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Author Topic: brain storm an optimal human safety system for back line  (Read 104381 times)

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #490 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. 
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #491 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]
« Last Edit: May 10, 2016, 02:10:47 pm by John Roberts {JR} »
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Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #492 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).
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #493 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
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #494 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
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #495 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 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. 
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Tom Roche

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Re: brain storm an optimal human safety system for back line
« Reply #496 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 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.
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Jordan Wolf

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Re: brain storm an optimal human safety system for back line
« Reply #497 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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #498 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
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Scott Helmke

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Re: brain storm an optimal human safety system for back line
« Reply #499 on: May 24, 2016, 09:58:42 am »

I, too, am eager to buy one.

Me too.
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Re: brain storm an optimal human safety system for back line
« Reply #499 on: May 24, 2016, 09:58:42 am »


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