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Author Topic: brain storm an optimal human safety system for back line  (Read 95593 times)

Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #530 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  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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #531 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) 
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #532 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
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Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #533 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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #534 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
 
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #535 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]
« Last Edit: August 22, 2016, 08:04:15 pm by John Roberts {JR} »
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #536 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://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)
« Last Edit: September 22, 2016, 01:51:32 pm by John Roberts {JR} »
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #537 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

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 

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 
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Scott Holtzman

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Re: brain storm an optimal human safety system for back line
« Reply #538 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

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 

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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #539 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
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