, 2015, 08:30:02 am
Thanks.. I may build a small batch of these but can't see tooling up a fancy package. The parts cost even in small quantity don't amount to much, while the expectation of a fair price for an outlet checker is likewise low.

Even if this is the only one that actually detects the dangerous wiring scenarios.  8)

JR

JR - The input buffer is brilliant.... When can I get one to play with?

Mike
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 17, 2015, 12:43:54 pm
JR - The input buffer is brilliant.... When can I get one to play with?

Mike

I can send you my one prototype, I'm kind of finished with it for now. It is a mess and I will need to check the solder connections, since this same prototype has been torn down and rebuilt at least three times. It is kind of dangerous with lots of exposed energized components, but I wrapped some clear tape around the circuitry. I literally don't have enough 400V diodes laying around to build another, I used up all I bought the last time between this and my smart GFCI outlet.

I am thinking of laying out a PCB for this using all SMD parts, but before I do that I need to figure out how I want to package this (I can probably get 20-30 boards from a single prototype panel).

I bought a cheap 3 lamp outlet tester, and sure enough it says that my RPBG test outlet measures as good.  >:( >:( Why does UL let them sell those? (They are UL listed)  That's F'n dangerous. My way is slightly more expensive, but mine actually works.  I've seen the 3 lamp testers as cheap a $2 something so nothing much inside, my guts are probably <$2 in decent qty, which means a $10+ tester.  While the only one that works correctly should command a price premium.

I plan to take apart the cheap 3 lamp tester to see if i can easily fit a PCB inside, but first I need to get it apart without destroying it.

Let me know your snail mail address (you have my email). I may send you my smart outlet prototype also, which works,  while I really don't plan to ever make more of those.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 17, 2015, 03:33:41 pm
For those of you (still) following along, here's the schematic of a simple 3-light outlet tester you can buy anywhere for less than $5 or so. As you can see, it's just a handful of resistors and neon lamps. Probably millions of these have been produced over the last 50 years or more. But as JR alluded to, and I've written about extensively, they can't identify several very dangerous miswiring conditions, especially an RPBG (Reverse Polarity Bootleg Ground).

Title: Re: brain storm an optimal human safety system for back line
Post by: Bob Leonard on June 18, 2015, 05:12:06 pm
Hey guys,
I've been following along and props for all the hard work that's been done. Makes me wish I had more leisure time. How about a couple of pictures showing construction and component placement. Specifically JR, are the type and values relevant for the diodes in your schematic. Thanks.
 
I've been using one of these lately. Simply brilliant for the price.
 
 http://www.sears.com/craftsman-circuit-breaker-finder/p-03482021000P?prdNo=9&blockNo=9&blockType=G9 (http://www.sears.com/craftsman-circuit-breaker-finder/p-03482021000P?prdNo=9&blockNo=9&blockType=G9)
 
 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 18, 2015, 06:06:04 pm
Hey guys,
I've been following along and props for all the hard work that's been done. Makes me wish I had more leisure time. How about a couple of pictures showing construction and component placement. Specifically JR, are the type and values relevant for the diodes in your schematic. Thanks.
 

Thanx Bob-

The rectifiers in my prototype are typical 1n4004 400V 1A. They don't need to be 1A but 400V reverse breakdown is useful.

The proto is kind of ugly, built up on a generic .100" centers standard pads board. The spacing was a little tight for the MOSFET which is actually .050" centers for pin spacing but they put the drain on the tab too and made it the center pin so i could bend up the center pin and solder the gate and source on 0.100" pads and grab the drain from the tab on the other side of the part. These modern SMD parts are crazy small and hard to breadboard with. 

I already sent my only working proto to Mike to run through it's paces on his torture bench. I hope it still works after the USPS gets finished with it. I built up and tore down 3 different versions, before hitting on that final design. And that one took two tries to get it working adequately, so lots of questionable tack solder connections, by an old man with bad eyesight.  ;D ;D

I am thinking about laying out a SMD board for this that could be really tiny... Absolutely none of the parts need to be very large, or dissipate much power. I suspect the form factor will be dominated by what I decide to build this into.

This could be built into any product with a 3 wire line cord. I could build it into an empty plug housing.

Any suggestions?

I am not enthusiastic about tooling up a slick package, but could see selling assembled working PCBs in small quantity that others can built into whatever.  A mounting screw head could double as the touch contact. Color code is pretty simple green=good, red=bad.

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on June 18, 2015, 07:06:40 pm
JR, if there is room, might you put your device inside a 16693 Leviton, 15 Amps, 120 Volts, NEMA 5-15P, GFCI Plug, Grounded - BLACK?  Bob, would that work for you on a vintage amp? (Sorry for not inserting a link; I haven't figured out how to do that from my old iPhone.  I was looking at the ATI Electrical website.)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 18, 2015, 08:21:23 pm
Yup probably...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 18, 2015, 09:35:10 pm
I already sent my only working proto to Mike to run through it's paces on his torture bench.

JR

Bring me a brain, Igor...
Title: Re: brain storm an optimal human safety system for back line
Post by: Bob Leonard on June 18, 2015, 11:10:15 pm
Would the one from Abby Normal work?
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on June 19, 2015, 02:24:50 am
Would the one from Abby Normal work?

Couple of shots of a long band Abby Normal and the Detroit Lean:

(https://thelongshotist.files.wordpress.com/2015/04/yuri-abby-normal.jpg)

(http://imgick.cleveland.com/home/cleve-media/width620/img/berea/photo/15418258-standard.jpg)
Title: Re: brain storm an optimal human safety system for back line
Post by: Rob Spence on June 19, 2015, 11:48:26 am
Thanx Bob-

The rectifiers in my prototype are typical 1n4004 400V 1A. They don't need to be 1A but 400V reverse breakdown is useful.

The proto is kind of ugly, built up on a generic .100" centers standard pads board. The spacing was a little tight for the MOSFET which is actually .050" centers for pin spacing but they put the drain on the tab too and made it the center pin so i could bend up the center pin and solder the gate and source on 0.100" pads and grab the drain from the tab on the other side of the part. These modern SMD parts are crazy small and hard to breadboard with. 

I already sent my only working proto to Mike to run through it's paces on his torture bench. I hope it still works after the USPS gets finished with it. I built up and tore down 3 different versions, before hitting on that final design. And that one took two tries to get it working adequately, so lots of questionable tack solder connections, by an old man with bad eyesight.  ;D ;D

I am thinking about laying out a SMD board for this that could be really tiny... Absolutely none of the parts need to be very large, or dissipate much power. I suspect the form factor will be dominated by what I decide to build this into.

This could be built into any product with a 3 wire line cord. I could build it into an empty plug housing.

Any suggestions?

I am not enthusiastic about tooling up a slick package, but could see selling assembled working PCBs in small quantity that others can built into whatever.  A mounting screw head could double as the touch contact. Color code is pretty simple green=good, red=bad.

JR

I don't have a packaging suggestion but want to say that I am sure a lot of folks who do work at older buildings would love one of these.

I counted and I found 50 people I know up here in the northeast that would want one. I know I do.



Sent from my iPad using Tapatalk HD
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 19, 2015, 12:38:04 pm
The need is not liimited to older buildings.  I was finishing up a project last month-the GC decided to wire in the microwave receptacle to "help" me out.  Wired one receptacle-and wired it reverse polarity.  Just the kind of help I need!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 19, 2015, 01:31:11 pm
I don't have a packaging suggestion but want to say that I am sure a lot of folks who do work at older buildings would love one of these.

I counted and I found 50 people I know up here in the northeast that would want one. I know I do.



Sent from my iPad using Tapatalk HD

I have no desire to undertake a major commercial project. It seems the companies selling the cheap outlet testers that don't work should be interested in something that does work. A real commercial version would require UL approval (like the ones that don't work). This UL approval only confirms that it won't burn your house down or kill the operator.

When I find a convenient form factor to package this (probably built into something else) I can make these in modest volumes. Since the PCB will be so small the standard prototype panel would probably make 20 or 30 of these. But I won't start the PCB layout until I have a physical packaging plan. 

I am too old to hand assemble these in quantity, but that can be farmed out.

Your mission is to think of something slick to build these into. I like the idea of building it into a GFCI plug, but that doesn't sound cheap. I like cheap, while the GCI plug could provide protection in use. Perhaps I need to revisit building this into a GFCI outlet strip. Maybe with a stinger cap ground to cover more bases and allow the show to go on even when revealing adverse conditions. 

JR

PS: If any real company is interested feel free to contact me.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 22, 2015, 03:28:23 pm
JR - Just received your UOT (Ultimate Outlet Tester) in the mail, and it appears to still be in one piece. So I'll start testing tonight and report back on how it works.

BTW: I do have someone who might be interested in manufacturing your design if it works as advertised. Call me anytime to confer.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 22, 2015, 04:26:09 pm
JR - Just received your UOT (Ultimate Outlet Tester) in the mail, and it appears to still be in one piece. So I'll start testing tonight and report back on how it works.

BTW: I do have someone who might be interested in manufacturing your design if it works as advertised. Call me anytime to confer.

Sweet....  we can work on that name... I like something like "the only accurate tester" or something like that.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 22, 2015, 04:52:18 pm
Sweet....  we can work on that name... I like something like "the only accurate tester" or something like that.

JR

Can I still call my Soviet outlet simulator the Discombobulator? ;)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 22, 2015, 04:55:22 pm
Can I still call my Soviet outlet simulator the Discombobulator? ;)
You could call it a newbie killer...

Seriously do you incorporate a GFCI in front of that re-matrix switch so it will be harder to hurt the meat puppets with dangerous settings?

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 22, 2015, 05:08:14 pm
You could call it a newbie killer...

Seriously do you incorporate a GFCI in front of that re-matrix switch so it will be harder to hurt the meat puppets with dangerous settings?

JR

Yes I use an in-line extension cord GFCI which opens up if there's an external fault to ground downstream. And the rotary switches make it impossible to cross-connect the Line, Neutral and Ground lines to a common outlet contact. I've done a lot of thinking about this...

BTW: I'm going to build an extra one of these if anyone would like to try it out. Only experienced engineers and electricians need apply since it can create some really dangerous outlet conditions. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 22, 2015, 05:57:35 pm
Think I'll hard-wire a GFCI plug into the power cable for my Outlet Confuser Matrix (is that a better name?). That way the GFCI can't be taken out of the circuit by someone else not as careful as me. The OCM will be able to generate lethal outlet conditions if you plug something like a guitar amp into it, so I guess it needs hard-wired protection.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 22, 2015, 07:01:29 pm
It's literally a mains wiring fault simulator...  unless that name is already taken.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 22, 2015, 07:20:01 pm
Another thought would be to install a momentary (insulated) switch that must be held closed in order to energize the receptacle.  That would still leave one hand free to use a DMM probe to discover the fault-but prevent anyone from trying to use it to power any sort of load.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 23, 2015, 04:28:39 pm
Well, JR's Frankenstein circuit board arrived, and I've just run an initial test using my standard 3-outlet comparison strip. While I don't have all combinations of outlet failures represented here, it's enough for me to verify that his circuit can correctly detect the difference between a ground at earth potential, and one at 120-volts. See below. Now I need to rig up a test that will let me vary the ground and neutral voltages to find the threshold where the LEDs turn on. Should be interesting.... 8)
Title: Re: brain storm an optimal human safety system for back line
Post by: TJ (Tom) Cornish on June 23, 2015, 04:31:42 pm
Well, JR's Frankenstein circuit board arrived, and I've just run an initial test using my standard 3-outlet comparison strip. While I don't have all combinations of outlet failures represented here, it's enough for me to verify that his circuit can correctly detect the difference between a ground at earth potential, and one at 120-volts. See below. Now I need to rig up a test that will let me vary the ground and neutral voltages to find the threshold where the LEDs turn on. Should be interesting.... 8)
Is JR's tester rated at CAT IV 1000v?  :)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 23, 2015, 04:38:25 pm
Is JR's tester rated at CAT IV 1000v?  :)

No... but if you have enough money to spend,,,,

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: TJ (Tom) Cornish on June 23, 2015, 04:38:59 pm
No... but if you have enough money to spend,,,,

JR
I heard that bubble wrap has a pretty high dielectric strength.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on June 23, 2015, 04:44:34 pm
Is JR's tester rated at CAT IV 1000v?  :)

Do you need a cat to test it on?
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 23, 2015, 04:46:20 pm
I heard that bubble wrap has a pretty high dielectric strength.
Bubble wrap PLUS shipping tape. Kids, don't try this at home... ;)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 23, 2015, 05:00:27 pm
I heard that bubble wrap has a pretty high dielectric strength.

If that's in a pink bubble wrap bag, that's anti-static so slightly conductive...Probably not a good idea to leave it in one of those bags while powered up. I wrapped the board with clear label tape so should not be very dangerous, but you know, be careful. I don't remember what I shipped it in, but I only have anti-static bags laying around.

Looking at the pictures the red LED has a little leakage current, so it is only really on for the RPBG connection. I can probably tweak resistor values some to fix that... those LEDs are a few decades old so efficiency is not like modern stuff..

@ Mike  re: sensitivity... I think there are 10k Rs in series with the LEDs so the red Ground LED may start to glow with tens of volts. The leakage now is from the pull-up R that keeps the human capacitor from discharging.

The test is not smart enough to detect bootleg ground, vs. normal ground, just ground present or open circuit.

For the RPBG, it indicates green that ground is present, yellow that neutral is hot, and red that ground is hot...

JR

PS: I'm really glad it still works, that proto was torn down and rebuilt multiple times.



Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 23, 2015, 07:15:11 pm
Yes, be careful-it would be a rather sad chapter to this odyssey for the chief instructor of No Shock Zone to become the introductory illustration for whoever inherits No Shock Zone. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on June 23, 2015, 07:28:49 pm
Yes, be careful-it would be a rather sad chapter to this odyssey for the chief instructor of No Shock Zone to become the introductory illustration for whoever inherits No Shock Zone.

Not to worry. I've been thoroughly trained in electrical safety by OSHA back in my youth, and very careful around this stuff. I'm still a little bit scared around live circuits, and that's a good thing.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on June 24, 2015, 12:29:21 pm
Two (three?) brilliant pieces. It's been enlightening following along (just reading).
I know it has been alluded to, but is this proper outlet tester someone like Fluke or GB would purchase the rights to?  Of course, if you show it to them without a patent, you may as well give it away.  And patents, while probably not as expensive as UL listing, are probably are not cheap.


To me it seems like coding, but with electricity - with real penalties for mistakes.


Anyway, the modded stinger-GFCI is on my short list to build a few.
The smart power strip is probably beyond my skills - but damn, I'd like to have one or two.
When you start building that proper outlet tester, (notice I did not say manufacture) or sell the rights to some SMART company, put me on the list for one or so.


Thanks for sharing your work (and that of your night team). 
(one day, you have to rewire that house. Seriously.)


frank
ps. A voltmeter, too?  Single plug solution.



Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 24, 2015, 01:20:14 pm
Two (three?) brilliant pieces. It's been enlightening following along (just reading).
I know it has been alluded to, but is this proper outlet tester someone like Fluke or GB would purchase the rights to? 
That is my desire... I actually get angry about the outlet testers sold now that indicate RPBG wired outlets as safe.  :o
Quote
Of course, if you show it to them without a patent, you may as well give it away.  And patents, while probably not as expensive as UL listing, probably are not cheap.
I have 9 patents under my belt so yes we are talking a couple $10k, it will still need UL approval on top of that. UL is similar price range but probably a little less expensive than patent.

In my judgement this could be patented... I do not see anybody else doing this so apparently it is not that obvious.  8) My understanding of the US IP law is that I would need to file within a year of publication, so that clock is running.

I worry a little that making this completely free for all to use, might discourage a serious manufacturer from investing in developing their version of this. I am not looking for more work or some big payday so I will work with anybody serious about making this. If a major wants to pay for the patent application, we can do that too. If instead they decide to just copy me, I only insist that they make it correctly.. 
Quote


To me it seems like coding, but with electricity - with real penalties for mistakes.


Anyway, the modded stinger-GFCI is on my short list to build a few.
Yes, I asked UL about the stinger cap GFCI on a contact form on their website a few weeks ago, but apparently they don't read or answer those.
Quote
The smart power strip is probably beyond my skills - but damn, I'd like to have one or two.
I already lost interest in the smart power strip...Too expensive and not working at all unless everything is perfect is too much to expect... The stinger GFCI will work even in the worst of cases, and still protect the civilians.
Quote

When you start building that proper outlet tester, (notice I did not say manufacture) or sell the rights to some SMART company, put me on the list for one or so.

Still thinking about what to build it into... but I'll probably build a few tens of these (minimum prototype PCB order).
Quote
Thanks for sharing your work (and that of your night team). 
(one day, you have to rewire that house. Seriously.)


frank
Nah, I do want to add a ground wire connection to the outlet in my laundry room (a few feet from the panel) but I have faith in GFCI to protect me from serious faults elsewhere.  In fact I still haven't put a GFCI outlet in the laundry room yet.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on June 24, 2015, 01:30:43 pm
Maybe something like a Kickstarter campaign to fund patent and UL approval?
Heck, if relatively unknown folks can get money for making CDs, surely this could get support. (that's my eternal optimist speaking)
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 24, 2015, 01:50:43 pm
Maybe something like a Kickstarter campaign to fund patent and UL approval?
Heck, if relatively unknown folks can get money for making CDs, surely this could get support. (that's my eternal optimist speaking)
frank

I could afford*** to patent and file UL if I really wanted to but I am not looking for another full time business. If I did a kickstarter campaign that would mean hundreds of new bosses....no thanx.

JR

*** Just because I could doesn't mean I should... I may need to keep buying my own beer for several years.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on June 24, 2015, 05:58:27 pm
I could afford*** to patent and file UL if I really wanted to but I am not looking for another full time business. If I did a kickstarter campaign that would mean hundreds of new bosses....no thanx.

JR

*** Just because I could doesn't mean I should... I may need to keep buying my own beer for several years.
FWIW, I haven't seen kickstarter folks have input to the artistry of a CD they contribute to, but those are not "products".
I do understand the full-time business. 
Patent protection is minimal.  Even with a patent, it wouldn't take much of a design change to have it ruled as "different art".


And remember, BOSS spelt backwards is Double "S" "OH" "BE". 
Never mind.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 24, 2015, 06:02:49 pm
One comment on the GFCI-stinger.  Someone, on another thread, alluded to doing this in an installed GFCI.  IMO, this is a violation of Code and a bad idea.  Since this is primarily for commercial applications and most commercial uses metallic boxes and given that the conductors entering a given box are not GFCI protected-the device box and mounting strap for the GFCI need to be solidly grounded to trip OCPD in the event of a fault.

A GFCI protected strip is an entirely different situation.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 24, 2015, 06:36:02 pm
One comment on the GFCI-stinger.  Someone, on another thread, alluded to doing this in an installed GFCI.  IMO, this is a violation of Code and a bad idea.  Since this is primarily for commercial applications and most commercial uses metallic boxes and given that the conductors entering a given box are not GFCI protected-the device box and mounting strap for the GFCI need to be solidly grounded to trip OCPD in the event of a fault.

A GFCI protected strip is an entirely different situation.

OCPD Obsessive Compulsive Personality Disorder? I ASSume you mean blow the branch fuse/breaker?

+1  The legal status of this is still TBD WRT UL ground labeling et all. The 0.15uF stinger cap is sized to exceed the 5mA GFCI fault current threshold, not 15A. If there is an external mains voltage fault... It will not trip any breakers but the path will be current limited to below hazardous levels. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 24, 2015, 10:53:43 pm
OCPD=Over Current Protective Device so yes a fuse or circuit breaker.

My concern is the difference between an installed GFCI and a portable device.

If you use the stinger cap on an installed GFCI-especially in a a metal box, then there is potential for non-GFCI protected conductors to come in contact with the box(happens more often than you would think).  Since the stinger cap will not trip the OPCD, then the box is energized thus energizing the ground pin on the GFCI-from a conductor that is not GFCI protected creating a hazard.

I think the idea is a good one-but good ideas wrongly applied can be bad.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 24, 2015, 11:03:29 pm
OCPD=Over Current Protective Device so yes a fuse or circuit breaker.

My concern is the difference between an installed GFCI and a portable device.

If you use the stinger cap on an installed GFCI-especially in a a metal box, then there is potential for non-GFCI protected conductors to come in contact with the box(happens more often than you would think).  Since the stinger cap will not trip the OPCD, then the box is energized thus energizing the ground pin on the GFCI-from a conductor that is not GFCI protected creating a hazard.

I think the idea is a good one-but good ideas wrongly applied can be bad.
The junction box can and probably should be grounded . Just the Ground lead feeding the outlet needs to be cap coupled for stinger GFCI.

But still agreed,,, not intended for permanent install... since by definition a permanent junction box being permanent should be wired correctly. This is most useful IMO when plugging into unknown power drops.

Performance spaces may be different again, but still if all of the power drops in the venue are good there is no problem.  Permanent back-line outlets where the FOH is often on tails or semi-permanant wiring might have some merit.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 25, 2015, 11:16:14 am

The junction box can and probably should be grounded . Just the Ground lead feeding the outlet needs to be cap coupled for stinger GFCI.


That would work-except mounting strap for the receptacle is typically connected to the receptacle ground so the cap would be shorted out and ineffective.  It would almost have to be a custom built GFCI receptacle (an isolated ground GFCI !)-and that would have to be UL listed to meet Code-and as you pointed out the market probably would not justify the investment.

Not trying argue-just trying to make sure people think through possibilities.  In another thread, someone asked about tying the grounds on a couple of Furman's together that were fed by 2 separate power sources.  Fed from 2 separate GFCI/stingers would place 2 caps in parallel thus doubling the potential current.  GFCI's should still protect-but now this does mandate that all potential sources be GFCI protected.

It is usually relatively easy to get things to work correctly as intended-not always so easy to anticipate all the incorrect ways something might be used-which I am sure you understand after a career in design.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 25, 2015, 12:49:40 pm
That would work-except mounting strap for the receptacle is typically connected to the receptacle ground so the cap would be shorted out and ineffective.
Indeed it is... I remembered that last night after the lights were out but just before my head hit my pillow. I did not get up again last night.

My smart GFCI outlet proto is mounted into a plastic junction box but that's probably not to code either.
Quote
It would almost have to be a custom built GFCI receptacle (an isolated ground GFCI !)-and that would have to be UL listed to meet Code-and as you pointed out the market probably would not justify the investment.
I think there may be exceptions for use with a non-bonded ground as long as the status or non-status of the ground is labelled.
Quote
Not trying argue-just trying to make sure people think through possibilities.  In another thread, someone asked about tying the grounds on a couple of Furman's together that were fed by 2 separate power sources.  Fed from 2 separate GFCI/stingers would place 2 caps in parallel thus doubling the potential current.  GFCI's should still protect-but now this does mandate that all potential sources be GFCI protected.
We can think this to death...  The stinger cap current is just enough to trip the GFCI (around 7mA IIRC) so two or three in parallel are still not deadly. It takes some tens of mA to get stuck to the current.

Another concern is stinger mixed with a non-stinger outlet used on say guitar pedals, where the stinger cap is now shorted out and the musician is at risk again. The good news is that my tester tells me the stinger cap prevents ground loop hum should that dual ground path scenario occur, but the guitar player is not protected from external mains faults (like RPBG at FOH or RPBG on the second outlet).
Quote
It is usually relatively easy to get things to work correctly as intended-not always so easy to anticipate all the incorrect ways something might be used-which I am sure you understand after a career in design.
Yup... while we can debate how easy it is to get a hum free guitar rig, and how much of a risk this (hot mic) is. But I do not debate that people are remarkably creative about operating things wrong.

I believe that the stinger equipped GFCI power strip is about as harmless to human safety as I can imagine.

#1 if the guitar amp goes rouge and dumps current to it's chassis, it will trip the GFCI removing power.
#2 if the FOH has a hot ground, or if the outlet is wired RPBG the hazard will be current limited to 7 mA.

Lifting the guitar amp ground (as many musicians still do) will actually be less dangerous for RPBG situations, while providing zero protection agains internal amp faults. 

Only my smart outlet lifts ground and releases power if it detects excessive current in the ground. This is too complicated and expensive to be commercial. and UL will have an even harder time blessing a safety ground path that goes through a normally open relay.

I am addressing a fairly narrow type of fault. Musicians are more likely to expose themselves to multiple different branch circuit grounds than normal consumers. This is probably rare enough that UL wouldn't want to make special rules.

FWIW I also like the idea of using wireless mics for guitar players (and baptismal clergy, and swimming pool karaoke, and etc). A far cheaper solution to mic shock hazard would be an insulated outer covering for mics. A dynamic mic could even use a stinger cap ground, but phantom powered mics would not be happy.   

Note: I have seen a special line cord/plug set that senses current in a ground shield and open up power if a threshold current is exceeded. A variant on this for a GFCI power strip might work and already be listed. (I'll check that out).

JR

[edit] OK ignore that protected line cord...it senses for current shield to neutral, so ground is either pass through or missing... not much help there.  [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 25, 2015, 03:24:35 pm
"I believe that the stinger equipped GFCI power strip is about as harmless to human safety as I can imagine."

I agree 100%-and by keeping it as power strip, you avoid a whole can of worms when it comes to building it correctly and Code compliance.  Probably the ideal way to build this is with something like this:

http://www.leviton.com/OA_HTML/ProductDetail.jsp?partnumber=GFM20-3C&section=40493&minisite=10251

with the ground from the cord going to the cap.  This way any hot conductors in the power strip proper are   GFCI protected. 

Making it a portable power strip permits you to control its use-since it is designed for a specific use.  Code has many reference to "engineering supervision" or "under supervision of qualified personnel."  So an argument can be made for exceptions in a controlled supervised manner.  Installed receptacles in public places  are not controlled by any means!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 25, 2015, 04:23:03 pm
same color as mine...


JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 25, 2015, 06:55:18 pm
:) I figured it was safe to assume yours was done correctly-just wanted to make sure that copycats understood that some of the nuances really were important-not just happenstance.
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve Loewenthal on June 25, 2015, 07:18:31 pm
So I started at the beginning of the thread and read all of page 1. I'll probably read 1 page a day, even though it looks like I can already see how it ends. Looks like a good ending and I am confident I'll learn a few things as my read progresses.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 11, 2015, 11:14:17 am
While I am not happy with the price for onsey twosey ($7+), I am leaning towards this for packaging my outlet tester. (http://www.leviton.com/OA_HTML/ibcGetAttachment.jsp?cItemId=0GK1uWSYxgXE0rxRsIklQw&label=IBE&appName=IBE&sitex=10251:22372:US)

I should be able to include the LED indicators inside the transparent area, and connect the touch probe to one of the assembly screws. I might want to put LEDs on both sides of the PCB so orientation of the plug is not a problem.

I ordered a couple of these to see what they look like. If I build some based on this I hope to get them for a lower price.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 15, 2015, 07:58:23 pm
Here is first pass layout. I should get samples of my clear plugs in a few days. Then I will start tweaking physical layout I may need to increase spacing between line and Neutral/ground.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 22, 2015, 03:58:25 pm
Got my clear plugs in and working area visible from the outside is smaller than I expected but still usable.

I have rearranged the components so the LEDs are up near the plug end so they can be seen from outside. LEDs doubled up with top and bottom LEDs in series, so plug in orientation doesn't affect visibility.

Not elegant but looking to connect the two metal cable clamp screws to the touch probe.

JR

PS I want one of these....but i don't want to hand build a bunch of these... tiny SMD parts close together.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 26, 2015, 10:17:25 pm
Well I ordered prototype circuit boards (I think). Found a silly cheap vendor from China with a price that is embarrassingly low($14), but in a classic case of you don't get what you don't pay for, the customer service is questionable.

My original order was kicked because my gerber files had different file extensions than they like,,, My version of layout software is probably 20 years old... :-) So far I don't know (yet) that my updated file package has been received and acceptable.

They were so cheap if I don't hear for a few more days I may order from somebody else.

I still need to order some (SMD) parts so no hurry...

Progress and forward motion.

JR

PS I looked at slick ways to execute the touch contact (using conductive rubber) but decided to KISS... so I'll have a right angle pin header sticking out of the line cord hole. I guess you could attach a connector to the header for a remote touch control.  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 27, 2015, 12:33:54 pm
I finally got a confirmation that my PCB order has been accepted, batched up, and sent to China for processing.  ;D

I just ordered $60 worth of parts to stuff 10 prototypes. It really sucks buying electronic parts in small quantity... >:( In real production quantities this could be pretty reasonable....  ignoring the painful labor of a senior citizen trying to see SMD parts.  :o

JR

[update] 
Parts arrived today...
PCBs shipped from hong kong yesterday 7/29 (airmail 1-8+ weeks).  I don't expect airmail to take 8 weeks so hopefully next week sometime. 
[/update]
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 30, 2015, 01:54:22 pm
Parts arrived today...
PCBs shipped from hong kong yesterday 7/29 (airmail 1-8+ weeks).  I don't expect airmail to take 8 weeks so hopefully next week sometime. 
I've been ordering lots of parts from China lately, and even though they quote 4 to 6 week shipping, I've been getting many orders in 10 days or less. And that's with the "free" slow shipping. Pretty crazy.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 30, 2015, 04:13:07 pm
I've been ordering lots of parts from China lately, and even though they quote 4 to 6 week shipping, I've been getting many orders in 10 days or less. And that's with the "free" slow shipping. Pretty crazy.
For example, I needed some 6x20mm fuses for my FOG Matrix, and ordered a 10 pack from China for 99 cents INCLUDING shipping. Not 99 cents each, mind you. The entire order cost 99 cents for 10 fuses including shipping and just came in the mail today. I ordered these on July 14th, so it took exactly 16 days for them to arrive. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 30, 2015, 04:55:14 pm
Yup I've found "slow-boat" (surface) shipping from China to be weeks, not months. These boards are supposed to ship air mail, so I expect them next week, no matter how many months they state as worst case.

 JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 11, 2015, 01:06:58 pm
Still waiting for my PCBs coming slow-plane air mail...
======
Today a friend (Gene Pink)  sent me a picture of an outlet tester he built back in the '80s

Using multiple neon lamps and multiple touch contacts.. Lamps that light on the green side were good, lamps on the red side lighting were bad,,,

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 18, 2015, 11:25:28 am
Well my slo-plane airmail arrived from China today... looks like it took 3 weeks or so.

I am busy today doing real work, but will populate a board or two when I can.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on August 18, 2015, 01:53:05 pm
My original order was kicked because my gerber files had different file extensions than they like,,, My version of layout software is probably 20 years old... :-) So far I don't know (yet) that my updated file package has been received and acceptable.

JR
If you can, send ODB++ files.  Gerber is open to a lot of interpretation.  If the Gerbers were 274X they shouldn't care what extensions were used.  Although in my CM life, it drove me nuts when people used the extension to denote which layer it was.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 18, 2015, 02:13:17 pm
If you can, send ODB++ files.  Gerber is open to a lot of interpretation.  If the Gerbers were 274X they shouldn't care what extensions were used.  Although in my CM life, it drove me nuts when people used the extension to denote which layer it was.
Yup my files were 274x gerbers... But for $14 flat fee I don't expect much hand holding... I don't mind renaming the files.

24 boards for $14 is just crazy cheap ($0.58).... admittedly they are tiny boards but quality looks OK from quick inspection.

3 weeks shipping is not great, but you get what you pay for and I didn't pay for fast...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on August 18, 2015, 02:28:04 pm
Sounds like one panel.  There might have been more that they threw away.  Pretty darn good price for a one off.  Most of the big shops are retooling for any layer blind/buried vias and there's a lot of left over conventional capacity.  One panel, double sided, probably only spent a day in the shop.  Cost of tracking it though the shop probably exceeds the parts themselves.  If you don't mind, I'd like to know who did this for you.  We occasionally need little test interface boards.

A couple of years ago I was trying to find someone to make a small batch of boards for testing solderpastes down to the smallest features.  Ended up with Tripod in China as the only people who could make it and got very good pricing as well compared to local shops who couldn't get the small features reliably.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 18, 2015, 04:00:12 pm
Sounds like one panel.  There might have been more that they threw away.  Pretty darn good price for a one off.  Most of the big shops are retooling for any layer blind/buried vias and there's a lot of left over conventional capacity.  One panel, double sided, probably only spent a day in the shop.  Cost of tracking it though the shop probably exceeds the parts themselves.  If you don't mind, I'd like to know who did this for you.  We occasionally need little test interface boards.

A couple of years ago I was trying to find someone to make a small batch of boards for testing solderpastes down to the smallest features.  Ended up with Tripod in China as the only people who could make it and got very good pricing as well compared to local shops who couldn't get the small features reliably.
Sure it's no secret... I got the tip on another DIY website. I've been buying PCB from china for years. even when I order them from US or Canada.  :o

http://dirtypcbs.com/ (http://dirtypcbs.com/)

they offer a few fixed price deals my $14 was for 5x5 cm, they also have a $25 10x10cm deal...

the proto board count is nominally 10 pcs but +/- a few... My + was 24 pcs,,,

I suspect they nest a bunch of different projects together to fill a standard panel and I got lucky, probably the last job on that panel.

Unless you are willing to wait 3 weeks for the free shipping like I did you can upgrade to quicker shipping, costing a bunch more than the boards, but that the nature of things these days.

JR

PS I've used other chinese proto board shops that were more like $100 for how ever many boards you can get out of a standard panel.. but this deal is crazy cheap.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on August 18, 2015, 05:01:16 pm
I love it!  readme's? get out of here :)

5/5 on 1oz ain't bad for cheap.  Even colored mask which can be a pain to image, and they're holding 3mil webs with it.

There used to be a proto shop out here called NBS which literally stood for No B.S.  Box-o-parts and a napkin, no problem.  Unfortunately they got some bigger contracts, expanded and couldn't sustain it. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 18, 2015, 06:27:44 pm
I love it!  readme's? get out of here :)

5/5 on 1oz ain't bad for cheap.  Even colored mask which can be a pain to image, and they're holding 3mil webs with it.

There used to be a proto shop out here called NBS which literally stood for No B.S.  Box-o-parts and a napkin, no problem.  Unfortunately they got some bigger contracts, expanded and couldn't sustain it.

Yup the website is a bridge to a taobao supplier in china... so no speaky the english at the board house.

I always thought read-me's  were redundant .

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 19, 2015, 11:36:06 am
Not news but worth reviewing...

(http://www.digikey.com/~/media/Images/Article%20Library/TechZone%20Articles/2015/July/KISS%20Your%2060601-1%20Medical%20Power%20Supply/article-2015july-kiss-your-60601-1-fig1.jpg?la=en)

FWIW I've felt current < 1 mA but not a big deal. The actual current you will experience often depends hugely on skin resistance which varies with moisture (sweat).

Note: I sized the GFCI stinger cap to be > 6 mA to trip the GFCI but < 10 mA to be below the let-go threshold. 

The probe current for outlet tester is perhaps tens of uA...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on August 19, 2015, 01:42:59 pm
Not news but worth reviewing...

(http://www.digikey.com/~/media/Images/Article%20Library/TechZone%20Articles/2015/July/KISS%20Your%2060601-1%20Medical%20Power%20Supply/article-2015july-kiss-your-60601-1-fig1.jpg?la=en)

FWIW I've felt current < 1 mA but not a big deal. The actual current you will experience often depends hugely on skin resistance which varies with moisture (sweat).

Note: I sized the GFCI stinger cap to be > 6 mA to trip the GFCI but < 10 mA to be below the let-go threshold. 

The probe current for outlet tester is perhaps tens of uA...

JR

Good chart. Plus it's good to be aware that skin resistance is highly non-linear in nature and varies by voltage. That is, your body doesn't follow a simple I=E/R relationship like a resistor. It's a bit  logarithmic in nature, with current rising more rapidly than the voltage due to a "punch through" effect of the epidermis skin layer. Once the epidermis layer "insulation" has been breached, then there's a much higher current flow. I generally use 1,500 ohms as a base calculation for electrocution, but as JR also point out, this changes a lot with skin moisture. Of course, I can think of few situations more likely to induce maximum shock current than standing on stage with sweaty hands on your metal guitar strings and touching a wired mic with your wet lips. Well, perhaps standing in a baptismal pool with a wired mic or electric guitar in your hand should be at the top of the "Don't Do It" list.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 19, 2015, 02:12:19 pm
I've thought about this a bunch and I don't know that the skin resistance is non-linear, but the human body is not a simple homogeneous resistor. Our core which is like a dilute salt water solution is pretty conductive. The skin layer is not a great conductor especially when dry, but rarely completely dry..

The crusty old electricians who show off by grabbing live wires have (dry) callused hands to protect them.

Another variable is how tightly you grip the conductor.. grabbing tighter will deliver lower resistance.

Since electricity follows the lowest impedance path, it doesn't travel from hand to hand just on your outside skin, but inside your body where the bad stuff happens.

A high voltage shock may punch through the skin layer and into the more conductive core.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on August 19, 2015, 06:52:47 pm
I've thought about this a bunch and I don't know that the skin resistance is non-linear, but the human body is not a simple homogeneous resistor. Our core which is like a dilute salt water solution is pretty conductive. The skin layer is not a great conductor especially when dry, but rarely completely dry..

The crusty old electricians who show off by grabbing live wires have (dry) callused hands to protect them.

Another variable is how tightly you grip the conductor.. grabbing tighter will deliver lower resistance.

Since electricity follows the lowest impedance path, it doesn't travel from hand to hand just on your outside skin, but inside your body where the bad stuff happens.

A high voltage shock may punch through the skin layer and into the more conductive core.

JR

I have heard (anecdotally) that 12V can deliver a fatal shock, if the resistance between the point of contact and the moist tissues of the body is low enough. I am not willing to test the veracity of this claim.

So don't go and pinch your fingers in the jumper cables when you hook up to your car battery.  :o
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 19, 2015, 08:31:52 pm
I have heard (anecdotally) that 12V can deliver a fatal shock, if the resistance between the point of contact and the moist tissues of the body is low enough. I am not willing to test the veracity of this claim.

So don't go and pinch your fingers in the jumper cables when you hook up to your car battery.  :o
You can't look at voltage in isolation. Current is what does the damage and current is dependent on voltage "and" resistance.

A 1.5V AA cell could kill you if someone drives it deep into your heart.  :'(

!2V seems relatively harmless in most ways we would normally encounter it. I wouldn't take a bath with a car battery in the tub, but the acid and mess might be worse than the electrical shock hazard.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on August 20, 2015, 08:43:09 am
You can't look at voltage in isolation. Current is what does the damage and current is dependent on voltage "and" resistance.

A 1.5V AA cell could kill you if someone drives it deep into your heart.  :'(

!2V seems relatively harmless in most ways we would normally encounter it. I wouldn't take a bath with a car battery in the tub, but the acid and mess might be worse than the electrical shock hazard.

JR
If you have cuts on your hands, even touching the copper tips on 12-volt jumper cables can be very painful since your epidermis layer has bee breached, but I don't think it's life threatening. And a 9-volt battery on the tongue is pretty zippy, but the current would never even get near your heart. According to some charts I've seen, DC shocks require about 3X as much voltage as AC shocks for human electrocution. That's because 60 Hz seems to be the perfect frequency to disrupt human heart rhythm and put it into ventricular fibrillation. When the paramedics arrive and use a de-fibrillator on you, there's a bunch of capacitors dumping DC into your chest and heart. That causes all your heart muscles to contract at the same time, resetting it to normal operation just like rebooting your computer.

I actually knocked myself unconscious and rebooted my heart at the same time when I was 22 years old. I was holding the chassis of a tube amp (an SVT bass head) with my left hand, and poking around the 600-volt DC supply with a screwdriver held in my right hand. My hand slipped and contacted the shaft of the screwdriver while it was touching a big capacitor, and I can remember my arm flying up over my head and blacking out. I woke up laying in the corner after an unknown amount of time, and I'm pretty sure that if this would have been a 600 volt AC shock I would probably have died. But since it was a 600 volt DC shock, I stopped and restarted my heart at the same time. Just dumb luck I wasn't killed, but I gained a healthy respect for electricity after that incident.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 20, 2015, 07:34:59 pm
One step forward one step back...

The mosfet footprint is wrong and I think I built that footprint from scratch so if it's wrong, I did it.  :'(

The mosfet is the black thing about the size of hungry wood tick in the picture.

Over 20 discrete parts on that tiny PCB , I'm too old to hand pop SMD...

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on August 21, 2015, 02:54:45 am
But since it was a 600 volt DC shock, I stopped and restarted my heart at the same time

Are you sure about that?!  This reminds me of all of those silly TV programmes which show a defibrillator being used to start a stopped heart... That's not what they're for and they can't do that.  I have a son who is a trainee paramedic who points out these things.

Over 20 discrete parts on that tiny PCB , I'm too old to hand pop SMD...
Does your Chinese PCB vendor not offer a population service?  If not, you should easily be able to find a company who can supply built PCBs.

Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 21, 2015, 09:57:39 am

Does your Chinese PCB vendor not offer a population service?  If not, you should easily be able to find a company who can supply built PCBs.

Steve.
While prototypes are getting more accurate, I need to prove that the design is correct before I even think about having some built, and as I mentioned the mosfet footprint is wrong so back to the drawing board...

I would use a US contract manufacturer "IF" I were to build any number of these, but those guys don't want to turn on the machines for less than 250 units or more. I am apprehensive about getting into that business (would need UL and more) .

 For now I need to confirm that this works (if I can connect the mosfet to the wrong pad spacing). It's hard enough with a good pad layout.

JR

PS: I suspect the defibrillator is used to stop fibrillation.  :o  Kind of like reseting the heart to override the ineffective, too-fast heart rate, so a natural rhythm can take over again. It is a TV cliche to restart a stopped heart, kind like the way that every PA system on TV makes feedback.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on August 21, 2015, 12:58:12 pm
There are folks around these parts who will hand build 10 of something.  And you can often find someone at a CM who will do piece work at home.  Solectron got in big trouble a few years ago for doing too much of this.  It was one thing for supervisors to give some prototypes to people to build at home instead of firing up the lines, it was another when they were doing production work for major customers.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 21, 2015, 01:10:40 pm
There are folks around these parts who will hand build 10 of something.  And you can often find someone at a CM who will do piece work at home.  Solectron got in big trouble a few years ago for doing too much of this.  It was one thing for supervisors to give some prototypes to people to build at home instead of firing up the lines, it was another when they were doing production work for major customers.
Yes I know of some guys doing their own hand pops (over on the DIY forum)... I might get them to do a few for me but I'd probably need to order a stencil (I didn't).

We'll see,,,It turns out I made the mosfet footprint leads on a 1mm pitch when the part is actually 1.5mm pitch so that's awkward to put it kindly. If I can cheat it I might build one or two to prove out the part values. and maybe get a real company interested.  ;D

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 21, 2015, 02:57:36 pm
We have lights and action.

This is the light show for my intentional RPBG test outlet..

The far left green LED indicates ground present (it can't tell bootleg from real ground)
The next green LED for line hot is dark.
The red LED for ground hot is on... ;D (danger Will Robinson)
The yellow LED for neutral hot is also on. (warning)

It works..... 8)  If I plug it into my bench outlet I get just the single yellow LED because that outlet is swapped line-neutral and lacks a ground. Testing other outlets around my house I get mostly single green for line hot, open ground.

I think it's a mistake to have the ground LED next to the line, since it will be harder to see than if they are spread apart. Especially inside the plastic housing. I can swap the green line LEDs with the Yellow neutral LEDs then swap line and neutral input to get a better order. Then it would be green (ground, present) yellow(neutral hot), red (ground hot), and green (line hot). So green are the two outside LEDs.  The ground LED is not in the same line with the others but everything is so tight you can't see that small difference.

I had one open connection and one solder bridge on the board... not bad for a tired old man hand-popping tight SMD.

I need to see how hard it is to cheat the mosfets into the incorrect foot print, might build a couple more (but not 24 of them).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on August 21, 2015, 05:51:52 pm

We have lights and action.



In the context of a concurrent thread this intro gave me pause..

Maybe a bit a light at the end  if the tunnel it seems! 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 23, 2015, 12:10:20 pm
Got a chance to do some field testing and with the plastic cover the green ground present LED, right next to the green line good LED makes it harder to see the line LED.  I will definitely swap the line with neutral so greens are the two outside LEDs.

I tested my next door neighbor's garage/workshop (that he wired himself). He seemed a little nervous while I tested, but every outlet tested good, grounds present and green for line hot. :-)

I do not love the clear plug package..diffuses the LED light too much. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 25, 2015, 03:16:01 pm
Good news bad news.

Bad news first... The clear plug housing is not opaque enough when plug is oriented upside down and I have to look at the bottom LEDs through the thick housing. To hard to see in bright daylight (at a different neighbors house).  :'( So back to the drawing board for a prototype package.

Good news. I have just determined that I can reliably solder to the too-tight MOSFET footprint by not soldering the middle pin that is also connected to the tab, by soldering just the tab and two outside pins, no solder bridges.  ;D These proto boards are all usable... while hand popping tiny SMD parts may not be the best use of my time, but I'm too cheap to pay somebody for onsey-twosey builds.

I may put out a few units for more beta testing... I can just solder these to a short line cord for that. I may make beta testers sign a statement that they will hold me harmless if they use these in their bathtub.

JR   

PS: While we're talking any suggestions for who i could partner with to merchandise these? I don't think GE who sells the cheap hardwares store version would be interested.  8) I figure a couple $10k for UL listing, another $10-20k for tooling slick packaging. Should be relatively cheap to build in production quantity. Should be a large niche market for informed customers.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on August 25, 2015, 04:10:09 pm
PS: While we're talking any suggestions for who i could partner with to merchandise these? I don't think GE who sells the cheap hardwares store version would be interested.  8) I figure a couple $10k for UL listing, another $10-20k for tooling slick packaging. Should be relatively cheap to build in production quantity. Should be a large niche market for informed customers.

I can't help you with PCB assembly or merchandising, but for the package tooling, my brother-in-law works for a custom injection mold (mould, if you're from the UK) manufacturer that also does prototype, short- and long-production runs as well as in-house engineering and design services.  http://pilleraimmco.com/
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 25, 2015, 05:15:41 pm
I can't help you with PCB assembly or merchandising, but for the package tooling, my brother-in-law works for a custom injection mold (mould, if you're from the UK) manufacturer that also does prototype, short- and long-production runs as well as in-house engineering and design services.  http://pilleraimmco.com/
It's not that i can't I just don't want to do it... I have 3-D cad design software on one of my PCs and actually designed the injection molded case for my drum tuner..  A two-part front back clamshell that nests together. I designed it and had the injection molding tool base machined in China  (Your brother in law's company probably farms out their tooling overseas too..) It is a lot cheaper than using machinists in the west.
(https://www.resotune.com/new_splash.jpg)

This outlet tester would be a smaller/simpler package than I already did, but even better is to partner with somebody that already has something similar tooled up. It would be sweet to drop my circuit into that cheap outlet tester package.

But at this point I don't want to spend a few $10k of my own money, and develop another new product. I need a partner who can take this and run with it. I already did the hard part.  8)

While i don't underestimate the value of good execution.

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on August 26, 2015, 02:20:28 am
It's not that i can't I just don't want to do it... I have 3-D cad design software on one of my PCs and actually designed the injection molded case for my drum tuner..  A two-part front back clamshell that nests together. I designed it and had the injection molding tool base machined in China  (Your brother in law's company probably farms out their tooling overseas too..) It is a lot cheaper than using machinists in the west.

An understandable assumption, but they actually do the tooling in-house in their Woodland, Washington facility, and part production runs in a nearby facility. They have built molds for many well-known companies from athletics to aerospace and many other industries. My BIL says that they've had to repair some Chinese-made molds, and that the molds from China are getting better (but still not up to their standards ;) ). Many of their molds get sent to China by their customers for production. Their business has been growing, so that's a good sign. It's always nice to see an onshore shop doing well.

They may not be able to compete on price, but they are very competitive with tooling quality, customer service, lead time, and turnaround time. If you can ramp up production a month earlier, that can mean a significant revenue boost that easily pays for the higher cost of onshore machining.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 26, 2015, 06:31:40 pm
An understandable assumption, but they actually do the tooling in-house in their Woodland, Washington facility, and part production runs in a nearby facility. They have built molds for many well-known companies from athletics to aerospace and many other industries. My BIL says that they've had to repair some Chinese-made molds, and that the molds from China are getting better (but still not up to their standards ;) ). Many of their molds get sent to China by their customers for production. Their business has been growing, so that's a good sign. It's always nice to see an onshore shop doing well.
I know just enough about injection molding to know that mold design involves a lot of experience. I worked with a plastic pusher in TX, who took my part design and spec'd out a mold to be made with a different partner in China (i think he quoted with 3 vendors). I worked out all the draft angles so part was actually manufacturable, but the TX guy worked out the runners and gates to make the part not suck.

I had some fun and games with translation errors between my 3D cad format and the 3D cad format the Chinese were using, but we made a couple SLA (?) parts or whatever they used to call the 3D printer prototypes before they were so commonplace, to prove we were on the same page. A test push through the tool in China proved it was really OK..

We then shipped my tool back to TX to push plastic here. 
Quote
They may not be able to compete on price, but they are very competitive with tooling quality, customer service, lead time, and turnaround time. If you can ramp up production a month earlier, that can mean a significant revenue boost that easily pays for the higher cost of onshore machining.

I have no doubt that US tool quality would be excellent. Being able to communicate in English is certainly a plus. It was not an accident that I used a middle man for the nuts and bolts communication with the Chinese vendor. I will need to think about how valuable a US made tool might be. I am not pushing plastic domestically because it is cheap but for the control with my low volume product. The cost nut for my injection molding project was the tool not the parts.

If I was a high volume cost sensitive manufacturer, I'd probably push plastic and assemble the product completely in China. When I visited contract manufacturers in China for Peavey back last century, one of the facilities I visited was a huge plastic operation. They made plastic parts for all kinds of appliances like computer printers, etc. They had two huge NC milling machines for making molds, and a room full of geeks on PCs tweaking 3D designs.  Of course there is a continuum of high/low quality operation in China so it is hard to make sweeping generalizations. Working with a US vendor should be safer.

JR

PS: I assembled 4 more boards today... this is definitely not fun... :o  It took me an hour and a half just to pop the diodes ( 5 per board) they are tiny and have polarity... I needed three layers of magnifying lenses just to see the cathode marking. These units are definitely not for sale, but I will give away bare PCBs to anybody crazy enough.  ;D ;D
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on August 27, 2015, 05:52:52 am
It is a TV cliche to restart a stopped heart, kind like the way that every PA system on TV makes feedback.
Yes.  And on The Simpsons it's always the same feedback sound effect every time someone walks up to a microphone!


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 27, 2015, 10:36:23 am
Tweaking and testing my outlet tester I have found a new issue. My ground present LED is too sensitive. Testing around my house I have found a few outlets where stray ground leakage is enough to get a visible ground LED reading. I am confident these outlets are not grounded (none are in my house). When I follow-up test with a neon lamp probe, that indicates a ground present too, so enough leakage for neon lamp (low mA?).

I could apply some circuit design magic and require a higher current threshold before I light the ground present LED, but that could cause a different problem. If I increase the total ground LED current test, this will trip GFCI protected outlets. The ground present LED current is pulled from line or neutral and flowing into ground, so not returning through the GFCI loop.   :'(

In my judgement that would be undesirable since the outlet GFCI turning off the outlet will make it impossible to test for polarity or hazards.  ;D

So options look like:

1- Keep the design as is, that may give some false true ground present readings.

2- Lose the ground present reading- while still testing ground for dangerous voltage. (How important is ground present?)

3- add a ground test switch, running at higher current. This would also double as a GFCI trip test switch, since making the current threshold high enough to ignore possible leakage would also trip GFCI (5mA threshold).

I will keep thinking about a way to finesse this but right now the ground present is not as reliable as I hoped. FWIW testing those same outlets with the cheap hardware store tester gives all kinds of bogus readings. I suspect no ground test might be better than an unreliable reading.

What do you guys think?

JR

PS: that cheap outlet tester is looking worse and worse the more I try it...

Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on August 27, 2015, 10:03:45 pm
I like the GFCI test button-I have a standard 3 light tester with a test switch -which doesn't work when there is no ground present.  I would think that would eliminate bogus testing. 

How important is a ground?  If a device needs a ground pin to be UL listed, I would think very-that is the first line of defense safety wise.  Unless the circuit is GFCI protected.  If you run a bunch of LED lights off an edison receptacle without a ground and something shorts to your truss you have just created a major hazard!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 28, 2015, 02:18:16 pm
I like the GFCI test button-I have a standard 3 light tester with a test switch -which doesn't work when there is no ground present.  I would think that would eliminate bogus testing. 

I don't like the added complexity but if I make it an optional push button it will allow testing GFCI protected outlets without false readings and unwanted trips.
Quote

How important is a ground?  If a device needs a ground pin to be UL listed, I would think very-that is the first line of defense safety wise.  Unless the circuit is GFCI protected.  If you run a bunch of LED lights off an edison receptacle without a ground and something shorts to your truss you have just created a major hazard!

Grounds are indeed very useful as we cannot ASSume that everything is RCD/GFCI protected. Looking around my house, outlet grounds are pretty scarce. I wouldn't be surprised if there are similar flawed cases of DIY wiring in bars and less professional venues.

For that reason if my tester has a ground test function it needs to be reliable. I figure it will take something like 20 mA to  completely swamp out stray leakage paths.

This adds yet another concern as an outlet with a floating ground, with 20 mA dumped into that ground will energize any chassis plugged into that outlet. That is a motivation to keep that test current < 10 mA.   This may still end up slightly compromised but you should be able to see a strong vs weak ground from the LED intensity.
====
I looked at small power transformers to pull current that wouldn't trip a GFCI and at low secondary voltage would not be a shock risk to humans from energized floating chassis grounds (6.3v is a popular transformer). I found some nice PC mount transformers but none for sale in small quantity.  :'(

A little more exotic option I could whip up a HF switcher so a tiny HF transformer could make a few mA of isolated current. While I need to think about this, I could leave this chopped DC output unfiltered and perhaps impute some information about the inductance of the ground run. Of course this opens up the different can of worms about RF emissions.  :'(

Interesting.. I may do some more testing to see if 10 mA can reliably ignore my leaky outlet grounds. Some are actually appliance related, since my kitchen outlet does not give me the false reading if I unplug the kitchen outlet strip.  IIRC my
kitchenaide mixer is one of the kitchen ground leakage offenders.

But the bathroom outlet has no such appliances and still gives me a false ground present??
 

Interesting, but if this was easy it would already be handled.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on August 29, 2015, 12:15:58 pm
Maybe a crazy thought-but could you put say a 50V MOV across the ground/neutral to prevent the voltage from going a full 120 volts if the ground was in fact open?  I haven't played with them much so not sure of all the implications.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 29, 2015, 12:21:16 pm
Maybe a crazy thought-but could you put say a 50V MOV across the ground/neutral to prevent the voltage from going a full 120 volts if the ground was in fact open?  I haven't played with them much so not sure of all the implications.
That would pretty much be the same as a bootleg ground so dangerous if neutral fails open back to the panel. While it might put less voltage on the chassis in such an open neutral condition still undesirable. IMO

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 29, 2015, 01:24:40 pm
I am making progress on getting a more reliable ground present indication without increasing current enough to trip the GFCI.. So far it works on my kitchen outlet that previously gave a false.  Still getting a false in the bathroom, that isn't logical so I may have to look more closely at that outlet.

Using my VOM with floating ground I coincidentally measure the exact same voltage on both the neutral and ground pin... Since i don't believe in coincidences when it comes to electricity I suspect very strongly that there is an accidental bootleg ground in that outlet. As i recall the GFCI outlet was a very tight fit in the junction box, so neutral touching the metal box could perform the bootleg.   :o  My other leaky outlet shows 4V between neutral and ground using the same floating measurements.

So I suspect I have nailed the "false" ground present indication,  ;D and have something else to fix about my home wiring.  :'(

JR

PS: I have decided to stop publishing design refinements until I find someone to license this too,,  If i keep giving away the milk, I'll never sell the cow.  This ground fix is a few more cheap components but nothing major.  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on August 29, 2015, 03:54:03 pm
Maybe a crazy thought-but could you put say a 50V MOV across the ground/neutral to prevent the voltage from going a full 120 volts if the ground was in fact open?  I haven't played with them much so not sure of all the implications.

The problem would become huge if you plugged into a receptacle with swapped hot and neutral wires. Now your 50-volt MOV would be connected between the hot and EGC. If the rectacleep had a proper ground it would short and trip the main circuit breaker. If it had an open ground, now the chassis of the gear would be tied to the incoming hot wire. In either case it would be very bad indeed.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 30, 2015, 06:17:03 pm
Kind of bizarre but I today dug into my bathroom outlet and found the accidental bootleg to neutral... I probably need to buy a new larger junction box. There was not enough clearance to wedge even a 1/16th inch thick piece of fiberglass PC stock into both sides. One fit but not two. I did put some tape over both the line and neutral screws, while they are recessed and should not have shorted to the junction box.

Now even my original outlet tester correctly registers that outlet ground as open circuit. So it looks like my testers correctly identified a ground path where they shouldn't have been one.  :o :o

JR

PS: I only have 8 fuses in my service panel, and this outlet was on the 7th fuse I tried.  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on August 30, 2015, 10:18:37 pm
Kind of bizarre but I today dug into my bathroom outlet and found the accidental bootleg to neutral... I probably need to buy a new larger junction box. There was not enough clearance to wedge even a 1/16th inch thick piece of fiberglass PC stock into both sides. One fit but not two. I did put some tape over both the line and neutral screws, while they are recessed and should not have shorted to the junction box.

Now even my original outlet tester correctly registers that outlet ground as open circuit. So it looks like my testers correctly identified a ground path where they shouldn't have been one.  :o :o

JR

PS: I only have 8 fuses in my service panel, and this outlet was on the 7th fuse I tried.  8)

Off topic, but I have always been OK with fuses-generally more reliable than breakers.  However, I have started running into fuse holders in older resi fuse boxes where the fiber insulator has or is disintegrating-effectively shorting out and bypassing the fuse.  I am starting to to view even properly sized edison fuses with suspicion.

Back on topic-congratulations on finding a difficult issue that would usually go completely undetected.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on August 31, 2015, 12:11:27 am
Off topic, but I have always been OK with fuses-generally more reliable than breakers.  However, I have started running into fuse holders in older resi fuse boxes where the fiber insulator has or is disintegrating-effectively shorting out and bypassing the fuse.  I am starting to to view even properly sized edison fuses with suspicion.

Some of the really old fuse holders had mica insulators. I think that mica probably outlasts the fiber by a long shot, as long as it's protected from physical abuse.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on August 31, 2015, 12:13:00 am
I am making progress on getting a more reliable ground present indication without increasing current enough to trip the GFCI.. So far it works on my kitchen outlet that previously gave a false.  Still getting a false in the bathroom, that isn't logical so I may have to look more closely at that outlet.

Using my VOM with floating ground I coincidentally measure the exact same voltage on both the neutral and ground pin... Since i don't believe in coincidences when it comes to electricity I suspect very strongly that there is an accidental bootleg ground in that outlet. As i recall the GFCI outlet was a very tight fit in the junction box, so neutral touching the metal box could perform the bootleg.   :o  My other leaky outlet shows 4V between neutral and ground using the same floating measurements.

So I suspect I have nailed the "false" ground present indication,  ;D and have something else to fix about my home wiring.  :'(

Do I read correctly that you *thought* you were getting a false positive, when in fact your device was indicating a problem? Just goes to show the value of making assumptions!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 31, 2015, 09:35:32 am
Do I read correctly that you *thought* you were getting a false positive, when in fact your device was indicating a problem? Just goes to show the value of making assumptions!

It shows the value of testing outlets. The actual false on my kitchen outlet with the prior test circuit made me less trusting, but finding the bootleg path in my bathroom confirmed that my tester was right, and the outlet wrong.

Now all are in harmony and my outlet tester can successfully ignore the stray leakage at least around my house..

 JR



 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on September 06, 2015, 06:07:59 pm
Getting ready to pull the trigger on rev B (still some clean up to do. I noticed my small diode footprint wasn't correct either. ).

I fixed the too-sensitive ground present LED and some ghosting (leakage) into LEDs.

I completely rearranged the PCB so now the display LEDs are all on the bottom of the PCB and should be visible through the line cord hole in typical plugs.

I added several parts but kept the PCB the same size so it's a tight house.

I added one more LED (yellow) for power present. So when you plug in you always get at least the yellow LED. If it detects a good ground the green lights too.

Like before there are three more LEDs that light selectively when the probe is touched.

Green for line is hot.
Yellow for neutral is hot
or Red for ground is hot.

RPBG lights up the yellow and red hot LEDs.

Debating whether to take the 3 week slow boat (air mail)  shipping deal.

Progress

JR

[edit- new boards on order-- 9-9-2015 this time I paid and extra $9 for shipping from singapore instead of free from Hong Kong... we'll see if the premium is worth it... I'm too cheap to pay $33 dhl shipping for $14 worth of PCB. HK took about 3 weeks.   /edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on September 09, 2015, 05:44:17 pm
crude proof image

boards on order


JR

[edit] arrived today, so exactly 3 weeks.[/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 05, 2015, 08:46:28 pm
The eagle has landed...

I has to steal some blue LEDs from a broken dishwasher control board to pop these...

Both pix are of my intentional RPBG test outlet.

First picture with no finger touch is Blue LED and Green LED indication power and ground present... Unfortunately it does not perceive that ground is hot, just that something it is connected.

Second picture is the near full light show. Blue and green for power and ground present, then red and yellow LEDs for RPBG

All other wiring configurations test accurately...

My ground fix no longer gives a false good ground for my one kitchen outlet with leaky impedances on the open ground (from several kitchen appliances), but I now I do get a very dim red on just that one outlet with a leaky ground. Such a conflicting dim indication when ground registers as open should be ignored but I'll keep chewing on this...

So good progress,,, Sorry about the photos but a lot of light in a tight space. The blue is kind of bright so I need to tone that down some,,but I need to see what my actual blue LEDs look like... they are due in any day now.

JR

Note: that standard tester plugged in the other hole is saying all OK for the RPBG outlets.  :o
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 07, 2015, 11:48:07 am
I swapped out the blue LEDs and they are still too bright so I need to tweak some more resistor values, not trivial with tiny SMD parts... I need to order some more values.

Everything works great and I tamed my false ground readings, but now that one leaky ground outlet is causing dim indications on ground and neutral hot LEDs. I am pretty sure I can squelch that with different resistor values while it will take more field testing to find any other quirks. 

For now if the ground LED indicates floating/open ground we should question spurious dim readings elsewhere... I think I just need to lower the impedances around this, and lower the current driving the blue LED.. the blue color is so intense it almost makes my green LED look yellow.

A commercial product needs to be bigger and LEDs spaced further apart. But this prototype stage is just proving out the circuit design, not a production product design.

JR

[edit] I just tested with a different value resistor and I can kill that last weak leakage, now I just need to wait for some proper SMD resistors (I tested with a huge thru hole part). So probably later this week.  ;D ;D ;D ;D  [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: Jordan Wolf on October 07, 2015, 01:36:07 pm
JR,

It looks great! I've been [silently] following this thread just to see what progress has been like; I haven't encountered too many improperly-wired outlets, but this little gizmo might make me even more certain of that.

Very much looking forward to the finished product.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 07, 2015, 01:44:02 pm
I am talking to a company to possibly partner on this and the stinger GFCI power drop. They are already in the business and could use their existing tooling with minor modification. They also have experience dealing with UL.

I just need to be very careful about the NIH philosophy. I used to be the guy who evaluated outside technology at my last day job and I gonged every single idea i reviewed, so I need to be sensitive to that.   8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on October 08, 2015, 12:25:29 am
For the truly discerning guitar player you could sell a premium version with platinum alloy contacts guaranteed to be sonically transparent.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on October 08, 2015, 01:53:07 am
For the truly discerning guitar player you could sell a premium version with platinum alloy contacts guaranteed to be sonically transparent.

It will also need a mica circuit board and a marble or Rosewood case to truly be audiophile quality.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on October 08, 2015, 02:22:16 am
It will also need a mica circuit board and a marble or Rosewood case to truly be audiophile quality.


Oh no. No, no, no.  Lets not let this particular "discussion" degrade into audiophoolery, please! 
JR's got something REAL and USEFUL here.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on October 08, 2015, 04:12:38 pm
I'm a beta tester for JR. It turns out that my entire dwelling (such as it is) has RPBG on the receptacles that are NEMA 5-15 (not to mention the 1-15 receptacles).  Plug-in GFCIs for me!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 08, 2015, 05:15:35 pm
I'm a beta tester for JR. It turns out that my entire dwelling (such as it is) has RPBG on the receptacles that are NEMA 5-15 (not to mention the 1-15 receptacles).  Plug-in GFCIs for me!

It is not clear what is going on at Mark's house, unless he did more testing since we last spoke.

The red LED should not light ever unless you are touching the probe. I have seen some dim red LED leakage when plugged into my RPBG test outlet.

When you touch the probe with RPBG you will get red, yellow. and green (ground) LEDs.

Please follow up with VOM or Neon lamp probe as I suggested.

I'll get you a second generation tester soon... I'd be careful around those outlets, until confirmed good, or fixed.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on October 08, 2015, 08:27:53 pm
I'm a beta tester for JR. It turns out that my entire dwelling (such as it is) has RPBG on the receptacles that are NEMA 5-15 (not to mention the 1-15 receptacles).  Plug-in GFCIs for me!
Here's an article I wrote on how to test for RPBG outlets manually with a meter and a NCVT. Best to double-check: http://ecmweb.com/contractor/failures-outlet-testing-exposed
 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on October 08, 2015, 10:38:25 pm
From my experience most homes that have 1-15 receptacles still have 2 wire either  K & T or  Romex.  Bootleg grounds are common, as is reverse polarity. As Mike has repeatedly warned this can be a dangerous combination.

The other thing that might be creating odd readings on JR,s beta device could be the lack of a grounding electrode and or bonding.  This could cause the neutral to appear to be at any potential with respect to ground and other metal objects/systems.  Not sure how a body's capacitance would play out as far as grounding if the only true reference is hundreds of feet away?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 08, 2015, 11:26:13 pm
From my experience most homes that have 1-15 receptacles still have 2 wire either  K & T or  Romex.  Bootleg grounds are common, as is reverse polarity. As Mike has repeatedly warned this can be a dangerous combination.

The other thing that might be creating odd readings on JR,s beta device could be the lack of a grounding electrode and or bonding.  This could cause the neutral to appear to be at any potential with respect to ground and other metal objects/systems.  Not sure how a body's capacitance would play out as far as grounding if the only true reference is hundreds of feet away?
The secret sauce for my tester is to use the human body as a local 0V reference. Of course nothing is exactly 0V but close enough.(+/-10V?) I buffer that human voltage reference with a high input impedance MOSFET. 

AFAIK the design is getting mature and works as expected everywhere I have tested it so far (perhaps a half dozen different buildings).

The results Mark reported made me concerned the prototype was faulty... (hand soldered by an old man), but when I got it back it worked exactly like it did when it left.

I'll get him a second generation prototype that has some minor improvements, less spurious leakages..more robust ground present indication etc. If he still gets spurious results I will ask him to do more testing of his power.

I fell like this tester design is getting pretty close to ready for prime time... The final resistor values I need to finish tweaking this are ordered and shipped so just a matter of days.  ;D

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Rob Spence on October 08, 2015, 11:28:53 pm
Neat!

I want one.


Sent from my iPad using Tapatalk HD
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on October 09, 2015, 01:11:29 am
Update:  Follow-up testing (using a Fluke 323 clamp meter w/probes and Fluke 1AC-C NCVT) show that the NEMA 5-15 receptacles do NOT appear to have a RPBG condition. Tested as per Mike's link (above).

I'll repeat the tests this weekend to check my work.  I'll also check using two other NCVTs I have, and a different DMM, and report back.

Edit:  Pending additional testing, the above results should probably be qualified as "initial" or "preliminary". I think that I know how to conduct the testing, but I don't want to assume too much, or rely on a single result with only one set of test instruments.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 09, 2015, 09:48:53 am
I also like neon lamp probes, or using a VOM with the body serving as the ground reference but BE CAREFUL to make sure VOM is in AC Volts scale, since using ohms or current scale could deliver a dangerous shock hazard.

My NCVT is useless for determining outlet wiring (too sensitive). It goes off when I get anywhere near my bench with it.

JR

PS: Using my trusty old ratshack VOM, and JR_as_ground I measure 50 VAC on line, 11 VAC on neutral, and 1 VAC on an open floating ground. Not very precise but good enough to differentiate line from neutral. Just be careful when probing hot power circuits.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on October 09, 2015, 10:42:17 am
I also like neon lamp probes, or using a VOM with the body serving as the ground reference but BE CAREFUL to make sure VOM is in AC Volts scale, since using ohms or current scale could deliver a dangerous shock hazard.

My NCVT is useless for determining outlet wiring (too sensitive). It goes off when I get anywhere near my bench with it.

JR

PS: Using my trusty old ratshack VOM, and JR_as_ground I measure 50 VAC on line, 11 VAC on neutral, and 1 VAC on an open floating ground. Not very precise but good enough to differentiate line from neutral. Just be careful when probing hot power circuits.

Sounds like a test for Darwin Award (http://www.darwinawards.com/) nominees.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on October 09, 2015, 10:58:13 am
Neat!

I want one.


Sent from my iPad using Tapatalk HD


I'm with you!  Been a big cheerleader of this project from the start - and am thrilled that JR is in discussions with a manufacturer.
One way or the other, I REALLY want one, too!
frĺnk
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 09, 2015, 12:17:13 pm
Got my new resistors in today, so this weekend I should be able to finalize this.

Slow and steady but moving forward...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on October 09, 2015, 12:44:08 pm
Edit:  Pending additional testing, the above results should probably be qualified as "initial" or "preliminary". I think that I know how to conduct the testing, but I don't want to assume too much, or rely on a single result with only one set of test instruments.

The  Gold Standard test is to run a long wire to the frame-ground of the service panel, and use a low-impedance meter between it and the Line, Neutral, and EGC-Ground contacts in each receptacle. I also do some loading between the various lines with a 100-watt bulb to make sure there's no open line that's being "phantom" energized via capacitive coupling.

BTW: If you use enough of a load (I have a little 600/1,200 watt space heater for this) you can also figure out if there's a swapped neutral and ground in an outlet. While a swapped N-G won't show up with any standard (unloaded) test, it does create all sorts of ground loop hum in sound systems. I've found swapped N-G lines in several church installs during the last two years of looking, but I was only looking because of a reported ground loop hum. It may be fairly common in new installs done by non-electricians. Another fail that a 3-light tester won't find, and JR's gadget won't find it either.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 09, 2015, 01:39:53 pm
Yup I only confirm that a ground connection is present and then test for hazardous voltages. My tester even says RPBG ground is present,,, but it also warns that the safety ground happens to be hot.  >:( (danger Will Robinson)

I believe I could come up with a microprocessor based outlet tester that could parse out ground quality too, but first things first. A simple outlet tester that accurately reports hazardous voltages seems a useful start and the far more important need.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on October 09, 2015, 01:55:50 pm
Anytime you are getting odd readings, I would strongly recommend verifying the G-N bond in the panel.  That is one of the most common problems I run across. Rarely noted by home inspectors, and often found even when a ground is run.  If the green bonding screw is not installed on a panel, and the neutral bar is used for grounds and neutral you wind up with a situtation where the panel enclosure itself is not grounded-I recently ran into that situation and the CATV installer had "grounded" to the enclosure.

I agree with your focus, JR.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on October 09, 2015, 04:51:51 pm
I believe I could come up with a microprocessor based outlet tester that could parse out ground quality too, but first things first. A simple outlet tester that accurately reports hazardous voltages seems a useful start and the far more important need.

JR

Yes, I would agree that finding hot grounds is the most important thing from a safety standpoint. Sorting out all other possible receptacle mis-wiring condition is rather complicated, but certainly possible with a microprocessor and clever enough programming. JR's design should save lives, and that's the important thing.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 09, 2015, 05:49:29 pm
Yes, I would agree that finding hot grounds is the most important thing from a safety standpoint. Sorting out all other possible receptacle mis-wiring condition is rather complicated, but certainly possible with a microprocessor and clever enough programming. JR's design should save lives, and that's the important thing.
kool...

I just finished swapping out the leakage damping resistors with lower values in two boards and both work perfectly, even on my very leaky ground kitchen appliances outlet with no more dim false indications.

Now blue LED always on to indicate power present (useful to determine if outlet is energized).
Green LED on without touching probe if ground connection present, dark if no ground, with no more false dim indications from stray impedance.

When you touch the probe the Green Line LED lights if line is hot.
Yellow Neutral LED lights if Neutral is hot.
Yellow and red LEDs light for RPBG...

Now it's time to get serious.  8) 8) 8)

JR 

PS: I'll send a new improved tester to Mark next week and we'll get him sorted.

PPS: 32 smd parts on each tiny board, I don't think I'll build a lot of these myself.  ::)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 09, 2015, 07:15:49 pm
OK this is getting interesting... I found another outlet on an old outlet strip , all plugged into that same problem kitchen outlet, that is even worse.

This outlet strip literally daisy chains through two other outlet strips on the way to the wall outlet. I am now seeing some symptoms like what Mark reported. This very old outlet strip with individual switches for each outlet lights up the green ground LED WHEN SWITCHED OFF??? 

This outlet is fed with proper line hot power, and the switch is breaking the line connection.

It clearly looks like floating grounds can cause issues...   

No problemo... If I can reproduce it, I can squash it.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 10, 2015, 12:01:48 pm
OK, I have my outlet tester working cleanly now, even on the new worst case leaky ground outlet.

I can't guarantee that there isn't some even worse noisy/leaky ground out there, but the spurious leaks do not interfere with the serious business of detecting outlet hot pins for now. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 11, 2015, 07:19:44 pm
I have three outlet testers dialed in and assembled (into three different plug housings). Two of the three don't look bad.  ???

Mark: yours will be in the mail tomorrow. Yours is the best looking of the group.

One will get sent to my possible corporate partner... and the runt (ugly) one will be mine.

I am figuring out more about the false readings. The switched outlet with line floating provided stray paths for the noisy also floating ground that could alternately light the ground LED, and even indicate ground hot LED when the probe was touched. This was while only the neutral was actually connected.  :o  Open ground "and" open line is not remotely a typical test scenario, but since I've added more damping even my new problem outlet is quiet (dark when it should be). 

I expect I will learn even more from ongoing beta testing but looking good now on all my local (and neighbors) test outlets.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on October 11, 2015, 08:01:53 pm
Very cool, JR. Thank you for sending me the pretty one. I look forward to carrying it around with me and checking random receptacles out and about.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on October 31, 2015, 11:44:33 am
i showed a pic of JR's advanced outlet tester at AES today, and the concept was well received. But several attendees came up after the presentation and asked where they could buy one. So?????

I moved this response back into my tester thread to keep this discussion in one place.

Thanks Mike for the good feedback. I am confident there is a market for this. Making money while doing it is another matter.

"In for a penny in for a pound", I just purchased the UL spec so I am now $400.00 lighter.  :'(

The good news this clears up a few unanswered questions. It's illegal for me to reprint the spec but I can paraphrase (I think?).

**At first glance the spacing (3/64") does not appear to preclude using the small PCB format I used for my prototypes... I only get a half dozen warnings from the design rules check, but need to look closer, some of these component footprints look smaller than the UL spacing.

** leakage/insulation resistance. This seems pretty strict (100MOhm tested at 500V). I can buy 100M surface mount resistors but they are not as cheap as normal values, but not killer ($0.08 in high quantity). I need to buy some samples and test...  Gate leakage worst case 100 nA times 100Mohm input R sounds like a recipe for false indication. But I need to test to see how it works first, before I lobby for lower insulation R. Many UL specs seem to tolerate less than 100M insulation (around 1uA leakage 120V/100MOhm).

*** they list 4 conditions associated with outlet wiring to indicate presence or absence of. I would love to post this short list to get some help deciphering. The words are english, but it reads like a bad translation (from chinese?). I'll ask Mike for help off list.  The 25 page spec has lots of info about GFCI and AFCi, but weak disclosure about the basic terminology used. 

*** they even spec how much current I can send down the ground to test it I remember reading something like 3mA yesterday but now I can't find it again. (The GFCI test specs >6 but <9mA).

So one more expensive step forward... and setting up a UL file listing is another major expense, but at least now I have a vague roadmap.

JR

PS: They even provide fine print for the instructions sheet (that I don't recall ever seeing with the unit I bought). "does not detect two energized  wires" (my paraphrase)   WTF?????????? I'm guessing this is the RPBG exception.  :-[ :-[ :-[
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 04, 2015, 09:49:45 am
This is one of those funny, political things.  In the USA, the terms grounding and grounded are (confusingly) used to identify the neutral and earth, and there is this thing that they are the same.  In pretty much every other non-110V country, in regulatory terms, the neutral is required to be treated as a "live" conductor, and thus there is no distinction between N/G and N/G, they are both "live" to ground, and both require the use of Y rated caps.  (There is also an X rated cap to go between L and N)

Try Newark for Y rated caps; Newark is now the USA arm of Element 14, formerly known as Farnell Electronics, and they definitely know what a Y cap is.

Last first.... good tip on Newark  (http://www.newark.com/productimages/thumbnail/en_US/4815109.jpg)  I found a 0.15 uF/300V rated Y2, no Y1 caps that large but Y2 is rated for 5000V so should be good enough.  $0.70 so not cheap but not crazy expensive and available. Not small either. 0.15uF passes large enough current to trip the GFCI but small enough current to prevent humans getting stuck to it.
http://www.newark.com/webapp/wcs/stores/servlet/Search?catalogId=15003&langId=-1&storeId=10194&categoryId=800000051502&pageSize=25&beginIndex=1&showResults=true&pf=810066864,812028953 (http://www.newark.com/webapp/wcs/stores/servlet/Search?catalogId=15003&langId=-1&storeId=10194&categoryId=800000051502&pageSize=25&beginIndex=1&showResults=true&pf=810066864,812028953)

Yup I've been trying to make sense of the UL spec for outlet testers and not only do they use "grounded" and "grounding" do describe neutral and safety ground, they also use "ungrounded" to describe the hot lead. Elsewhere they talk about polarity of "line conductors" , I ASSume they mean line (hot) and neutral (0V return) are the line conductors?

I guess this word play with "ground" is how they amuse themselves. The outlet tester spec actually has a glossary but doesn't bother with such basic definitions.

JR

PS: I moved this response to keep the good info together.
Title: Re: brain storm an optimal human safety system for back line
Post by: TJ (Tom) Cornish on November 04, 2015, 10:00:36 am

Yup I've been trying to make sense of the UL spec for outlet testers and not only do they use "grounded" and "grounding" do describe neutral and safety ground, they also use "ungrounded" to describe the hot lead. Elsewhere they talk about polarity of "line conductors" , I ASSume they mean line (hot) and neutral (0V return) are the line conductors?

I guess this word play with "ground" is how they amuse themselves. The outlet tester spec actually has a glossary but doesn't bother with such basic definitions.
They copied it from the NEC which used to read like that.  In more recent versions the NEC abandoned that ridiculous nomenclature in favor of hot, phase, neutral earthed, and a few other words that make more sense most of the time.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 04, 2015, 05:03:16 pm
Old news... After reading the spec I didn't remember seeing instructions with the legally stipulated fine print describing the things that the cheap outlet tester doesn't do. Today I went to the store to maybe buy another tester to check for the legal boilerplate. I didn't have to buy another, the unit comes packaged in plastic attached to a cardboard display card. The very small print describing what they don't do was indeed printed on the back of the counter card so legal to the letter of the UL specification.

Right now I see two problems with the spec... One minor and one harder. The small one is that current leaking to ground is limited to 2mA in the spec. I am using 3 mA now, so I will check but 2 mA may be marginal brightness for the ground present LED. I can finesse this with more circuit complexity, or just use a neon lamp for the ground present that will probably work OK with less than 2 mA.  I will see if there is any flexibility or where the 2mA number came from (perhaps rubber stamping the former neon lamp design).

The more difficult spec to meet is they specify a 100M insulation resistance between hot and any external surface. I might be able to buffer 100M touch input R with the MOSFET but worry that the internal leakage current of a standard MOSFET could lead to unexpected behavior with 100M in series with the gate...

I need to buy some more parts and do more testing before I yank their chain.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on November 04, 2015, 10:55:00 pm
They copied it from the NEC which used to read like that.  In more recent versions the NEC abandoned that ridiculous nomenclature in favor of hot, phase, neutral earthed, and a few other words that make more sense most of the time.

My copy (2014) of the NEC still uses grounded and grounding-I can't find a reference to "neutral earthed"?

I guess I don't understand the confusion-in any given install there are essentially 3 types of conductors.  Current carrying conductors are either "hot" or grounded (or neutral-same function as hot in that it carries current but it happens to be grounded at some point in the system) and then you have grounding conductors which are not intended to carry current except in a fault condition.

But then my perspective is usually from the supply side-not utilization.
Title: Re: brain storm an optimal human safety system for back line
Post by: TJ (Tom) Cornish on November 05, 2015, 06:51:24 am
My copy (2014) of the NEC still uses grounded and grounding-I can't find a reference to "neutral earthed"?

I guess I don't understand the confusion-in any given install there are essentially 3 types of conductors.  Current carrying conductors are either "hot" or grounded (or neutral-same function as hot in that it carries current but it happens to be grounded at some point in the system) and then you have grounding conductors which are not intended to carry current except in a fault condition.

But then my perspective is usually from the supply side-not utilization.
I missed a comma between neutral and earthed.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 05, 2015, 09:59:41 am
I missed a comma between neutral and earthed.
I still think "grounded" and "grounding" invites confusion, the safety ground is surely grounded too, and the grounded line is arguably grounding too. Then we have "ungrounded"? When I hear ungrounded my first thought is not HOT LINE.

I can work ASSuming I understand what they mean. This must be even harder for non english speakers, or otherwise language challenged.  Secret handshakes to learn.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on November 05, 2015, 11:44:27 am
I still think "grounded" and "grounding" invites confusion, the safety ground is surely grounded too, and the grounded line is arguably grounding too. Then we have "ungrounded"? When I hear ungrounded my first thought is not HOT LINE.

I can work ASSuming I understand what they mean. This must be even harder for non english speakers, or otherwise language challenged.  Secret handshakes to learn.

JR

They've called the neutral the "grounded current-carrying conductor".  Yes, it's still kind of confusing to casual readers...
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 06, 2015, 01:50:15 pm
I just ordered some 100M and 150M resistors to see if I can get my outlet tester to pass the 100M insulation test and still work as intended. If this works it will be a lot easier than trying to get them to relax the leakage spec.  8) I currently use a 1M input R but mosfets are extremely high input impedance. The gate-source leakage spec looks like 200M worst case so not a stopper (I think). But this is why we bread board and test stuff.

They test insulation at 500V (with a magneto voltage source) which will exceed the breakdown voltage of my diodes and mosfet, but even if they short it should still pass the insulation test with 100M resistor in series with input. That is still only 5uA so may not be enough current to do any harm to the semiconductors even in avalanche break-down mode.

If I need to I can use higher voltage parts. but first things first. (does it work with 100M input) :o

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on November 06, 2015, 05:43:44 pm
Update:  I am a beta test user for JR's UCT device. I've been carrying it around and checking recepticals at all sorts of locations. So far, the office buildings, airports, and hotels/conference centers I've checked all test as correctly wired.  I see that I should plan a pub crawl to do more "research" at less high end businesses, all in the name of progress, of course!  I'll keep folks advised of further results.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on November 06, 2015, 06:01:29 pm
I see that I should plan a pub crawl to do more "research" at less high end businesses, all in the name of progress, of course!  I'll keep folks advised of further results.

Churches and businesses based in old buildings could make for an interesting data set!
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on November 06, 2015, 07:38:04 pm
Update:  I am a beta test user for JR's UCT device. I've been carrying it around and checking recepticals at all sorts of locations. So far, the office buildings, airports, and hotels/conference centers I've checked all test as correctly wired.  I see that I should plan a pub crawl to do more "research" at less high end businesses, all in the name of progress, of course!  I'll keep folks advised of further results.

Mark, 30 years ago you could have stepped into any place on Last Chance Gulch and found who knows what.

Whatever became of the Iron Front Hotel?
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on November 06, 2015, 08:49:40 pm
Churches and businesses based in old buildings could make for an interesting data set!

Look for old buildings with brand new receptacles. Churches are suspect since may of their stages have been "upgraded" to grounded outlets. That's where the painters and DIY guys do their wiring mischief.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on November 07, 2015, 12:55:15 am
Mark, 30 years ago you could have stepped into any place on Last Chance Gulch and found who knows what.

Whatever became of the Iron Front Hotel?

Tim, I'm pretty sure that is still the case. The Gold Bar and the Western are still there, as is the Rialto. O'Tooles closed a couple of years ago; Rose O'Toole died about two years ago. The Iron Front Hotel is still there; folks are sleeping there tonight.  There is probably less change on the Gulch than you would think (or hope).
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 07, 2015, 09:10:46 am
Look for old buildings with brand new receptacles. Churches are suspect since may of their stages have been "upgraded" to grounded outlets. That's where the painters and DIY guys do their wiring mischief.
Yup churches are target rich environments but they'll probably want you to fix them free.

JR
Title: Re: I hate it when a plan doesn't come together.
Post by: John Roberts {JR} on November 09, 2015, 12:28:22 pm
I just tested with 100M input resistors and the MOSFET buffer doesn't stay turned off... Both line and neutral LEDs glow dimly. Then when I touch the probe the correct LED gets brighter but the wrong LED still doesn't go completely dark.

Which leaves me with two options.

#1 revisit the design to figure out why it is doing what it is doing and see if i can make it work with 100M input Z.

#2 lobby UL to allow <100M insulation between mains and human touch points. I have no doubt that the uAs of leakage from mine are harmless, but that may not matter.

For now I will need to chew on #1 a little more, but it will probably involve more parts and more complexity.

JR

PS: For chuckles I plugged the cheap outlet tester into my kitchen outlet that gave the false hot ground reading before I fixed that. The cheap tester says hot ground, and this is with the leaky mixer unplugged. So false reports a problem that isn't there, while ignoring real problems.  :o
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 09, 2015, 02:53:58 pm
OK Door #1 is still open...

By adding one new part** I have it working again with 100M input Z.  ;D

So if 2mA is acceptable brightness for ground present LED I have met all difficult UL stipulations (AFAIK).

Note: They apparently make a green neon lamp (blue too), so if 2 mA green LED is not bright enough I could use a green neon lamp for that. (I haven't found a source or price yet, but see them around in use).

I have to do one more PCB layout to meet UL spacing requirements but no major changes so I can stick with existing form factor.

I have a couple different replacement plugs on order to determine the best one to repurpose...They are already UL approved so that should simplify my approval. My new plan is to package my PCB inside a currently available plug. So I don't have to tool anything myself besides the PCB.

Another large step forward.  8)

JR


*** as has been my strategy for several months now I have stopped sharing design details  :P

Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on November 09, 2015, 03:29:14 pm
Note: They apparently make a green neon lamp (blue too), so if 2 mA green LED is not bright enough I could use a green neon lamp for that. (I haven't found a source or price yet, but see them around in use).

I think the blue and green neon lamps actually glow orange inside; the bulbs are colored glass. I could be wrong, but that's my understanding. If that's the case, they may not be bright enough for your purposes.

I suppose they could use other gases or impurities to get it to glow different colors, but that might increase the cost of manufacturing by a few cents.

If the bulb is actually clear and the ionized gas glows the proper color, that's probably a benefit.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 09, 2015, 04:34:15 pm
I am not overly enthusiastic about green neon but one of the plugs I ordered has one inside... apparently the normal neon lamp color makes people uncomfortable when coming from inside an electrical plug.  :o

(https://upload.wikimedia.org/wikipedia/commons/thumb/7/7d/NE2COLORED.JPG/220px-NE2COLORED.JPG)

A mixture of neon and krypton (superman?) will glow green, but green is commonly phosphor based (excited by UV)

I am more concerned about cost and availability. Too exotic for me... I don't even like the blue LED.

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 12, 2015, 12:32:23 pm
Found a nice plug to shoe horn my tester PCB into.  Right angle plug with clear housing big old screw head in the middle of the back to serve as the touch probe.

Not cheap, but cheaper than tooling up my own UL approved package.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 18, 2015, 04:39:58 pm
While one of my two beta testers is lost in space, the one who is actually testing outlets with one and reporting back suffered our first field failure.

It took me a while to fix it because I didn't see anything obvious (I expected a broken wire or bad solder connection). I had to carefully set up my bench and scope to look at voltages with the tester plugged in. You don't just fool around with mains voltages, even our puny 120VAC. I eventually found that the MOSFET had gone bad...

My current thinking is 2 possibilities; 1- the mains voltage spiked in excess of the device breakdown voltage, or 2- a static hit to the touch probe. (Door number two is looking good since gate was low impedance to drain <200 ohms).

The good news is I can drop a 50% higher voltage part into the same foot print, and the new improved 100M input network  should reduce stress from external static hits to the touch probe.

I need to figure this stuff out now rather than find out later.

JR

note: there is a zener diode clamp across the gate that in theory should eat any static hit, but it looks like the gate is what broke.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on November 19, 2015, 12:16:55 am
JR, in the event that you succeed in bringing this to market, and I really hope you do, do you have a suggested retail price in mind? Or is it too soon for that? I'd like to commit to buying one if the price is reasonable... but our ideas of "reasonable" might be different. ;-)
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on November 19, 2015, 01:14:59 am
JR, in the event that you succeed in bringing this to market, and I really hope you do, do you have a suggested retail price in mind? Or is it too soon for that? I'd like to commit to buying one if the price is reasonable... but our ideas of "reasonable" might be different. ;-)

Reasonable is a relative term for whatever value is derived from ownership and use.  I see this as a teaching tool that has great practical value and I'd be willing to spend a bit more, perhaps, because of the dual purpose.

How much?  Not sure yet, but I think the home inspector guys would snap these up at $30 - $40.

The market for this device is much greater than our little world.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on November 19, 2015, 01:35:52 am
Reasonable is a relative term for whatever value is derived from ownership and use.  I see this as a teaching tool that has great practical value and I'd be willing to spend a bit more, perhaps, because of the dual purpose.

How much?  Not sure yet, but I think the home inspector guys would snap these up at $30 - $40.

The market for this device is much greater than our little world.


Given an internet price of $12 to $20 for a hospital grade right angle 5-15p device, that $30 to $40 price seems like a pretty fair guess, when produced in quantities that would be sold to the electrical and construction trades.  At more than $50, I would probably hesitate to buy one (as a non-construction industry guy).  NCVTs seem to sell in the $9 to $40 range (depending on brand and quality) at stores in my area, so $30 to $40 seems like a very reasonable price to me.

Please note that I have no inside knowledge of JR's UCT device, and I would not presume to speak for JR. I am a beta tester, but I have no financial interest in the product.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 19, 2015, 10:01:55 am

Given an internet price of $12 to $20 for a hospital grade right angle 5-15p device, that $30 to $40 price seems like a pretty fair guess, when produced in quantities that would be sold to the electrical and construction trades.  At more than $50, I would probably hesitate to buy one (as a non-construction industry guy).  NCVTs seem to sell in the $9 to $40 range (depending on brand and quality) at stores in my area, so $30 to $40 seems like a very reasonable price to me.

Please note that I have no inside knowledge of JR's UCT device, and I would not presume to speak for JR. I am a beta tester, but I have no financial interest in the product.

I have no idea what the price will be... In fact I really don't want to start another business (I'm old and tired), but this is too important not to do, IMO.

The company I thought was ideal to partner with apparently isn't interested. So I am bringing the design forward myself. Maybe later it will be easier to get a partner after I do more ground work.

Regarding cost, right now that fancy plug looks like the most expensive component, but I haven't investigated quantity pricing yet, hopefully I don't have to pay onsey-twosey price markups. I don't need hospital grade so there may be some cost savings available. 

The circuitry is not very expensive... I'm looking at using a higher voltage MOFSFET since I have already lost one in beta testing but that may be a fluke. Even with higher voltage mosfet the parts BOM is not too bad... but there is a bunch of parts, over 20 pops in the current version, so machine time may equal parts cost for the several resistors and diodes that are only pennies in production quantity.

Since you can't get a contract manufacturer to turn on their machines for less than a few hundred pieces, even this cheap BOM will add up. Most small parts will be bought on 5,000 piece reels. 

Using a stock off the shelf plug housing will save me some NRE for not having to tool up the plug housing (not trivial or cheap), I will still have the NRE for agency approval. I already spent $400 for the UL spec describing the current outlet tester... When I feel confident I can pass, I need to submit something like 9 units for them to test (which won't be cheap). In fact three of the nine units are for testing associated with the plug, so using an already UL listed component may allow me to forgo that mechanical plug specific testing. 

I have decided not to pursue a patent (already have that wall papered), which means if this is successful, I need to make hay before the competition copies it and under cuts me.

It is premature for me to even think about a firm price, I know that this is never going to compete with the $5 outlet testers (that don't work). My parts will cost me more than that.

I already have enough beer money to drink myself to death, so mainly want to get my capital investment back from this. I expect I am just now starting to spend real money. I actually enjoy the design part of this... This week I am learning about how MOSFETs fail, building stuff not so much fun, selling it even less. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Merlijn van Veen on November 19, 2015, 11:16:42 am
Great developments. Happy to read your pushing forward. Does this technology also apply to the EU?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 19, 2015, 11:40:13 am
Great developments. Happy to read your pushing forward. Does this technology also apply to the EU?

The general technology concept of using the human touch probe as the local 0V reference would work, but the diodes and MOSFET and resistor values would all need to be different, not to mention a different physical plug housing.

I am already looking at perhaps scaling up to a 400V mosfet (that could handle 230VAC) but I'm only using 300V diodes that can't handle 230VAC.

Yes a version could be made, but no I am not pursuing one at this time.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Merlijn van Veen on November 19, 2015, 11:50:55 am
Thanks for replying and good to know.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on November 19, 2015, 12:43:54 pm
I am already looking at perhaps scaling up to a 400V mosfet (that could handle 230VAC) but I'm only using 300V diodes that can't handle 230VAC.

I think that designing for 250V is a very good idea, as someone may have wired a NEMA 5-15R or 5-20R receptacle for 240V (in violation of code). I think it was Mr. Sokol that had personal experience with this...  :o

Which means that your tester might need to identify such a beast as incorrectly wired!
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 19, 2015, 12:54:52 pm
I think that designing for 250V is a very good idea, as someone may have wired a NEMA 5-15R or 5-20R receptacle for 240V (in violation of code). I think it was Mr. Sokol that had personal experience with this... ;-)

Which means that your tester might need to identify such a beast as incorrectly wired!
I need to beware feature creep... For now I want to KISS and get it working robustly for the basic function (identifying mis-wired outlets).

Too much/not enough voltage is easy enough to determine with a VOM.

At some point in the future I might mess around with trying to parse ground-neutral swaps, and ground quality (impedance), but this is an order of magnitude more complex (I'd use a microprocessor), and much lower demand.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on November 19, 2015, 02:30:06 pm
I need to beware feature creep... For now I want to KISS and get it working robustly for the basic function (identifying mis-wired outlets).

Too much/not enough voltage is easy enough to determine with a VOM.

At some point in the future I might mess around with trying to parse ground-neutral swaps, and ground quality (impedance), but this is an order of magnitude more complex (I'd use a microprocessor), and much lower demand.

JR

I guess I was figuring that it would somehow indicate voltage on both hot and neutral -- not necessary to parse the voltages. As for designing for 250V, what I meant was that the device would not be damaged by connecting to an outlet that's wired for 240V -- robustness. I agree with KISS.

I expect that people will plug in the "easy" thing first, and your Robert's Outlet Tester (RobOT) will be seen as easier to use than a VOM -- just like they reach for the commodity three-light outlet tester now.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 19, 2015, 02:42:13 pm
I guess I was figuring that it would somehow indicate voltage on both hot and neutral -- not necessary to parse the voltages. As for designing for 250V, what I meant was that the device would not be damaged by connecting to an outlet that's wired for 240V -- robustness. I agree with KISS.

I expect that people will plug in the "easy" thing first, and your Robert's Outlet Tester (RobOT) will be seen as easier to use than a VOM -- just like they reach for the commodity three-light outlet tester now.

I am going to be testing for insulation resistance with 500V, not crazy to push the technology up to 400V it's only money and size... (but people are already whining about price.  :o ).

JR

PS: Like the name (cute), while another promise to myself was never name a company after myself after seeing old obsolete Roberts tape recorders. My working name these days is OD-1 (outlet detective one), but I'll add RobOT to the short list. .
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 21, 2015, 12:13:25 pm
I think that designing for 250V is a very good idea, as someone may have wired a NEMA 5-15R or 5-20R receptacle for 240V (in violation of code). I think it was Mr. Sokol that had personal experience with this...  :o

Which means that your tester might need to identify such a beast as incorrectly wired!

For the forum members arguing for lower price, we may need to stop suggesting new features.  ;D

I have upgraded the diodes and MOSFET to 400V technology so accidental exposure to 240VAC will not harm it, some resistors could get hot but should be fine for brief exposure.

I have scratched out a simple indicator for 240VAC mains using a neon bulb, fed from a voltage divider. I haven't tested this on the bench yet but I should be able to pad down the mains voltage enough to ignore 120VAC and indicate when 240VAC is present.

If this extra feature is not needed or wanted I can just not populate the lamp. 

Getting close to cutting this third generation PCB loose. I will need to perform testing on this 3rd generation (like 500V insulation, etc), before i yank UL's chain to open a file and begin expensive testing. There are cheaper test labs, but if I want to actually change the UL spec to reflect my improved functionality that looks like only UL can do that.

Still making good progress. After spending hundreds of dollars on parts, it seems a false economy to not air ship the prototype PCBs from China.

JR

PS: Current working names,,, OD-1 (outlet detective), and RobOT (Roberts outlet tester), ....next?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on November 23, 2015, 02:16:41 pm
I got my 400V parts in today, but am just now finishing up on rev 3 layout of the PCB. (you will notice a subtle shape change, and no more LEDs on the back side. )

This time I am paying extra for DHL shipping from China so should be less than 3 weeks this time.  8) When spending hundreds of dollars for parts, it seems a false economy to not pay $19 for a couple weeks faster turn.

The window is officially closed for adding any more features  ;D  I did add pads to mount a neon lamp for 240V indication, but not sure whether this is really needed (or if it works, but it will probably work)..

JR

PS: While few will appreciate this, I managed to do this layout completely single sided, so could be even cheaper in production, but for small quantity you can't even buy single sided PCB... all the proto houses run 2 sided and just etch off the unwanted side.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 05, 2015, 08:35:26 pm
2 steps forward one step back...

Not great photography, but the new boards fit and work in the new package. Bad news is this one trips the grounded GFCI outlet too, so I need to revisit.

My math says it is less than 5 ma, but the GFCI is not happy so more bench work tomorrow. >:(

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 06, 2015, 10:52:31 am
SUCESS.... I had make a few more tweaks (as usual I stopped sharing circuit details). 

I now have it working with GFCI.

The picture shows a GFCI outlet wired RPBG, so the power (blue) and ground (top green LED) is lit... (It thinks a ground is present).

The red and yellow LEDs indicate that ground and neutral are hot....when I touch the probe.

SWEET.   8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 06, 2015, 11:00:18 am
Here is another picture with the bogus commercial outlet tester saying "all good" while the OD-1 is correctly warning about a hot ground.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on December 06, 2015, 12:17:42 pm
Here is another picture with the bogus commercial outlet tester saying "all good" while the OD-1 is correctly warning about a hot ground.

JR
Very cool.  Any backers/partners interested? 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 06, 2015, 01:13:09 pm
Very cool.  Any backers/partners interested?
I am not looking for financial backers, and the first company I tried to partner with did not say no, but pretty much went unresponsive. I didn't burn any bridges with them and may reengage after I get further along.

My ideal partner is somebody already in the business, so they have established distribution into the market, and experience with UL safety standards and UL certified manufacturing.

I have declined to apply for a patent, but am now investigating pursuing the UL approval by myself. I am unwilling to sell even onsey-twosey testers myself without UL blessing.

It isn't rocket science but mistakes can get expensive when learning how to do the agency approval dance by trial and error.  I bought the UL standard that covers the existing commercial tester ($400) and deciphered their creative use of the english language (I think).

I need to confirm the insulation resistance test (100M @ 500V), but since I got the tester working with 100M in series with the touch probe by definition it should pass, and by upgrading to 400V semiconductors the insulation testing shouldn't break it.

I can easily check the boxes for the listed tests that the commercial unit does, with some that it doesn't (like RPBG). 

One difficult spec is the mechanical integrity of the plug assembly but by using an already approved off the shelf part, I should be able to use that as a UL listed subassembly. I might even be able to skip that part of the approval testing (one of the three tests). In fact that off the shelf plug maker is next on my list to approach as a high value partner. 

I have more tweaking and testing to do, but it's looking pretty good.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on December 07, 2015, 12:02:34 am
I have declined to apply for a patent...

Have you explored the existing patents for similar devices, specifically for non-contact voltage testers? I'd hate for you to get into trouble for infringing on someone's patent. I realize that the design is entirely your own, but a patent holder with an independent but similar design could still claim infringement.

One of the lesser-realized purposes of a patent, rather than to prevent copycat works, is to prevent someone else from filing a patent on the same technology thereby preventing your own use of your design. Proving that your work is "prior art" in the face of a false patent claim is likely to be expensive and difficult when you don't already have a patent.

If you really don't want to file for a patent, then it may be in your best interest to open-source the final design. That will help to establish the design as "prior art". Alternatively, you sell the design to a manufacturer and let them patent it prior to release as a commercially-available product. The problem is that it can become an exclusive product, driving the cost higher than necessary and preventing widespread adoption of the product.

I recall that you already have many patents under your belt, so you are well aware of the issues. I'm just interested in making sure that your design isn't stolen and used -- or misused -- in ways that dishonor your intent.
Title: Re: brain storm an optimal human safety system for back line
Post by: Steve M Smith on December 07, 2015, 03:08:53 am
While few will appreciate this, I managed to do this layout completely single sided
That's always a nice achievement.
 
and deciphered their creative use of the english language
So it was written in American?!!


Steve.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 07, 2015, 10:28:41 am
Have you explored the existing patents for similar devices, specifically for non-contact voltage testers? I'd hate for you to get into trouble for infringing on someone's patent. I realize that the design is entirely your own, but a patent holder with an independent but similar design could still claim infringement.
Actually mine does not use non-contact technology. You need to contact mine to provide the local 0V reference.

I researched in the technology field of electronic touch controls and didn't find anything even close to my approach. 
Quote
One of the lesser-realized purposes of a patent, rather than to prevent copycat works, is to prevent someone else from filing a patent on the same technology thereby preventing your own use of your design. Proving that your work is "prior art" in the face of a false patent claim is likely to be expensive and difficult when you don't already have a patent.
The patent system rewards inventors with exclusive use for a limited time in exchange for publishing the knowledge so everybody else can learn from the invention and build upon it. I feel pretty confident I could prove my prior art inexpensively. I haven't exactly kept this secret, while a few months back I stopped publishing design improvement details, that I learned the hard way.  There are some subtle design details that are not obvious even to those skilled in electronics IMO. 
Quote
If you really don't want to file for a patent, then it may be in your best interest to open-source the final design. That will help to establish the design as "prior art". Alternatively, you sell the design to a manufacturer and let them patent it prior to release as a commercially-available product. The problem is that it can become an exclusive product, driving the cost higher than necessary and preventing widespread adoption of the product.
Again I haven't kept this secret so arguably it already is public domain. The US patent law used to require filing a patent application within one year of publication. International patent law stipulates filing before publication. I think the US may have harmonized with international law. I would assign my invention to a partner if they are willing to invest the money to pursue, but I suspect the horse may already left the barn. FWIW the beta test units I shipped out are equivalent to publication, not to mention my many discussions on the WWW. 
Quote
I recall that you already have many patents under your belt, so you are well aware of the issues. I'm just interested in making sure that your design isn't stolen and used -- or misused -- in ways that dishonor your intent.
My invention being copied would not break my heart... I am not doing this for the money. I need to keep some trade secrets about the design details in order to make this desirable for a partner to invest their resources into. At a minimum they need a head start on competition. In my exploration of partnership discussions I supplied a scrubbed scheamtic, that was missing a few critical circuit details.  8)

As i get older and more experienced, just because it is a good idea does not guarantee that it will happen or be commercially successful. I have faith in my design but not much more.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on December 08, 2015, 12:33:32 pm

As i get older and more experienced, just because it is a good idea does not guarantee that it will happen or be commercially successful. I have faith in my design but not much more.

JR

As a mechanical designer for hire I have learned that this is VERY true.
If you build a better mouse trap the world will ignore you.  You need a good idea AND marketing.

I completely understand you not doing anything with this without UL approval.  Years ago I came up with a much improved car seat for children.  It allowed mom to get the baby in and out of the car without straining her back.  When I thought of marketing it I thought Babies, Cars, No way.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on December 08, 2015, 02:04:04 pm
As a mechanical designer for hire I have learned that this is VERY true.
If you build a better mouse trap the world will ignore you.  You need a good idea AND marketing.

I completely understand you not doing anything with this without UL approval.  Years ago I came up with a much improved car seat for children.  It allowed mom to get the baby in and out of the car without straining her back.  When I thought of marketing it I thought Babies, Cars, No way.
While I was working at Peavey, they got sued because a musician playing two 3-wire grounded Peavey guitar amps got between a RPBG and properly grounded outlet, resulting in 120VAC between the two guitars. It was very nice to have UL sitting at our table in court to testify that our products were safe and absolutely didn't cause the musician's death. 

I don't expect any major problems from my OD-1 but in my experience lawyers are always cheaper if hired before the incident, as compared to after.

I could be temped to just say never-mind because of the UL hassle (I don't need the meager beer money this might provide), but I think an outlet tester that actually works is important and might even prevent some injuries if made available and used by the live sound community. 

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on December 08, 2015, 06:09:46 pm
While I was working at Peavey, they got sued because a musician playing two 3-wire grounded Peavey guitar amps got between a RPBG and properly grounded outlet, resulting in 120VAC between the two guitars. It was very nice to have UL sitting at our table in court to testify that our products were safe and absolutely didn't cause the musician's death. 

I don't expect any major problems from my OD-1 but in my experience lawyers are always cheaper if hired before the incident, as compared to after.

I could be temped to just say never-mind because of the UL hassle (I don't need the meager beer money this might provide), but I think an outlet tester that actually works is important and might even prevent some injuries if made available and used by the live sound community. 

JR
Complete agreement, and thank you
Frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 11, 2016, 01:00:40 pm
After a few week hiatus I am back on the bench with OD-1 development.

Attached is the latest PCB layout. I changed to a round PCB that better fits inside the commercial plug housing.

I wrestled with an interim change to make the ground present circuit simpler, and decided to return to the earlier, slightly more complicated version that ignores noisy grounds with leakage current. In my judgement it is better to not falsely report that a ground is present, than see that there is leakage current in a floating ground. The open ground is already a fault that should require attention. So no more feature creep.

I momentarily thought about adding another (yellow) LED to report leaky ground current, but decided that would be too much information/complexity for a simple tester.

I need to chew on this for a couple days before releasing to make sure my UL spacings are adequate, etc...

When I get this final cut PCB I will start testing for insulation resistance and the like. Since I'm not going to buy or rent a megger, I'll roll my own 500V power supply (danger Will Robinson). What could possibly go wrong?

JR

PS: I added pads where a neon lamp could indicate 240V, not sure if I will keep this feature, but will test it. Again perhaps TMI.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on January 11, 2016, 02:57:15 pm
While taking a walk today, I was thinking that I hadn't heard from JR's project.  Came back, and like magic, an updated post! 
Very happy to see things are moving after the holiday break.
FWIW, I agree with your decision on the ground circuit - not falsely reporting a ground present.
The additional yellow LED would have been a "nice to have", but that list could go on forever. 
Thanks for the update!
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 12, 2016, 02:15:53 pm
Just pulled the trigger on what hopefully is final cut.... Moved some stuff around to increase clearance from line and neutral... while UL only require 3/64" this is a small PCB so some tight fits.

Now in my spare time I can build my 500V PS for insulation testing.  :o :o

Not looking forward to arm wrestling with UL... Need to get them to change their spec where they require small print caveat in the instructions saying that these testers can't detect two hot leads... 8) 8) 8)  because mine does.

JR
[edit- boards shipped from china... 1-18  [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 25, 2016, 02:07:20 pm
got the PCB today but hole in the middle is not drilled out large enough.... oops.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on January 25, 2016, 03:55:42 pm
got the PCB today but hole in the middle is not drilled out large enough.... oops.

JR
Looks pretty snug around that hole to begin with...
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 25, 2016, 04:38:29 pm
Looks pretty snug around that hole to begin with...

Yup the whole design is snug, and some parts are close to the hole to be away from mains voltage leads. UL spacing is something around 3/64" but I tried to give them a little more room than that.

The extra ring around the hole is some kind of keep out area...I have a bunch of parts where their keep out areas interfere... 

I'll figure it out, but it won't be easy to drill 3/8" holes in a 1" diameter PCB.

They may have received a warning and decided to do me a favor, but making it only 1/8" is too much help.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on January 25, 2016, 08:53:05 pm
My guess is that an endmill in a drill press would work a lot better than a drill bit.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 25, 2016, 09:10:25 pm
My guess is that an endmill in a drill press would work a lot better than a drill bit.
I don't even have a drill press, but my roper whitney hand punch has die sets up to 9/32" so i can get pretty close with that.

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on January 25, 2016, 09:12:20 pm
My guess is that an endmill in a drill press would work a lot better than a drill bit.

Yes, and use a 1" collet to hold the PCB firmly and accurately located. The end mill does not need to be a centercutting design.

Edit:  never mind, if you don't have a drill press (or milling machine).
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on January 28, 2016, 03:11:58 pm
I am able to open up the undersized hole with roper whitney punch, and finish with dremel...

Right now I'm wrestling with trying to make it work with GFCI... outlet wired RPBG, but this probably depends on where the ground is bootlegged from, from output it should be all good as far as GFCI is concerned. 

another step forward.

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on January 28, 2016, 06:15:27 pm
Yep, the Dremel is the ticket.  PCB drills are very high speed carbide bits with very shallow points, almost like small end mills.  A PCB drill bit in a Dremel is a really handy tool to have for carving up any fiber reinforced plastics.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 04, 2016, 07:10:16 pm
Another step forward....

Since I changed to GFCI outlet in my RPBG test fixture, touching the test probe contact was tripping the GFCI from >5mA diverted to ground. (My bootleg ground to the input side of the GFCI) means the ground indication current is outside the GFCI loop.

I want my tester to still accurately report RPBG without tripping any GFCI.

My first attempt was a fail... I flipped the polarity of the ground present LED to be opposite and not in parallel with the ground fault LED. My approach worked to get the current down, but caused a new problem, if the ground was floating the two ground LEDs conducted through each other so got two false indications.   :(

Suck-cess....  I reduced the current in both the red ground hot fault LED, and the normal ground LED still in parallel to keep the total current less than the trip threshold.

I still need to test my 240V (added neon lamp) feature.  But this is getting really damn close to done. Nothing left to fix...:-)

After that maybe 240V feature is tested I get to fire up my 500v ps to test for leakage.  :o :o :o

JR   
Title: Re: brain storm an optimal human safety system for back line
Post by: Josh Rawls on February 04, 2016, 08:43:42 pm
Another step forward....

Since I changed to GFCI outlet in my RPBG test fixture, touching the test probe contact was tripping the GFCI from >5mA diverted to ground. (My bootleg ground to the input side of the GFCI) means the ground indication current is outside the GFCI loop.

I want my tester to still accurately report RPBG without tripping any GFCI.

My first attempt was a fail... I flipped the polarity of the ground present LED to be opposite and not in parallel with the ground fault LED. My approach worked to get the current down, but caused a new problem, if the ground was floating the two ground LEDs conducted through each other so got two false indications.   :(

Suck-cess....  I reduced the current in both the red ground hot fault LED, and the normal ground LED still in parallel to keep the total current less than the trip threshold.

I still need to test my 240V (added neon lamp) feature.  But this is getting really damn close to done. Nothing left to fix...:-)

After that maybe 240V feature is tested I get to fire up my 500v ps to test for leakage.  :o :o :o

JR   

I'm excited to see your progress. When these are on the market I will order a few of them. For now I have trained all my DJs how to test an outlet with a meter and a NCVD.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2016, 11:21:58 am
I want my tester to still accurately report RPBG without tripping any GFCI.

Report from the field. Call me to discuss details, but the prototype does seem to 100% indicate on an RPBG, and will find an elevated ground as low as 75 volts with me being completely isolated from earth. If I'm physically high-z grounded by laying my hand on a painted metal surface, it will indicate an elevated ground as low as 30 volts. Don't worry, I'm being careful with this.

No GFCI's were tripped during these experiments...  ;)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 05, 2016, 12:54:53 pm
Report from the field. Call me to discuss details, but the prototype does seem to 100% indicate on an RPBG, and will find an elevated ground as low as 75 volts with me being completely isolated from earth. If I'm physically high-z grounded by laying my hand on a painted metal surface, it will indicate an elevated ground as low as 30 volts. Don't worry, I'm being careful with this.

No GFCI's were tripped during these experiments...  ;)
The input resistance is 100 MegOhm so no hazard.

One question I have pondered is what happens if you are standing inside a hot-skin RV? It seems like then the local ground reference voltage would be 120VAC.  :o :o  Of course I don't expect you to ever get inside a hot skin RV to find out (I sure wouldn't).

Plugging the OD-1 into one of the RV's external outlets would reveal the hazard without exposing the human (unless the outlet has a grounded metal outlet cover you have to open that is energized). NCVT is the play before approaching any RV.

 thanx for the feedback...

JR

PS: Mike's OD-1 prototype is not using the latest low current ground LED resistors so would trip my GFCI/RPBG test fixture. If the ground bootleg is performed on the output side of the GFCI the ground current stays inside the detection loop so won't trip. RPBG are bad... :o 



Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 05, 2016, 01:57:27 pm
One question I have pondered is what happens if you are standing inside a hot-skin RV? It seems like then the local ground reference voltage would be 120VAC.  :o :o  Of course I don't expect you to ever get inside a hot skin RV to find out (I sure wouldn't).

Well, if it's a Airstream (stainless steel skin) parked next to another Airstream trailer, also with a hot skin but connected to the other pole of the 240V circuit, then they'd both be electromagnets of opposite polarity. Since opposites attract, they'd sidle up to each other through magnetism, short out, and melt down. You're right, I wouldn't want to be standing in one, either. ;-)

Of course, that wouldn't happen. But we can imagine, can't we?

It's not wise to step into an RV with a hot skin condition, as becoming part of a circuit between hot and ground generally does not bode well for that person. However, if you step inside to do measurements and then the hot chassis condition is applied, you *should* be safe as you will be at the same potential as the local ground reference inside the trailer.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2016, 02:29:46 pm
It's not wise to step into an RV with a hot skin condition, as becoming part of a circuit between hot and ground generally does not bode well for that person. However, if you step inside to do measurements and then the hot chassis condition is applied, you *should* be safe as you will be at the same potential as the local ground reference inside the trailer.
Uhmmmm.... Here I am doing exactly that in a video. You can see me standing on the steps of an RV electrified with a hot-skin potential of 120-volts AC using a NCVT to test for a hot ground. Starts around 4:45 or so in the video.

https://www.youtube.com/watch?v=Y8h64X33aKg&list=PLbNmdE7sBb0dt0zyv6ULMeacIcqvxwuNO

Yeah, I have too much fun with this...
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on February 05, 2016, 02:56:17 pm
Well, if it's a Airstream (stainless steel skin) parked next to another Airstream trailer, also with a hot skin but connected to the other pole of the 240V circuit, then they'd both be electromagnets of opposite polarity. Since opposites attract, they'd sidle up to each other through magnetism, short out, and melt down. You're right, I wouldn't want to be standing in one, either. ;-)


I think they would slide up to one another and the next thing you know there is a little teardrop trailer.
(https://s-media-cache-ak0.pinimg.com/564x/61/3a/59/613a59bf33c947600b2f19c90d15f8fc.jpg)
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on February 05, 2016, 03:38:15 pm
I think they would slide up to one another and the next thing you know there is a little teardrop trailer.

Sort of like a bigger version of how synthesizers are made.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 05, 2016, 06:57:13 pm
Uhmmmm.... Here I am doing exactly that in a video. You can see me standing on the steps of an RV electrified with a hot-skin potential of 120-volts AC using a NCVT to test for a hot ground. Starts around 4:45 or so in the video.

https://www.youtube.com/watch?v=Y8h64X33aKg&list=PLbNmdE7sBb0dt0zyv6ULMeacIcqvxwuNO

Yeah, I have too much fun with this...
Thanx... that's pretty much what I expected...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 07, 2016, 01:58:23 pm
Well I just tried the the neon 240V detector and A) the resistor ratio I used doesn't drop the normal 120V enough (only 50%) so it's lighting up even with 120V, and B) it doesn't fit inside that plug... (unless I completely redesign the PCB with a cut out to make room). 

I may just drop this feature for now (well see).   :'(

Next step is to rig up a 500VAC supply to test insulation resistance. Don't try this at home.  :o :o

JR

PS: Yesterday I repaired the OD-1 I blew up with my first attempt to reduce the ground current. Fried two LEDs and the mosfet... working again now....  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: Rob Spence on February 07, 2016, 05:59:46 pm
John, I have a Fluke 1503 insulation tester you could borrow if it would help you.


Sent from my iPad using Tapatalk HD
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on February 07, 2016, 07:17:07 pm
Well I just tried the the neon 240V detector and A) the resistor ratio I used doesn't drop the normal 120V enough (only 50%) so it's lighting up even with 120V, and B) it doesn't fit inside that plug... (unless I completely redesign the PCB with a cut out to make room). 

I may just drop this feature for now (well see).   :'(

Next step is to rig up a 500VAC supply to test insulation resistance. Don't try this at home.  :o :o

JR

PS: Yesterday I repaired the OD-1 I blew up with my first attempt to reduce the ground current. Fried two LEDs and the mosfet... working again now....  8)

Obligatory topic swerve:  what do you have fermenting whilst you're playing with electricity?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 07, 2016, 07:19:06 pm
John, I have a Fluke 1503 insulation tester you could borrow if it would help you.


Sent from my iPad using Tapatalk HD
I may take you up on that. I'm too cheap to buy one.

UL requires 100M insulation at 500V... I just looked up the Fluke and looks like the perfect tool for the job.

I'll contact you off list, thanx.

=======

I just finished my jury rigged DIY insulation test and my test results were not definitively concise.

From the attached picture I used 4x mains transformers I had laying around, the voltage doesn't much matter.  I connect mains voltage to the primary of one, then wire all the secondaries in parallel, so the first one drives the other three. Last, I stack the primaries on top of the first one, making a kind of auto-former that should deliver 4x mains voltage.

I measure 444V at the output so close enough for government work.

Part 2 I added a 10M resistor in series with this voltage output so I can measure the drop across it to impute my insulation resistance as a voltage divider with the 10M. But for the bad news my Rat Shack meter exhibits a roughly 10M input impedance, not bad for a 15 year old $25 meter, but my no load test voltage measurement is already scrubbing off about half my test voltage (220V).

Part 3, In theory, I can measure the drop with the OD-1 being probed (one lead at a time) and then calculate a resistance in parallel with the meter's 10M.

OK, I got results and they come in right around 100M but now I'm already testing the OD-1 at less than 1/2 the proscribed test voltage, and trying to parse out a resistance that is 20x my source resistance (5M) so not very accurate.

The good news is no smoke was released, and I didn't kill myself... but I can't stick a fork in this spec yet... Since I have a 100M resistor in series with my probe input it is hard to image resistance ever being less than that.. but this is all about empirical measurement, not my speculation.   

I need to soak this in beer over night for other angles of attack...

I expect my scope's 10x probe is higher input impedance (100M?)  than my rat shack meter but I will need to be careful about how I ground it since my 500V supply is not isolated from the mains. I guess I could add another transformer to my rig and completely float the 500V.

DON'T TRY THIS AT HOME... danger Will Robinson.

I'll count this as a half step forward, it clearly didn't fail... just didn't pass with a fat margin of certainty.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 07, 2016, 07:21:41 pm
Obligatory topic swerve:  what do you have fermenting whilst you're playing with electricity?
Johnny Stout,,, but I don't partake of the hopped refreshment while messing with 450VAC on the bench...

Finished with the High Voltage bench for now, so Johnny beer it is.

JR

[edit] I revisited using VOM in current range and measured between 7 and 11 uA... on paper calculates to 40-60 Meg so < 100M.  :-\   Not sure I can trust that measurement.  [/edit]

Title: Re: brain storm an optimal human safety system for back line
Post by: Rob Spence on February 08, 2016, 11:14:45 pm
I may take you up on that. I'm too cheap to buy one.

UL requires 100M insulation at 500V... I just looked up the Fluke and looks like the perfect tool for the job.

I'll contact you off list, thanx.

=======

I just finished my jury rigged DIY insulation test and my test results were not definitively concise.

From the attached picture I used 4x mains transformers I had laying around, the voltage doesn't much matter.  I connect mains voltage to the primary of one, then wire all the secondaries in parallel, so the first one drives the other three. Last, I stack the primaries on top of the first one, making a kind of auto-former that should deliver 4x mains voltage.

I measure 444V at the output so close enough for government work.

Part 2 I added a 10M resistor in series with this voltage output so I can measure the drop across it to impute my insulation resistance as a voltage divider with the 10M. But for the bad news my Rat Shack meter exhibits a roughly 10M input impedance, not bad for a 15 year old $25 meter, but my no load test voltage measurement is already scrubbing off about half my test voltage (220V).

Part 3, In theory, I can measure the drop with the OD-1 being probed (one lead at a time) and then calculate a resistance in parallel with the meter's 10M.

OK, I got results and they come in right around 100M but now I'm already testing the OD-1 at less than 1/2 the proscribed test voltage, and trying to parse out a resistance that is 20x my source resistance (5M) so not very accurate.

The good news is no smoke was released, and I didn't kill myself... but I can't stick a fork in this spec yet... Since I have a 100M resistor in series with my probe input it is hard to image resistance ever being less than that.. but this is all about empirical measurement, not my speculation.   

I need to soak this in beer over night for other angles of attack...

I expect my scope's 10x probe is higher input impedance (100M?)  than my rat shack meter but I will need to be careful about how I ground it since my 500V supply is not isolated from the mains. I guess I could add another transformer to my rig and completely float the 500V.

DON'T TRY THIS AT HOME... danger Will Robinson.

I'll count this as a half step forward, it clearly didn't fail... just didn't pass with a fat margin of certainty.

JR

Tester is on the way. While it can be dangerous too , not so much as the diy rig 😀


Sent from my iPad using Tapatalk HD
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 11, 2016, 02:26:05 pm
Thanks to Rob I now have a reliable and safer way to measure insulation resistance... The interesting thing is his proper (FLUKE) tester confirmed my crude estimate of 60M, so kinda good/bad news.  ???

Digging a little deeper there are voltage issues with small SMD resistors (my parts are only rated for something like 50V.

I can find a single SMD resistor that handles 600V but it cost $0.70 in thousands several dollars in small quantity, so i think I will cover that base with two $0.07 resistors in series. Looks like one more cut of PCB to fit in the extra parts.

Just for chuckles I stacked up two of my small 100M resistors in series, and confirm that my probe delivers  160M of insulation resistance at 500V so that is a PASS... and it still works with 160M (probably 200M at low voltage) in series with input... for production I'll probably target closer to 100M but comfortably above.

Another step closer... This would have been much more expensive for me if UL tested and found this. So all good and thanks again to Rob for the loan... nothing like using the right tool for the job.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 18, 2016, 12:30:13 pm
I just ordered what should be my final prototype PCB (from China).

I have fixed all known issues, and bailed on the 240V indication (not enough room).

I fixed one problem, that in hindsight I am not sure I should fix.

When testing a RPBG wired GFCI outlet (with ground bootstrap to the input side of the GFCI) the combined current of red ground hot fault LED + the normal ground present green LED, would equal more than 5mA and trip the GFCI. I can reduce the current of both so it can indicate RPBG without tripping the GFCI, but I am not sure that is necessary or even desirable. If the outlet tester trips the GFCI that should be a good indication that something is wrong.

My earlier version would trip GFCI just from the ground LED but that is now fixed (UL spec's that ground current to be less than 2mA so well below the 5mA trip current by itself). What I am debating now is should the OD-1 indicate properly with RPBG wired GFCI or just trip the GFCI?  My preference now is leaning toward trip it. The red and yellow LEDs flash momentarily before it trips...

This is just a matter of using different resistor values so i can make this decision later, but I would like to ask this well informed interest group for preferences??   

Trip or not trip a RPBG wired GFCI... ? (these should be pretty rare).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on February 18, 2016, 02:22:49 pm
I would let it trip it and not worry too much about it.  I am thinking that a RPBG GFCI would trip nearly anytime anything was plugged into it, so I doubt they would remain in the wild for any length of time.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 18, 2016, 03:34:25 pm
I would let it trip it and not worry too much about it.  I am thinking that a RPBG GFCI would trip nearly anytime anything was plugged into it, so I doubt they would remain in the wild for any length of time.

If they bootleg the ground to the output side of the GFCI at least that path will be inside the loop and not trip the GFCI, while any current leaking to the outside world will trip.

I will register your vote for trip...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 18, 2016, 04:50:32 pm
How does your tester respond to a proper-polarity bootleg ground (ground screw jumpered to neutral screw; neutral screw actually wired to neutral)? Is it happy as a clam?

I can't remember if this was discussed, and I don't want to wade through 400+ posts.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 18, 2016, 06:08:39 pm
How does your tester respond to a proper-polarity bootleg ground (ground screw jumpered to neutral screw; neutral screw actually wired to neutral)? Is it happy as a clam?

I can't remember if this was discussed, and I don't want to wade through 400+ posts.
Yes it registers exactly the same as a true ground.

It even reports the RPBG ground as a valid connection, but it also registers that neutral and ground are energized. If the red LED says the ground is hot, ignore the green LED saying that a ground path is present.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on February 18, 2016, 08:00:55 pm
Yes it registers exactly the same as a true ground.

It even reports the RPBG ground as a valid connection, but it also registers that neutral and ground are energized. If the red LED says the ground is hot, ignore the green LED saying that a ground path is present.  8)

JR

Aha! So it CAN be fooled! Charlatan!!!  :o ??? ::) 8)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on February 18, 2016, 08:19:30 pm
Aha! So it CAN be fooled! Charlatan!!!  :o ??? ::) 8)
If you ignore the bright red LED warning you.....  :o

A ground being connected is not as important as it being 120V!

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 17, 2016, 01:11:53 pm
Since the last cut OD-1 PCB is already obsolete due to further refinements ( a problem with slow shipping and fast tweaks). I decided to wail until it arrives, to confirm that my chinese PCB fab got the holes right this time (last ones were too small.) Since these boards are coming slow boat they still haven't arrived (already 3+ weeks since they left hong kong). I expect them any day.

As I refine the design for cost and UL acceptance, I feel like I am very close. In a strange pricing quirk, I can buy a 1W 100M resistor rated for 600V for $0.14, while the more sensible 1/4W resistor is $0.75 in quantity.  ::)

Note: the huge 1W resistor just above the center hole in the PCB layout, I placed a 1/4W resistor on top of it, so I can use either in the final build, should I find a more sensibly priced 1/4W resistor later.

I struck out with the second company that I was trying to partner with (maybe it's me?  >:( ) 

I have prepared a web page to better tell the OD-1 story  http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1)  Please feel free to share my webpage with anyone you think might be interested. I need to cast a wider net, or I will literally have to manufacture these myself.

JR

 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 19, 2016, 12:28:09 pm
The good news is that the previous (already obsolete) cut of PCB arrived this morning and the holes are the right size...so no more excuses... I will probably spend the weekend checking for spacing and layout tweaks.. before releasing the LAST FINAL PCB DESIGN.

UL has rules for spacing between line or neutral conductors and conductive metal, but I will even try to maintain that UL spacing to any exposed solder contacts. The only exposed piece of metal in my tester has an 100M resistor in series. 

I don't think I'll wait for slow boat delivery this time, that was like 3 1/2 weeks.. It will double the cost of the PCBs but time is money and I'm getting impatient (old).

Regarding final feature set:

*It will NOT trip GFCI outlets. The UL spec stipulates <2mA ground current, so less than the 5mA trip leakage.

*The ground present LED only indicates that a ground path is present (or not), not the quality of that ground.

*It will detect line-neutral reversed and hot safety ground situations (like RPBG).

JR

PS: please share this link with anyone you know who does electrical work http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1) You don't want to make me build these...

 
 
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on March 20, 2016, 12:11:40 pm
PS: please share this link with anyone you know who does electrical work http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1) You don't want to make me build these...


I think you had mentioned that offering them as a kit is just not feasible - due to your past experience with offering kits, UL rating, and the inability of most mortals to not be able to solder/work with SMD components.   Do I have that basically correct?


Here's hoping you find someone!


frank
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 20, 2016, 12:21:54 pm

I think you had mentioned that offering them as a kit is just not feasible - due to your past experience with offering kits, UL rating, and the inability of most mortals to not be able to solder/work with SMD components.   Do I have that basically correct?
Since I have been hand assembling these prototypes myself,,, I can assure you these would not make a good kit product. Not only would I be uncomfortable about exposing consumers to hazards from incorrect assembly, UL not only certifies the design, but that the factory building them will follow that design and only use the specified components.

UL was a regular visitor to the Peavey factories to check our work. 
Quote

Here's hoping you find someone!


frank
Thanks... me too...

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on March 20, 2016, 02:17:27 pm
There's a lot of manufacturing capacity in Meridian these days...
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 20, 2016, 02:34:46 pm
There's a lot of manufacturing capacity in Meridian these days...
Where? 

The Peavey plant that used to assemble SMD was about 7 miles up the same road my house is on.  Perhaps why I bought this house, back then. 7 mile commute to work, without even one stop sign.

Those machines have been sold and that factory shuttered, years ago.

Working with Peavey would be like remarrying an ex-wife... never a good idea.

JR

PS: I kept a copy of that Undercover Boss episode on my DVR if I ever need a reminder.  ::)
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on March 20, 2016, 04:14:34 pm
Where? 

The Peavey plant that used to assemble SMD was about 7 miles up the same road my house is on.  Perhaps why I bought this house, back then. 7 mile commute to work, without even one stop sign.

Those machines have been sold and that factory shuttered, years ago.

Working with Peavey would be like remarrying an ex-wife... never a good idea.

JR

PS: I kept a copy of that Undercover Boss episode on my DVR if I ever need a reminder.  ::)

Don't re-marry, just date.  At arms length.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 20, 2016, 06:53:24 pm
Don't re-marry, just date.  At arms length.
It looks like it is going to take more than a casual date to get somebody to make these... It seems like a no-brainer to me, but what would I know.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on March 20, 2016, 09:12:28 pm
It looks like it is going to take more than a casual date to get somebody to make these... It seems like a no-brainer to me, but what would I know.

JR

The manufacturing is the easy part. There are any number of contract manufacturers out there both in the USA and overseas (such as Sparton Corporation (http://sparton.com/), a company that acquired another company that my wife worked for a decade ago).

The hard part is marketing: finding someone to take the product, turn it into a brand, and get it into the hands of electricians, musicians, consumers, inspectors and anyone else playing with electricity. Ideally, it would be an existing marketer of electrical tools and test gear, such as Fluke, Sperry, Ideal, GB, Greenlee, or any number of other manufacturers that you find in the big box and hardware stores.

Both Home Depot and Lowe's have their own house brands of wiring tools (Commercial Electric and Southwire, respectively -- I think Southwire is licensed by Lowe's just like Ridgid is licensed by HD). Maybe you could talk one of them into adopting the product -- they might like the idea of an "exclusive" product that's better than anything else out there, and cheap enough to make that they could turn a good profit.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 21, 2016, 11:38:28 am
The manufacturing is the easy part. There are any number of contract manufacturers out there both in the USA and overseas (such as Sparton Corporation (http://sparton.com/), a company that acquired another company that my wife worked for a decade ago).
of course, I was speaking broadly since this is an audio (electrical safety) forum.
Quote
The hard part is marketing: finding someone to take the product, turn it into a brand, and get it into the hands of electricians, musicians, consumers, inspectors and anyone else playing with electricity. Ideally, it would be an existing marketer of electrical tools and test gear, such as Fluke, Sperry, Ideal, GB, Greenlee, or any number of other manufacturers that you find in the big box and hardware stores.
The major hurdle is finding someone already in the business, who is also willing and capable of spending significant dollars to tool up a custom product, and then get UL to approve that product, and finally sell enough with a high enough profit margin to recapture that initial investment and make a profit. 
Quote
Both Home Depot and Lowe's have their own house brands of wiring tools (Commercial Electric and Southwire, respectively -- I think Southwire is licensed by Lowe's just like Ridgid is licensed by HD). Maybe you could talk one of them into adopting the product -- they might like the idea of an "exclusive" product that's better than anything else out there, and cheap enough to make that they could turn a good profit.
I have a short list but have already wasted a lot of time with prolonged exclusive serial discussions with two possible partners. I am now looking to expand my reach and cast a wider net with the web page I published.

FWIW I spent a couple years of my time at Peavey, being the guy who reviewed external idea submissions. I rejected everything I saw during my tenure doing that. NIH is a huge hurdle to overcome.

I guess another idea is to get a Chinese manufacturer who is hungry and willing to tool up and approve this product. Then they could private label it, like the current 3 lamp tester is. But I have no desire to wrestle with snakes.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on March 21, 2016, 11:44:03 am
JR, call me about this... I have an idea.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 21, 2016, 12:25:26 pm
JR, call me about this... I have an idea.
I need to do my day job right now (instead of wanking on the WWW), but I'll try to call later today, or email.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on March 21, 2016, 12:32:16 pm

PS: I kept a copy of that Undercover Boss episode on my DVR if I ever need a reminder.  ::)
I gotta admit, I was rather shocked when I saw it.
Kind of blew my image of Hartley.
JR, How much of an influence on Hartley, and Peavey was Melina ?

Chris.
Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on March 21, 2016, 12:37:04 pm
I gotta admit, I was rather shocked when I saw it.
Kind of blew my image of Hartley.
JR, How much of an influence on Hartley, and Peavey was Melina ?

Chris.

Melia Peavey was a very charitable lady who died too young (43, IIRC) in 2003.  JR will have to fill in the rest.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 21, 2016, 01:23:21 pm
I gotta admit, I was rather shocked when I saw it.
Kind of blew my image of Hartley.
JR, How much of an influence on Hartley, and Peavey was Melina ?

Chris.
I actually reported to Melia for several years, so I have strong opinions (that even though she is dead, RIP I will keep private).

Melia came up from within so she knew the company well, she was also very smart and as President ran the entire operation. Hartley was the good cop and idea guy, she was the bad cop and tough as nails operations person.

Since I worked there for 15 years, and quit over disagreements with the man whose name is on the buildings, I did not find anything about the Undercover Boss surprising other than the fact that they actually agreed to do it. That show is a bad joke, a modern day version of "queen for a day". The big give-aways are scripted part of the deal agreed to in advance, the buy in for the ASSumed good publicity result. Such selective rewards are pretty much guaranteed to tick off all the other workers who don't get rewarded. Asking long time Peavey workers who have seen their benefits cut, and so many fellow co-workers laid off, how they feel about the company and their future is never going to turn out well, and it didn't.  :-[ 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on March 21, 2016, 03:31:51 pm
I actually reported to Melia for several years, so I have strong opinions (that even though she is dead, RIP I will keep private).

Melia came up from within so she knew the company well, she was also very smart and as President ran the entire operation. Hartley was the good cop and idea guy, she was the bad cop and tough as nails operations person.

Since I worked there for 15 years, and quit over disagreements with the man whose name is on the buildings, I did not find anything about the Undercover Boss surprising other than the fact that they actually agreed to do it. That show is a bad joke, a modern day version of "queen for a day". The big give-aways are scripted part of the deal agreed to in advance, the buy in for the ASSumed good publicity result. Such selective rewards are pretty much guaranteed to tick off all the other workers who don't get rewarded. Asking long time Peavey workers who have seen their benefits cut, and so many fellow co-workers laid off, how they feel about the company and their future is never going to turn out well, and it didn't.  :-[ 

JR
JR, I respect your view on Melia completely.
I was not a fan of that show, but a few companies caught my attention. ADT and Peavey in particular. I still have some Peavey gear, and my first job out of high school was electronics tech and armed response for ADT.
For Peavey, that show was NOT good publicity. It portrayed Hartley as more of a buffoon than a pioneer and leader in industry, which I feel he was, before the "race to the bottom" started. If Melia were still around, do you think things would have turned out better, or was that race lost at the start ? (no, i am not asking you to polish off the old crystal ball)

Chris. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 21, 2016, 05:59:57 pm
JR, I respect your view on Melia completely.
I was not a fan of that show, but a few companies caught my attention. ADT and Peavey in particular. I still have some Peavey gear, and my first job out of high school was electronics tech and armed response for ADT.
For Peavey, that show was NOT good publicity.
They were either completely ignorant of that show, or delusional about how the remaining Peavey workers view the company. I suspect a little of both...  Even Cortland's girlfriend didn't want him to do it, probably for different reasons, but that's why he pretended to live out at the Peavey Museum guest house for that filming (she threw him out of their apartment). Sorry probably TMI 
Quote
It portrayed Hartley as more of a buffoon than a pioneer and leader in industry, which I feel he was, before the "race to the bottom" started.
Hartley was always about delivering music products that didn't suck for a fair price. Over the years I've seen him walk back several things he said he would "never ever" do. Hartley has probably disengaged from the day to day running of the business. I know several design engineers still working there and Hartley surely still participates in hands-on product feature set design decisions.
Quote
If Melia were still around, do you think things would have turned out better, or was that race lost at the start ? (no, i am not asking you to polish off the old crystal ball)

Chris.
Define better? Hartley is probably doing about as good as he could do with not being the cheapest, or best, anything. The middle can be an ugly place, kind of like a "cute" blind date.

I was working at Peavey when we were in the planning stage to build our own factory in mainland China (that money instead was used to purchase Crest). I had meetings with a chinese OEM about building a value Chinese power amp that didn't suck, well before QSC did theirs. My amp project got dragged back to be built in the US, at a much higher price, with so-so results. We had an IMO serious president for a while (brought in from the outside after Melia died.). Me and several others inside had visions of taking Peavey up to the next level. I wanted to leverage the clear technology advantage held by Media-matrix as an icon to reposition Peavey upscale, not unlike how Sony repositioned themselves away from their cheap transistor radio past, to a high tech "Trinitron" TV future. Needless to say my vision didn't get fulfilled. :'( In fact many things I/we did back then have been unwound. The modern logo I had on many of my products has been dumped for the old lightning bolt logo that Hartley drew on his HS notebook cover.

I am too close to it to be completely objective, but no I don't think losing Melia was a significant problem (other than for her RIP). As I've been told recently manufacturing stuff isn't the hard part.  8)     

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on March 22, 2016, 12:47:11 pm
I am too close to it to be completely objective, but no I don't think losing Melia was a significant problem (other than for her RIP). As I've been told recently manufacturing stuff isn't the hard part.  8)     

JR
Thanks for sharing JR. Insightful, as always.
Chris.
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on March 22, 2016, 08:16:21 pm
Appreciate the candor John
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 23, 2016, 12:05:33 am
Appreciate the candor John
I didn't tell you the good stuff... I've got stories... ;D ;D

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on March 23, 2016, 01:22:29 am
I didn't tell you the good stuff... I've got stories... ;D ;D

JR

As much as we might enjoy hearing of others' foibles, telling those stories is unlikely to serve any good purpose.

Know that they, as we, all have faults, but let us hold each other in highest regard and mutual respect.
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on March 23, 2016, 03:05:20 am
As much as we might enjoy hearing of others' foibles, telling those stories is unlikely to serve any good purpose.

Know that they, as we, all have faults, but let us hold each other in highest regard and mutual respect.

Gossip is evil.  It's a fine line.  To a certain extent this is historical.  Nobody can dispute Peavey's role in defining the prosumer market.

Title: Re: brain storm an optimal human safety system for back line
Post by: Tim McCulloch on March 23, 2016, 11:55:43 am
Gossip is evil.  It's a fine line.  To a certain extent this is historical.  Nobody can dispute Peavey's role in defining the prosumer market.

It's not gossip if it's demonstrable truth.  That said there is often little productivity in recalling the past with a jaundiced eye - history cannot be changed and any future between most of the parties is unlikely.

I know that my view of Hartley, Inc is based only on my outside observations and the limited contact I had with persons employed there (whose information may have been no better than my own).  John's comment about the executive trade-off of China plant or Crest is one example of battling crystal balls - in the Analog Crystal Ball the purchase of Crest looked good; in the Digital Crystal Ball owning a plant in China looked better.  Ultimately the ACB was playing a re-run while the DCB was receiving a new program, and the Guy Who Decides liked the re-run better.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on March 23, 2016, 12:28:38 pm
As much as we might enjoy hearing of others' foibles, telling those stories is unlikely to serve any good purpose.

Know that they, as we, all have faults, but let us hold each other in highest regard and mutual respect.

We must consider why we share stories of others: is it to build up or tear down? A negative story CAN be turned positive, if the subjects of the story or the conversants use it as a learning experience. It will never be a positive when shared as dirty gossip.

As for the Undercover Boss episode, Peavey brought that upon themselves knowing that however it turned out --good or bad -- it would be in the public eye. That story has been well-hashed here (http://forums.prosoundweb.com/index.php/topic,153441.0.html) previously; I see little benefit to re-enter that discussion.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 23, 2016, 12:35:26 pm
It's not gossip if it's demonstrable truth.  That said there is often little productivity in recalling the past with a jaundiced eye - history cannot be changed and any future between most of the parties is unlikely.

I know that my view of Hartley, Inc is based only on my outside observations and the limited contact I had with persons employed there (whose information may have been no better than my own).  John's comment about the executive trade-off of China plant or Crest is one example of battling crystal balls - in the Analog Crystal Ball the purchase of Crest looked good; in the Digital Crystal Ball owning a plant in China looked better.  Ultimately the ACB was playing a re-run while the DCB was receiving a new program, and the Guy Who Decides liked the re-run better.
I try not to share too much inside information but a decade or two later it seems relatively harmless, and perhaps informative to the questions asked. IMO it was an important fork in the road with two distinct paths leading to different potential outcomes. While nobody asked me, i preferred hanging out in NJ where Crest was based and I grew up, to spending time in China. 

JR

PS: I only mentioned UB as shorthand to explain my reluctance to approach Peavey regarding my outlet tester. I expect that suggestion was made at least partly in jest if not wholly.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on March 23, 2016, 12:42:07 pm
Guys, even though everyone is playing nicely on this OT swerve, we don't want this thread to turn into personality bashing. Let's move on to technology concerns...
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on March 25, 2016, 12:41:46 pm
Guys, even though everyone is playing nicely on this OT swerve, we don't want this thread to turn into personality bashing. Let's move on to technology concerns...
Yes drill sargeant  ;D ;D

It's been a crazy week.. I sold/shipped more drum tuners this week than some recent months but I'd be crazy to complain about that. I'm finally getting caught back up.

I just pulled the trigger on my LAST EVER OD-1 pcb order. This time I paid up for DHL shipping from china so I don't have to wait 3+ weeks.

I need to order a few more SMD parts but they are not a rush...

Back in my early generation PCBs I was able to lay these out single sided with room to spare... now this is one tight puppy using traces on both sides. One big difference is using higher voltage resistors, higher voltage diodes etc. that are physically larger.

more later... another step forward.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 19, 2016, 08:45:21 pm
Finished my taxes... back to the bench.

built up 3 tested one.... Happily spanked the 100M insulation test at 500V (Thanks again Rob)  ;D UL kiss my grits.

You can see the cheaper 1W resistor on one board and the more expensive  1/4W on the other.

I didn't order 2 resistor values that I need (dumbass), but they don't impact the testing.

Another big step forward.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 23, 2016, 02:59:49 pm
I just ordered 4 new resistor values, so I can get this version rocking ($4. for 400 resistors, the postage will cost more than the parts). 

2 values I forgot to order, one tweak that makes it work better, and another maybe tweak. I have all three boards I built up working, but one resistor with 160V across it is only rated for 75V (150V overload). Next week I'll get it squared away with a 200V part. 

Since the insulation resistance test uses DC I decided to measure it with the voltage polarity reversed... that way it measures even better 160M.

I've got another company I approached about partnering on this ignoring me... (Maybe it's me).  :-\

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on April 23, 2016, 11:12:50 pm
More likely a lack of understanding.  I'm fairly certain a surprisingly high percentage of "licensed electricians" would need more than a few minutes of instruction to understand the benefits-I could name a few in my business area-but won't.  I don't envy anyone trying to explain the benefits to an exec.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 24, 2016, 11:53:39 am
More likely a lack of understanding.  I'm fairly certain a surprisingly high percentage of "licensed electricians" would need more than a few minutes of instruction to understand the benefits-I could name a few in my business area-but won't.  I don't envy anyone trying to explain the benefits to an exec.
I'm not sure it is just that, but agreed we need to raise awareness that RPBG can and has killed people, and the widely used 3 lamp tester ignores RPBG, indicating good. I got so tired of explaining it that I published a web page http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1)

I've been gonged by business executives who understand RPBG, but made the best decision for their company.

The business decision to undertake a new product is not just the simple is it a good idea? A company would have to invest several ten thousand dollars to tool up a custom package (not trivial to pass UL mechanical criteria for plugs). I am finessing the plug design by using an existing UL approved plug.

Then the company would have to execute the circuit design. I can't count how many hours I have invested into this design. I am still learning stuff that isn't in books, or wasn't in books back when I matriculated.

Then get UL to approve. I believe UL is flexible, since they already approve the testers that don't work, but they require lubrication with cash especially to approve a novel approach. I expect an interesting discussion about the safety of my approach, and my intention to not print the caveat as stated in the UL spec.

I asked one non-UL test agency to quote on testing my OD-1 and they declined.  :'(

I've been looking at the existing outlet tester technology, and any that depend on the outlet safety ground as a ground reference will be susceptible to being fooled by RPBG (with AC voltage measurements it doesn't matter which end is hot).  I saw one fancy premium tester that included the UL fine print (code for can't detect RPBG i.e. can't detect two wiring faults at the same time. )

IMO the cheap 3 lamp testers should not even be sold... Nobody reads the fine print caveat printed on the back of the cardboard counter card they are sold with. BTW these testers should say "will not detect potentially lethal wiring".

NCVT are your friend.

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 27, 2016, 12:58:45 pm
Oh oh... just changed it again....  :-\

I need to do some more component research but I am now reading 550M insulation resistance, both polarities.  8) 8) I suspect it's higher than that.

I wasted some more time trying to make this work without the touch probe, but still no success.

One more cut...

JR

Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 30, 2016, 11:50:45 am
"I had a dream......".  I had a lucid dream the other night about designing an outlet tester that didn't require a touch contact (external reference). After solving that design problem I fell into a deep sleep... I woke up the next morning, and like every other morning, it doesn't work with simple discrete components.  :'(

It is an unfortunate characteristic of AC voltage/current, that when measuring with a meter relative to the two leads, polarity doesn't matter.  You could swap the two meter leads around and get the exact same reading. This is why the cheap 3-lamp outlet testers are so easily fooled.

RPBG is not the only erroneous reading they make, but perhaps the most hazardous to human safety. I need to test more combinations and put a chart on my OD-1 page. If I was tasked with designing an outlet tester and that 3-lamp approach was the best I could come up with, I'd drop the project and tell my boss that it can't be done.  8)

I don't completely understand why UL approved it, with such a minimal warning notice. I would have made them print a skull and cross bones on the front of the 3-lamp tester housing.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on May 01, 2016, 01:52:36 am
"I had a dream......".  I had a lucid dream the other night about designing an outlet tester that didn't require a touch contact (external reference). After solving that design problem I fell into a deep sleep... I woke up the next morning, and like every other morning, it doesn't work with simple discrete components.  :'(

I have no idea HOW it works, but I have just such an NCVT. I can stab the plastic tip into the hot side of an outlet, let go, and it stays lit.

I have had it for probably 25 years. It was sold by GB (then known as Gardner-Bender). It uses two AA batteries, and I've changed them maybe twice in that time.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 01, 2016, 10:52:27 am
I have no idea HOW it works, but I have just such an NCVT. I can stab the plastic tip into the hot side of an outlet, let go, and it stays lit.
I guess some combination of multiple NCVT and lamps (LEDs) could work (you still need to confirm that an electrical path is present for neutral and ground).
Quote

I have had it for probably 25 years. It was sold by GB (then known as Gardner-Bender). It uses two AA batteries, and I've changed them maybe twice in that time.
My cheaper, NCVT goes off when it gets within a foot of an outlet... In fact I can't remember where I put it so it wouldn't be constantly going off when kept anywhere near my work bench.

Even a NCVT requires a reference to compare the voltage field it detects to. A sensitive enough detector probably uses the batteries as the local reference.

Back about a year ago when I prototyped an automatic relay protected GFCI power drop, I was able to use the safety ground  (basically capacitance to ground), of the products plugged into the power drop to use as a ground reference to detect outlet polarity. That prototype was designed to not even power up if it detected reversed polarity (probably too much safety).

It also measured current flowing in the safety ground lead independently of the GFCI protection and could use that to disconnect power (and safety ground) using a 3 pole relay, to protect against external shock sources that the GFCI alone wouldn't protect against. Many musicians shocked during live events are caught between two different power drops.

I still think the stinger cap GFCI would be a remarkable product, since it would also cover that external fault vector but I don't need to start a new project with UL just yet. 

JR

PS: The OD-1 is pretty sensitive, I think it needs about 20pF of capacitance at the probe to detect (human body ranges between tens and hundreds of pF). I might be able to increase that sensitivity and grab a reference somehow from the plug body, or not. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 10, 2016, 01:37:02 pm
Here we go again... I just ordered the last version PCB ever (again).

I added the high voltage cap in series with my input, so now the insulation resistance @ 500V is off-scale for the fluke (>550M ohm). I made the board slightly larger to improve clearance around exposed mains voltage.

When I get these boards in, I will start swapping out units with my beta testers first, so they are working with the final version.

Then I need to get serious with UL,,, (not looking forward to that). 

another step forward... closer to done.

JR

[edit] I did some more testing and as we would expect the 3-lamp tester does not detect line-neutral reversed polarity. This is not dangerous by itself with most modern equipment, but you would expect an outlet tester to check that.

Curiously I noticed when testing without a safety ground (like most of my house), plugging in the OD-1 and 3 lamp tester into the same outlet at the same time causes the OD-1 to falsely report a hot ground because of the 3 lamp tester creating a current path from line into the floating safety ground. (I saw this before with blown protection devices on an outlet strip, energizing the ground).  [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on May 10, 2016, 04:06:04 pm
Curiously I noticed when testing without a safety ground (like most of my house), plugging in the OD-1 and 3 lamp tester into the same outlet at the same time causes the OD-1 to falsely report a hot ground because of the 3 lamp tester creating a current path from line into the floating safety ground. (I saw this before with blown protection devices on an outlet strip, energizing the ground).

But it still detects a fault; it just misidentifies the fault. That's better than no indication of a fault, or even a false positive (indicating a fault where there is none).
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 10, 2016, 05:21:04 pm
But it still detects a fault; it just misidentifies the fault. That's better than no indication of a fault, or even a false positive (indicating a fault where there is none).
The only fault was that I had a 3 lamp outlet tester plugged in.  8) The OD1 correctly identified too much voltage on the safety ground.

UL allows outlet testers to dump 2mA into ground, i suspect I could tweak the OD-1 to ignore the 3 lamp tester's leakage, but decided not to... that way it can ID bad outlet strips with leaky protection devices and the like (my flaky outlet strip was leaking right around 2mA before I fixed it by clipping out the shorted parts).  I could feel the 2mA from my bad outlet strip, BTW.

I may need to add a note to my instructions about 3-lamp testers. If you have a 3 lamp outlet tester, unplug it, then see how far you can throw it over your back fence. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 13, 2016, 02:32:18 pm
Boards just shipped air mail from China...  ;D

Just ordered another $35 of parts from the parts house...  :(

Death by a thousand cuts....  :o

Hopefully this final version will really be the last one.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 22, 2016, 07:20:39 pm
The OD-1 (ken-o-bee) to end all OD-1s is alive and well...

In the picture I have latest OD-1, plugged into the same outlet as a 3-lamp tester, with RPBG.

While the blue LED (Power) LED is still too bright and washes out the colors on my old digital camera, you can clearly see the red and yellow fault LEDs indicating correctly that both safety ground and neutral are HOT. (Correct)  8)  While the commercial 3-lamp turd, says "all is well" (WRONG)... :-[ :-[ :-[

I updated my OD-1 web page  http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1) with improved art for the outlet schematics and new photo. With the proper 600V cap the input Z still measures >550M but it measured that with a low voltage cap so no surprises there.

I have pretty much run out of things to improve. Time for me to spit or get off the marijuana...(is that how the saying goes?) Actually I'm going to open a Johnny Beer to celebrate. I hand populated 4 of those boards with 28 tiny ass SMD parts on each one. I'm too old to be hand soldering stuff I can barely see with two magnifying glasses. To see the cathode marking on the diodes, I had to look through a third magnifying lens. 

JR

PS: The extra green LED is because I am using two green "ground present" LEDs. My tester thinks bootleg ground is OK. I am using two ground LEDs because UL limits how much current I can dump into ground to 2 mA max and expects a resistive symmetrical load, so using the two green LEDs anti-parallel, I get the max light for the least current and keep it symmetrical. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Tom Roche on May 23, 2016, 05:57:49 pm
The OD-1 (ken-o-bee) to end all OD-1s is alive and well...

In the picture I have latest OD-1, plugged into the same outlet as a 3-lamp tester, with RPBG.

While the blue LED (Power) LED is still too bright and washes out the colors on my old digital camera, you can clearly see the red and yellow fault LEDs indicating correctly that both safety ground and neutral are HOT. (Correct)  8)  While the commercial 3-lamp turd, says "all is well" (WRONG)... :-[ :-[ :-[

I updated my OD-1 web page  http://circularscience.com/home/terms-and-conditions/od-1 (http://circularscience.com/home/terms-and-conditions/od-1) with improved art for the outlet schematics and new photo. With the proper 600V cap the input Z still measures >550M but it measured that with a low voltage cap so no surprises there.

I have pretty much run out of things to improve. Time for me to spit or get off the marijuana...(is that how the saying goes?) Actually I'm going to open a Johnny Beer to celebrate. I hand populated 4 of those boards with 28 tiny ass SMD parts on each one. I'm too old to be hand soldering stuff I can barely see with two magnifying glasses. To see the cathode marking on the diodes, I had to look through a third magnifying lens. 

JR

PS: The extra green LED is because I am using two green "ground present" LEDs. My tester thinks bootleg ground is OK. I am using two ground LEDs because UL limits how much current I can dump into ground to 2 mA max and expects a resistive symmetrical load, so using the two green LEDs anti-parallel, I get the max light for the least current and keep it symmetrical.

I hope the rest of the process bringing this to market goes well for you, JR.  I'm eagerly awaiting the opportunity to buy one and know others who would be interested as well.
Title: Re: brain storm an optimal human safety system for back line
Post by: Jordan Wolf on May 23, 2016, 08:08:13 pm
I hope the rest of the process bringing this to market goes well for you, JR.  I'm eagerly awaiting the opportunity to buy one and know others who would be interested as well.
I, too, am eager to buy one.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 23, 2016, 08:42:05 pm
Thanx guys I just submitted a RFQ to UL for testing but fear I will get sticker shock (I'm cheap).
====
I tried to call the company that makes the plug housing I am using to suggest a partnership and the switchboard wouldn't let me talk to a product manager. Instead he said he was sending me to the "new ideas"  girl (code for see ya), who turned out to be an un-named voice mailbox... probably erased already.

I may just have to go outlaw... I know i can pass the UL spec, just don't know about jumping through all the extra hoops.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Helmke on May 24, 2016, 09:58:42 am
I, too, am eager to buy one.

Me too.
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on May 24, 2016, 11:29:46 am
Me too.
I've expressed my desire before.  Fingers are still crossed.


Let's put a different twist on the next question.
In other posts, there was discussion of a stinger cap somewhere in the ground line, possibly a stage-stringer.
How does your tester respond should the stinger be in place between the wall power and the tester?  I can see maybe running a stringer with a stinger cap and plugging the tester into the stringer along the way.  Would your tester see the ground potential the same?
frank



Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 24, 2016, 12:16:13 pm
I've expressed my desire before.  Fingers are still crossed.


Let's put a different twist on the next question.
In other posts, there was discussion of a stinger cap somewhere in the ground line, possibly a stage-stringer.
How does your tester respond should the stinger be in place between the wall power and the tester?  I can see maybe running a stringer with a stinger cap and plugging the tester into the stringer along the way.  Would your tester see the ground potential the same?
frank

Why speculate when I can empirically determine the result?

Yes, a 0.15uF stinger cap in series with safety ground still indicates a good ground present with both the POS 3-lamp tester, and my OD-1.

0.15uF is the johnny approved stinger cap value, large enough to trip a GFCI, but small enough to prevent harm to humans. If you want to really do it right use a Y2 rated cap.

digikey has onesies for $3.50  http://www.digikey.com/product-detail/en/kemet/PME271YE6150KR30/399-12419-ND/5730910 (http://www.digikey.com/product-detail/en/kemet/PME271YE6150KR30/399-12419-ND/5730910)
 
JR

PS: I really like the idea of stinger cap GFCI power drop and will discuss this with UL if I ever engage a human there. First things first...
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on May 24, 2016, 09:41:37 pm
Why speculate when I can empirically determine the result?

Yes, a 0.15uF stinger cap in series with safety ground still indicates a good ground present with both the POS 3-lamp tester, and my OD-1.

0.15uF is the johnny approved stinger cap value, large enough to trip a GFCI, but small enough to prevent harm to humans. If you want to really do it right use a Y2 rated cap.

digikey has onesies for $3.50  http://www.digikey.com/product-detail/en/kemet/PME271YE6150KR30/399-12419-ND/5730910 (http://www.digikey.com/product-detail/en/kemet/PME271YE6150KR30/399-12419-ND/5730910)
 
JR

PS: I really like the idea of stinger cap GFCI power drop and will discuss this with UL if I ever engage a human there. First things first...
Thanks, JR.  Good luck finding a human...
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on May 25, 2016, 01:44:45 pm
I actually talked to a human from UL today so progress,,, I guess asking them for a quote triggered a response.  ;D

The guy I talked to wasn't very technical. He said they wanted to classify my product as lab equipment? I don't agree but he is setting up a conference call with some more technical people so we can move this forward.

He sounded receptive to accepting the already approved plug as an UL approved sub-assembly, so if true that could reduce my testing costs.

Another step forward.  8)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 08, 2016, 02:42:02 pm
As I feared I received the quote for UL to begin testing my OD-1. $10,600 to open a file. Plus more charges associated with testing.

I need to soak this in beer for a while, before cutting that check... Lets see, if i sell them for $100 ea I only need to sell a couple hundred. :-[ but that's too expensive. I wouldn't pay that.   

Before I go down this expensive rabbit hole, I need to ask this community again for more possible leads that I should approach to produce these, instead of me.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: frank kayser on June 08, 2016, 04:30:54 pm
As I feared I received the quote for UL to begin testing my OD-1. $10,600 to open a file. Plus more charges associated with testing.

I need to soak this in beer for a while, before cutting that check... Lets see, if i sell them for $100 ea I only need to sell a couple hundred. :-[ but that's too expensive. I wouldn't pay that.   

Before I go down this expensive rabbit hole, I need to ask this community again for more possible leads that I should approach to produce these, instead of me.

JR
Ouch!  Some type of croud-sourcing like Kickstarter?  SharkTank?  West Texas Investors Club?
frank
Title: Re: brain storm an optimal human safety system for back line
Post by: Tom Roche on June 08, 2016, 06:06:01 pm
As I feared I received the quote for UL to begin testing my OD-1. $10,600 to open a file. Plus more charges associated with testing.

I need to soak this in beer for a while, before cutting that check... Lets see, if i sell them for $100 ea I only need to sell a couple hundred. :-[ but that's too expensive. I wouldn't pay that.   

Before I go down this expensive rabbit hole, I need to ask this community again for more possible leads that I should approach to produce these, instead of me.

JR

Wow, that seems especially costly to test such a small device.  Will UL provide a breakdown of the costs or is it largely a "pay to play" thing?  Have you considered checking with one or more of the competing Nationally Recognized Testing Laboratories?  Granted, the other NRTLs don't enjoy the name recognition that UL does, but it might save you a few pennies.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 08, 2016, 06:15:09 pm
Ouch!  Some type of croud-sourcing like Kickstarter?  SharkTank?  West Texas Investors Club?
frank
Sorry if i wasn't clear... I actually have that much capital I could spend, but I question how wise that would be (I'm old and tired).  The only thing worse than spending my own money that way is spending other people's money that way.

I don't literally want a business partner, or investor.. I've been there and done that. I don't want to start a(nother) company from scratch just to merchandise this.

I have developed a product idea, and proved that the concept works. I have even satisfied myself that the design "could" be UL approved, but then what? I would have to manufacture at least few hundred to get economic production volume, then develop distribution to sell these through, and then manage that distribution to gat paid in time to pay for building the next batch, etc... I have done the small company rat race before and in my judgement this is too much overhead for one low priced SKU that can't support that much sales marketing, distribution overhead, by itself and still remain cost effective.

This needs to be some established test equipment company's Nth piece of test equipment added to an existing line of testers, that they can sell through existing distribution.

Even better they need to tool up a custom package which will match the rest of their product line (another couple $10k).

To be clear, I am NOT looking for capital investment in me, I am looking for a company already in the business that could benefit from investing in their own new outlet tester product (that actually works). I am willing to share the technology, while if I am willing to give it away completely free, it will by definition be worth nothing. I am not greedy, and really believe in this product, so am motivated to work with almost anybody. 

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 08, 2016, 06:31:01 pm
Wow, that seems especially costly to test such a small device.  Will UL provide a breakdown of the costs or is it largely a "pay to play" thing?  Have you considered checking with one or more of the competing Nationally Recognized Testing Laboratories?  Granted, the other NRTLs don't enjoy the name recognition that UL does, but it might save you a few pennies.
I do not want to flame UL they are a large established organization doing good work. I knew going in that this would be expensive. The quotation reads like $10.6k + travel and + yadda yadda... I need to talk to other companies who have gone through this process to get an idea of how much the yadda yadda is, or could be in practice.

UL is never going to be cheap because they are where the buck stops, when it comes to human safety. When that musician got electrocuted by a RPBG outlet while playing Peavey guitars, UL was with Peavey in court as expert witnesses defending that the Peavey products were safe.   

JR

PS: I did approach a cheaper testing laboratory and they declined to even quote on my project. Testing outlet testers is probably not a high volume business for UL.
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on June 09, 2016, 01:39:29 am
I do not want to flame UL they are a large established organization doing good work. I knew going in that this would be expensive. The quotation reads like $10.6k + travel and + yadda yadda... I need to talk to other companies who have gone through this process to get an idea of how much the yadda yadda is, or could be in practice.

UL is never going to be cheap because they are where the buck stops, when it comes to human safety. When that musician got electrocuted by a RPBG outlet while playing Peavey guitars, UL was with Peavey in court as expert witnesses defending that the Peavey products were safe.   

JR

PS: I did approach a cheaper testing laboratory and they declined to even quote on my project. Testing outlet testers is probably not a high volume business for UL.

The U is for Underwriters, an insurance term.  I never quite thought of the connection until you made this post so I went and read the history of UL and I didn't see any ties to the insurance industry.

A curiosity. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 09, 2016, 09:47:17 am
The U is for Underwriters, an insurance term.  I never quite thought of the connection until you made this post so I went and read the history of UL and I didn't see any ties to the insurance industry.

A curiosity.
Worked for fire insurance industry to test electrical devices, insulation flammability, etc.
http://www.ul.com/aboutul/history/ (http://www.ul.com/aboutul/history/)
History according to them.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on June 09, 2016, 10:50:18 am
Underwriters Laboratories Inc. was founded in 1894 by William Henry Merrill. Early in his career as an electrical engineer in Boston, a 25-year-old Merrill was sent to investigate the World Fair’s Palace of Electricity. Upon seeing a growing potential in his field, Merrill stayed in Chicago to found Underwriters Laboratories.
https://en.wikipedia.org/wiki/UL_%28safety_organization%29

Now it all makes sense.
Title: Re: brain storm an optimal human safety system for back line
Post by: Mark Cadwallader on June 09, 2016, 01:34:42 pm
When you remember that the NFPA (National Fire Protection Association), the author of the NEC, is an organization created by the causualty insurance (fire insurance) industry, it makes even more sense.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 23, 2016, 02:39:43 pm
Is anybody familiar with this guy...? Hubbell 5200
(http://www.newark.com/productimages/standard/en_US/3763580.jpg)
I'd buy one to take apart but they're like $65  ??? ???

Looks like an LED version of the 3 lamp tester.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Tom Roche on June 23, 2016, 02:52:11 pm
Is anybody familiar with this guy...? Hubbell 5200
(http://www.newark.com/productimages/standard/en_US/3763580.jpg)
I'd buy one to take apart but they're like $65  ??? ???

Looks like an LED version of the 3 lamp tester.

JR

Probably nothing you didn't find already, but there's this: http://ecatalog.hubbell-wiring.com/press/catalog/Z-3.pdf
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on June 23, 2016, 04:32:36 pm
When I moved back to CA in 1980 I interviewed at UL.  They showed me around their "lab".  Aside from a flame tunnel most of the set ups were pretty cobby.  They had a bunch of electric weedwackers sitting on a wooden bench with zip-ties around the triggers and clamps they'd fabricated locking the rotors.  I asked how long they left them like that and was told something like 12 hours.  I figured anyone who held the trigger of a weedwhacker that wasn't doing anything for 12 hours might not be worth protecting.  There was another portable stair thing like you see at Home Depot with a bowling ball hanging from a rope tied to the top.  They'd epoxied an eye bolt in one of the finger holes.  There were laundry marker stripes on one of the hand rails and masonite attached to the front.  They would set a CRT (TV or computer monitor) on a table, pull the bowling ball back to one of the marks they had, let go and jump behind the masonite.  Pretty much everything there was like that.  They were really big on advanced degrees for their staff so that there was some weight behind their findings and reports.  Having dealt with various certification labs over the years since I've been similarly unimpressed.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 23, 2016, 09:26:42 pm
The value in UL approval is not that they are smarter engineers than me... it's that it will keep the lawyers in check.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Kirby on June 24, 2016, 05:59:15 pm
The value in UL approval is not that they are smarter engineers than me... it's that it will keep the lawyers in check.

JR
Understood.  That was why they needed everyone on the staff to have a PhD.  So the lawyers could impress juries.

Probably best if you can get Klein or GC interested in it.  Or at least distributing it in volume.  Most of the large contract manufacturers have pretty serious compliance labs.  And will do the testing for a volume order.  I'm flying out tonight to China and Quanta.  They have compliance labs on each of their manufacturing campuses.  Wouldn't carry as much weight with a US jury as UL but would take it off of your shoulders. 
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on June 24, 2016, 10:52:07 pm
I wonder if any actually have a UL certified lab? I visited Milbank in Kansas City a while ago and and they did ther own UL testing.  Fairly sophisticated compared to observations from an earlier post.  Of course, they compined their testing lab with R&D- makes sense since both functions would require similar testing capabilites.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 25, 2016, 12:40:58 am
I wonder if any actually have a UL certified lab? I visited Milbank in Kansas City a while ago and and they did ther own UL testing.  Fairly sophisticated compared to observations from an earlier post.  Of course, they compined their testing lab with R&D- makes sense since both functions would require similar testing capabilites.
I am not sure I understand the question. At Peavey we had our own in house agency approval dept. with test equipment to test all kinds of stuff (lots of RF sniffers etc)... In fact i am still in touch with the Peavey in house engineer, in case I need that kind of advice.

It is logical for large companies to do their own testing.

I tried to get a third party test agency to quote my outlet tester and they declined.

It's just time and money....

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on June 30, 2016, 05:11:21 pm
Is anybody familiar with this guy...? Hubbell 5200
(http://www.newark.com/productimages/standard/en_US/3763580.jpg)
I'd buy one to take apart but they're like $65  ??? ???

Looks like an LED version of the 3 lamp tester.

JR

Bump, no one has seen one of these?

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 01, 2016, 02:16:09 pm
Bump, no one has seen one of these?

JR

How many do you want? I'll send an inquiry to Hubble and see if they'll send each of us a few to experiment on.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 01, 2016, 02:43:36 pm
How many do you want? I'll send an inquiry to Hubble and see if they'll send each of us a few to experiment on.
If you can get your hands on one, just test it for RPBG.  My suspicion is that it is just an LED version of the old neon lamp outlet testers, so will act the same wrt RPBG, but i don't know without testing. I am too cheap to pay the going price for what I think is inside there.

They look like they just built their tester into one of their standard plugs. I am more interested if they are doing something different, but their test table looks similar.

I probably need to talk to them, let me know if you raise somebody there who knows about the product. (Years ago I lived one town over from where they are located in CT).

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Frank DeWitt on July 03, 2016, 03:24:31 pm
Now idea how, or even if.
From Amazon
5.0 out of 5 starsThis has become my favorite quick circuit checker
By Alak on March 5, 2016
Worked two to three rock shows a week at a major venue. The house electricians wired a power distribution panel. The panel was used for an entire year by visiting attractions. Each time the road electrician would take his circuit tester out and found no problems. A year into the panels use, a visiting electrician plugged his Hubbell 5200 in and found the panel was miss wired. After removing the cover, sure enough. The neutral and ground were reversed. This has become my favorite quick circuit checker.
https://www.amazon.com/Hubbell-Wiring-Systems-Straight-Grounding/dp/B000N9L598
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 03, 2016, 03:56:40 pm
Now idea how, or even if.
From Amazon
5.0 out of 5 starsThis has become my favorite quick circuit checker
By Alak on March 5, 2016
Worked two to three rock shows a week at a major venue. The house electricians wired a power distribution panel. The panel was used for an entire year by visiting attractions. Each time the road electrician would take his circuit tester out and found no problems. A year into the panels use, a visiting electrician plugged his Hubbell 5200 in and found the panel was miss wired. After removing the cover, sure enough. The neutral and ground were reversed. This has become my favorite quick circuit checker.
https://www.amazon.com/Hubbell-Wiring-Systems-Straight-Grounding/dp/B000N9L598
Hubbell makes no such claim about being able to detect neutral- ground reversed.
(http://www.hubbellcatalog.com/wiring/images/circuit_tester_illustration.GIF)
From a different amazon review
Quote
"Although this is a super well made (albeit pricey) tester, it has the same failing as most three prong testers. There are wiring errors that can't be detected by this - or any other three prong tester."

That is my suspicion too (doesn't detect RPBG), but until i get hands on I can't say that.

If anything they may be yet another candidate for my technology.


JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 03, 2016, 07:59:36 pm
Now idea how, or even if.
From Amazon
5.0 out of 5 starsThis has become my favorite quick circuit checker
By Alak on March 5, 2016
Worked two to three rock shows a week at a major venue. The house electricians wired a power distribution panel. The panel was used for an entire year by visiting attractions. Each time the road electrician would take his circuit tester out and found no problems. A year into the panels use, a visiting electrician plugged his Hubbell 5200 in and found the panel was miss wired. After removing the cover, sure enough. The neutral and ground were reversed. This has become my favorite quick circuit checker.
https://www.amazon.com/Hubbell-Wiring-Systems-Straight-Grounding/dp/B000N9L598

There's no simple way to find swapped neutral and ground wiring since you need a secondary ground reference PLUS be able load the circuit with enough amperage to create a measurable voltage drop in the lines. I'm sure their 5200 tester can't do this. In fact, I've never seen a product (no matter how expensive) that can detect a swapped ground and neutral automatically.

One thing that a swapped G-N does do is create a really big ground loop current that varies with the load. And that can create a variable hum in a sound system with the pin-1 problem. Don't get me started on a discussion about GLID (Ground Loop Inter=modulation Distortion) since you all think I'm crazy. But I'm going to build a demonstration of the GLID phenomenon that I believe contributes to "fuzzy bass" in sound systems with swapped G-N wiring in their power distro.
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on July 03, 2016, 11:45:16 pm
There's no simple way to find swapped neutral and ground wiring since you need a secondary ground reference PLUS be able load the circuit with enough amperage to create a measurable voltage drop in the lines. I'm sure their 5200 tester can't do this. In fact, I've never seen a product (no matter how expensive) that can detect a swapped ground and neutral automatically.


People have a tendency to not think through what is actually happening with a ground and neutral.  Ultimately, they are 2 wires with different purposes that eventually connect to the same place at the service.  Yes, with a load you can see a voltage drop-but it will drop on which ever wire the load is connected to-whether it is the ground or the neutral.  If you load an adjacent receptacle on the same circuit, you might be able to tell that the 2 receptacles are wired the same -or different, but it would be difficult to tell which one is right.  A bootleg ground would be relatively easy to see, as both the neutral and the ground pin on the receptacle would see the same voltage drop.

There is nothing magical about neutrals and grounds-it is simple physics and ohms law applies equally to each circuit.  If you assume that the building is wired mostly correctly and you are dealing with a circuit fed from subpanel and there is a significant load on the subpanel at the time of the test, in theory, the wire whose potential is closer to the hot should be the neutral-since neutral feeding the subpanel would have some voltage drop on it.

There are simply too many unknown parameters when all you are doing is looking at the face of an edison receptacle and trying to decide of the ground and neutral are reversed.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 04, 2016, 01:35:11 am
For human safety ground and neutral reversed are a secondary risk.

Hum is a cosmetic complaint that doesn't kill people.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 04, 2016, 02:17:36 pm
For human safety ground and neutral reversed are a secondary risk.

Hum is a cosmetic complaint that doesn't kill people.

JR

But my position is that ground loop hum makes musicians and technicians do stupid things, such as cutting off the ground pins in the power cord or using a $1 ground adapter from Lowes. That's when it gets dangerous. 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 04, 2016, 02:31:14 pm
But my position is that ground loop hum makes musicians and technicians do stupid things, such as cutting off the ground pins in the power cord or using a $1 ground adapter from Lowes. That's when it gets dangerous.
They make DIY testers (injecting a 60Hz current into ground) to help identify poorly designed old gear with pin 1 problems. If you can't fix them, they should be retired.

JR
  [edit]   http://pin1problem.com/as032.pdf (http://pin1problem.com/as032.pdf)  here is a link to a Jensen paper on how to make a pin one tester.    [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: Mike Sokol on July 04, 2016, 06:18:30 pm
They make DIY testers (injecting a 60Hz current into ground) to help identify poorly designed old gear with pin 1 problems. If you can't fix them, they should be retired.

JR
  [edit]   http://pin1problem.com/as032.pdf (http://pin1problem.com/as032.pdf)  here is a link to a Jensen paper on how to make a pin one tester.    [/edit]

IMHO: My pin-1 tester is a better test since it uses a Wassco Glo-Melt 30-amp/3-volt variac iso-transformer. I can vary the ground loop voltage from 0 to 3 volts and monitor how much current is being injected into pin-1 via a clamp-on ammeter while listening to how much hum is produced. That way you can hear how well different hum reduction technologies work.

My problem with the Jensen test on the attached paper is that there's no 50 mA current limit in real world conditions. My empirical data shows around 1 ampere of current per volt of ground-loop voltage difference, so it's pretty easy to see 2 or 3 amperes of ground loop current on pin-1 if there's 2 or 3 volts ground loop voltage difference. I've personally measured 5 volts ground loop voltage, and I'm sure it had hundreds of amperes of current behind it since it was an industrial building.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 04, 2016, 07:51:04 pm
Do whatever floats your boat...

I added the link for sound guys to do an in their own shop test, for almost no cost to identify pin 1 problem gear (so they can retire it).

UL does not require ground bond integrity for XLR pin one***, or they would already test it at 50A :o .

If you fry some traces you are on your own.

JR

*** I had one simple couple watt fixed install amp with screw terminal audio in/out , where the audio low was labelled ground (oops). ::)  UL ground bond testing blew that trace right off my PCB... I could have passed UL by removing the word "ground" from the chassis legend, but instead I had my PCB guy beef up the PCB trace. 8) 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 08, 2016, 05:46:00 pm
As I mentioned about a month ago I am very apprehensive about being able to break even after costs to get my outlet tester approved, unless i could charge some ridiculous high price each, or sell truck loads of them. Since neither of those are obvious outcomes I put my UL approval submission on hold, but i asked UL if I could get answers to a few specific questions.

Today I got a call from a clerical type from UL, (not an engineer) and he said I should be able to get answers. There might be some charges if bench time was involved.

My two questions are.

#1 does my high impedance mosfet input (>550M) count as fully insulated in UL's eyes. A hurdle my outlet tester would need to clear before approval.

#2 can a stinger cap be used in place of safety ground inside a GFCI power drop, with adequate labelling warning that it is not ground bonded.

Not sure what I will do with these answers, but I'd know more than I know now.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Jonathan Johnson on July 15, 2016, 06:37:03 pm
For what it's worth, this is the most active thread on PSW, with over 500 replies. Almost 41,000 views (not quite the most views). Guess that means that there's a fair amount of interest in this topic, though a lot of the replies and views could likely be attributed to a few very active members.

It started out as a brainstorm for a "smarter" GFCI-type device, and evolved into developing a smarter outlet tester -- not too far off-topic. Thanks, JR! It's been an interesting study.

And there are a couple of other active threads here talking about stinger caps and GFCIs. It's all good discussion, and I have to say, at a higher and more scientific/practical level than a lot of the forums out there in the real world.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on July 15, 2016, 06:43:02 pm
For what it's worth, this is the most active thread on PSW, with over 500 replies. Almost 41,000 views (not quite the most views). Guess that means that there's a fair amount of interest in this topic, though a lot of the replies and views could likely be attributed to a few very active members.

It started out as a brainstorm for a "smarter" GFCI-type device, and evolved into developing a smarter outlet tester -- not too far off-topic. Thanks, JR! It's been an interesting study.

And there are a couple of other active threads here talking about stinger caps and GFCIs. It's all good discussion, and I have to say, at a higher and more scientific/practical level than a lot of the forums out there in the real world.
I am still waiting for UL to get back to me on my 2 questions.

If they would approve a stinger cap ground GFCI power drop version, that could be a nice niche product for the SR industry.

If we (or someone) did a dedicated back-line version the wire could be specified appropriately (that does not seem like the hard part to me).

JR
 
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on August 18, 2016, 04:44:28 pm
I heard back from UL about my two questions and they suggest between $1400 and $2800 for either a half day or full day of work.  I asked again for more clarification, since i am asking pretty much hypothetical questions that should require no bench testing.

The stinger cap GFCI power drop question would actually require me first buying the UL standard for that (UL 943 at $800-$2000) so I could read it to make intelligent comments about a proposed change.

I appreciate the monetary value of a written opinion from UL, but this hobby is getting expensive.

JR 

[edit] had a conference call with UL and a plan may be coming together... more later... [/edit]
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on September 21, 2016, 12:15:37 pm
UL still hasn't answered my last question (about what device they use for insulation resistance testing). The spec calls for using a "magnetomegometer" with 500V open circuit voltage. Since i can not find any such type of test equipment in google I asked for clarification. I am not going to pay them to perform a test that I am not confident I will pass.  8)

FWIW a "Megnetometer" is a device for measure magnetic fields (flux) and would never have an open circuit voltage. A "mego(hm)meter" is a common high resistance ohm meter that could have a 500V open circuit voltage. OTOH a magneto(-)megometer (hyphen added by me) sounds like a real thing, a hand crank magneto to provide a megohmmeter's voltage source.

Since it has been weeks since I asked them with no answer, I am losing interest. I do not want to submit based on my best guess.

I am ready to abandon making and selling these myself. Also I have had no success developing a constructive partnership with an existing manufacturer. As promised I am publishing the technology so any and all can use it for free. I never did this for money.

(http://johnhroberts.com/images/od1.bmp)

http://www.johnhroberts.com/OD1.htm (http://www.johnhroberts.com/OD1.htm)

I have published a written description of how this works (at link above). I invite any circuit knowledgeable guys out there to check this out and tell me if there are still parts of the circuit that are not clear. Trust me, some of this is obvious but some is pretty obscure, especially how the local reference actually works.. I didn't figure it out for several months into the development. There is a difference between making something that works, and understanding how it works.  :-\

Please share this with anyone who might have interest. I expect the technology has multiple human safety applications beyond outlet testers.

JR

PS: This new OD-1 web page is a work in process and I will add more information like a comprehensive BOM, etc.

PPS: I may finish building and auction off the handful of these I have to recoup at least part of my out of pocket spending. Caveat emptor not UL approved.  8)
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 21, 2018, 11:14:50 am
My OD-1 is still sitting collecting dust as I have given up on getting a commercial partner or throwing more money down the UL black hole.

A friend recently shared a new product he saw... https://www.lessemf.com/ground.html#452 (https://www.lessemf.com/ground.html#452)(https://lessemf.com/images/a452.jpg)

I haven't bothered to dissect one but it appears to combine a common 3 lamp tester (with known inability to detect RPBG) with a touch probe that turns on a LCD hazard warning if safety ground is energized.

Of course I like the idea using a touch probe to have an external reference, but I question the safety or UL approvability of such a design.  My interpretation of the UL spec requires a >100M insulation resistance @500V  for any exposed metal (like a touch contact). I was able to deliver off scale >500M.  8)

Further feeding my suspicion about them and their UL aspirations, they have boldly marked the tester with CE  ::) ::) From an american company, selling a product only to americans, that only plugs into american outlets.

FWIW they could have accomplished the hot safety ground indicator with a neon lamp, but again that won't deliver >100M @ 500V insulation resistance (like mine does).

I am not recommending this just sharing, while it is cheap enough I would just suggest buying a simple neon lamp probe, even cheaper and just as effective.  FWIW this neon lamp screwdriver probe claims to be UL listed and retails for <$5
http://www.morrisproducts.com/pc_product_detail.asp?key=1962950B5A4A4EB28E1DABB310CA4228 (http://www.morrisproducts.com/pc_product_detail.asp?key=1962950B5A4A4EB28E1DABB310CA4228)  (http://www.morrisproducts.com/images/59040_n.jpg)

If UL is willing to approve(list?) this screwdriver a cheap 4 lamp tester that actually works seems UL possible?

I just don't have the energy to wrestle with UL.

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Scott Holtzman on April 21, 2018, 06:26:15 pm
My OD-1 is still sitting collecting dust as I have given up on getting a commercial partner or throwing more money down the UL black hole.

A friend recently shared a new product he saw... https://www.lessemf.com/ground.html#452 (https://www.lessemf.com/ground.html#452)(https://lessemf.com/images/a452.jpg)

I haven't bothered to dissect one but it appears to combine a common 3 lamp tester (with known inability to detect RPBG) with a touch probe that turns on a LCD hazard warning if safety ground is energized.

Of course I like the idea using a touch probe to have an external reference, but I question the safety or UL approvability of such a design.  My interpretation of the UL spec requires a >100M insulation resistance @500V  for any exposed metal (like a touch contact). I was able to deliver off scale >500M.  8)

Further feeding my suspicion about them and their UL aspirations, they have boldly marked the tester with CE  ::) ::) From an american company, selling a product only to americans, that only plugs into american outlets.

FWIW they could have accomplished the hot safety ground indicator with a neon lamp, but again that won't deliver >100M @ 500V insulation resistance (like mine does).

I am not recommending this just sharing, while it is cheap enough I would just suggest buying a simple neon lamp probe, even cheaper and just as effective.  FWIW this neon lamp screwdriver probe claims to be UL listed and retails for <$5
http://www.morrisproducts.com/pc_product_detail.asp?key=1962950B5A4A4EB28E1DABB310CA4228 (http://www.morrisproducts.com/pc_product_detail.asp?key=1962950B5A4A4EB28E1DABB310CA4228)  (http://www.morrisproducts.com/images/59040_n.jpg)

If UL is willing to approve(list?) this screwdriver a cheap 4 lamp tester that actually works seems UL possible?

I just don't have the energy to wrestle with UL.

JR

John - did you look at their website?  The Faraday gloves seem dubious, maybe I just don't understand the application.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 21, 2018, 10:04:20 pm
John - did you look at their website?  The Faraday gloves seem dubious, maybe I just don't understand the application.
Um no... I told you tinfoil hat crowd.....  ::)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Stephen Swaffer on April 22, 2018, 03:01:54 pm

Further feeding my suspicion about them and their UL aspirations, they have boldly marked the tester with CE  ::) ::) From an american company, selling a product only to americans, that only plugs into american outlets.


And even if  it were from a European country, my understanding is the CE mark is essentially a self policing standard that requires no testing and is specifically not intended to imply meeting any safety standards.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 22, 2018, 03:25:43 pm
And even if  it were from a European country, my understanding is the CE mark is essentially a self policing standard that requires no testing and is specifically not intended to imply meeting any safety standards.
CE is self reporting, not self policing, but it has little teeth against a distant manufacturer.

Quote from: WWW
CE marking is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area (EEA). The CE marking is also found on products sold outside the EEA that are manufactured in, or designed to be sold in, the EEA.

A US mfr selling products into EU falsely claiming to meet EU standards, puts the EU distributor and/or dealers at risk of legal consequences. 

The EU safety standards are now a harmonized version of the old safety standards that were a huge PIA meeting the requirements and getting approval from every different country. Back in the day they kind of standardized on Germany and Norway testing (IIRC?) but still a huge PIA, now is betta.

But of course that US made tester for domestic outlets with a CE mark is yet another IQ test for ignorant consumers.  ::)

That said I have seem non-UL SKUs sold by web merchants that should know better but that's another story for another day.
-------------

To bring this slightly back on topic if that neon probe screwdriver is UL listed as they claim, that suggests to me that it would possible to get UL to bless a cheap and dirty 4 lamp outlet tester, that adds one more lamp to the cheaper than dirt 3 lamp testers that don't work (to detect RPBG). A fourth neon bulb inside with a series resistor between the safety ground and an external tough probe would light if the safety ground was energized and human touched the probe. Of course this involves a much lower than 100M insulation resistance (like that screwdriver probe) but only low single digit mA so no risk to human safety.

This tells me that for less than $1 BOM hit, the 3 lamp testers could become a 4 lamp tester that actually works.

Now how do I get in touch with that chinese manufacturer who makes all these?  :o

JR 
Title: Re: brain storm an optimal human safety system for back line
Post by: Lyle Williams on April 22, 2018, 03:31:11 pm
... and quietly, with nobody really noticing, the unseen hand of the regulator made the cheap chinese tester superior to the American one.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 22, 2018, 03:41:41 pm
... and quietly, with nobody really noticing, the unseen hand of the regulator made the cheap chinese tester superior to the American one.

The 3 lamp tester may have originally been US designed it is now owned by chinese manufacturing.

I wish UL was more proactive about human safety, but they see their job as more of a service sold to manufacturers, thus their approval of the 3 lamp testers (after adding some fine print caveats) that IMO are dangerous.

Maybe after a cheap 4 lamp tester comes into existence they might man up and outlaw the 3 lamp testers. (nah)  ::)

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on April 23, 2018, 09:11:02 am

Now how do I get in touch with that chinese manufacturer who makes all these?  :o

JR
Um, you already know how JR.
Build one and start selling it for 20 bucks, they will engineer(photocopy) one, and build them for 2 bucks. Delivered.  :(
Title: Re: brain storm an optimal human safety system for back line
Post by: Dave Garoutte on April 23, 2018, 03:34:30 pm

I wish UL was more proactive about human safety, but they see their job as more of a service sold to manufacturers, thus their approval of the 3 lamp testers (after adding some fine print caveats) that IMO are dangerous.

JR

Aren't they making sure the TESTER itself is safe?  Not whether it's test is useful in checking for safe outlets?
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 23, 2018, 06:04:17 pm
Aren't they making sure the TESTER itself is safe?  Not whether it's test is useful in checking for safe outlets?
Perhaps but a consumer that sees UL approval on an outlet tester probably ASSumes the tester would catch unsafe wiring.  I would.

JR
Title: Re: brain storm an optimal human safety system for back line
Post by: Chris Hindle on April 23, 2018, 06:37:04 pm
Perhaps but a consumer that sees UL approval on an outlet tester probably ASSumes the tester would catch unsafe wiring.  I would.

JR
I dunno JR.
I see UL, I presume the "thing" is safe to plug in. NOT that it does the job I imagine it is supposed to do....
Chris.
Title: Re: brain storm an optimal human safety system for back line
Post by: John Roberts {JR} on April 27, 2018, 11:34:15 am
Since a picture is worth a thousand words, here is a picture of my cheap lamp tester with a neon lamp hanging off the ground lead.

When plugged into an intentional RPBG I see the neon lamp illuminate dimly (by my finger) when I touch it... The 100k series resistor probably limits the current to well less than 1mA, so I could go several steps brighter.

I could use this dim light from very low current to trigger the gate of an optical device to light a much brighter lamp, but that would defeat my <$1 BOM cost increase.

JR

PS Don't try this at home,  :o  just carry a cheap neon lamp probe.