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Author Topic: brain storm an optimal human safety system for back line  (Read 103819 times)

Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #370 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.
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Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #371 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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #372 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.  ::)
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #373 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
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #374 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
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #375 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
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Mark Cadwallader

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Re: brain storm an optimal human safety system for back line
« Reply #376 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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #377 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.  :-[ :-[ :-[
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #378 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    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

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.
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

TJ (Tom) Cornish

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Re: brain storm an optimal human safety system for back line
« Reply #379 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.
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Re: brain storm an optimal human safety system for back line
« Reply #379 on: November 04, 2015, 10:00:36 am »


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