ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3 4 ... 55   Go Down

Author Topic: brain storm an optimal human safety system for back line  (Read 80682 times)

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3161
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: brain storm an optimal human safety system for back line
« Reply #10 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
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1981
Re: brain storm an optimal human safety system for back line
« Reply #11 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.
« Last Edit: December 13, 2014, 01:02:52 am by Stephen Swaffer »
Logged
Steve Swaffer

Lyle Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1327
Re: brain storm an optimal human safety system for back line
« Reply #12 on: December 13, 2014, 03:34:07 am »

Wireless mic and guitar pack.  Performer wears rubber soled shoes as a backup.  :-)
Logged

Steve M Smith

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3037
  • Isle of Wight - England
Re: brain storm an optimal human safety system for back line
« Reply #13 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.
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3161
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: brain storm an optimal human safety system for back line
« Reply #14 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

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)
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Steve Bradbury

  • Newbie
  • *
  • Offline Offline
  • Posts: 47
Re: brain storm an optimal human safety system for back line
« Reply #15 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.
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 15908
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #16 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?
Logged
On the internet people tell you everything "they" know, not the answer to "your" question.....  http://circularscience.com/

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 15908
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #17 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.
Logged
On the internet people tell you everything "they" know, not the answer to "your" question.....  http://circularscience.com/

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 15908
  • Hickory, Mississippi, USA
    • Resotune
Re: brain storm an optimal human safety system for back line
« Reply #18 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
Logged
On the internet people tell you everything "they" know, not the answer to "your" question.....  http://circularscience.com/

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1981
Re: brain storm an optimal human safety system for back line
« Reply #19 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?   
Logged
Steve Swaffer
Pages: 1 [2] 3 4 ... 55   Go Up
 


Page created in 0.072 seconds with 21 queries.