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Author Topic: brain storm an optimal human safety system for back line  (Read 101910 times)

John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #380 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
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Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #381 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.
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Steve Swaffer

TJ (Tom) Cornish

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Re: brain storm an optimal human safety system for back line
« Reply #382 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.
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #383 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
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Tim McCulloch

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Re: brain storm an optimal human safety system for back line
« Reply #384 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...
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #385 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
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Mark Cadwallader

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Re: brain storm an optimal human safety system for back line
« Reply #386 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.
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Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #387 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!
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Tim McCulloch

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Re: brain storm an optimal human safety system for back line
« Reply #388 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?
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #389 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.
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Mike Sokol
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Re: brain storm an optimal human safety system for back line
« Reply #389 on: November 06, 2015, 08:49:40 pm »


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