60V DC dangerous?

Good enough reasons for me.

One problem with this measurement is getting a steady reading when you're holding the leads in your hands. Maybe you're better at a more consistent grip than I, but I seem to recall when I've connected myself to an ohmmeter in this way the readings drift around a lot as my grip relaxes / becomes firmer.

Then there's the whole sweaty-vs-dry skin inconsistency thing. Do you feel you're able to do this repeatably? I guess one could get whatever conductive oil or gel they use for taking an EKG.

Mark

In article , John Larkin wrote: [... me ...]

In the brain chemicals and electrical pulses are all there really is. A memory is just a bunch of chemicals arranged in a certain way.

There may be something about the problem memory that makes it more likely to be deleted. The brain also tends to spread memories around. This makes it hard to notice the memory loss in someone like a stroke victim. Often the whole subject isn't gone. Just some of the details get fuzzy. The brain tends to fill back in the details.

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kensmith@rahul.net   forging knowledge

Naaa, thats only when the cameras are on. Otherwise it is "Here bite down on this while I plug in the lamp cord".

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kensmith@rahul.net   forging knowledge

Anaesthetic.

Cheers! Rich

A DC must be trated much more respectfull than AC. There is no zero crossing and you can't pull out once it get you. Dangerous currents are starting from 1...5mA, depends by the skin resistance which coud be any and the path on which current is flowing through the body. Any path considering the hart is dangerous.

greetings, Vasile

Sounds like any other serious medical procedure, just a lot less blood involved.

John

People don't usually walk around with conductive gel all over their hands. I wanted to see how much DC would cause a shock under normal lab conditions.

Any experiment yields better data than no experiment.

John

"The experiment was a success - upon reaching a current of 45 mA, the scientist went into ventricular fibrillation. Time of death was 10:12 AM,

8 July, 2006."

;-)

Cheers! Rich

It's interesting how many people, especially electrical engineers, are afraid of being shocked. I like to feel parts on a board to see what's getting hot, but I know guys who won't even touch a board with +-15 opamp supplies, and one guy who won't touch a pure-logic board, +5 volts. But then, I know grown men who are afraid of needles, snakes, spiders, women, or frogs.

I've been doing a lot of AC wiring in our "new" building lately, and I usually do it hot. 120 AC isn't a big deal if you do happen to touch it. You can hand-twist the hot conductors before scrunching on the wire nuts, with just a bit of forethought. It's like ESD: if you handle things right, you don't need a lot of special gear.

I'd imagine that hot-wiring 230 volts would be a little more interesting.

John

On Fri, 07 Jul 2006 09:52:28 -0700, John Larkin Gave us:

I too can get drunk on a mere few beers (like 6).

I rarely do, however. Typically, I drink a single beer as a beverage at night, when I return home from work, while watching the news.

Best beer in the world: Chimay Gold Belgian Ale. Made by trappist monks in a monastery, and it tastes like it has been blessed.

$12.00 for a 26 ounce bottle.

On Sat, 08 Jul 2006 00:19:35 GMT, "Rich Grise, Plainclothes Hippie" Gave us:

Fucking retards that drink to calm themselves need to see a doctor and get Chlorpromazine for the job. Then... take ten.

See you on the other side.

On 7 Jul 2006 18:31:56 -0700, "vasile" Gave us:

Zero crossing is meaningless. It WILL allow an arc to quench, but no human in the world is fast enough to pull away during zero crossing as it happen 60 times in one second, and your nerve impulses don't even travel fast enough.

You are spreading misinformation.

Rum and coke is a simultaneous upper/downer!

John

230V is much more interesting if you reach over and touch the scope with the other hand!

On domestic power here in North America, it's just as interesting, or not. 120VAC to ground. Fault currents on 240V industrial circuits can be high enough to cause injury from molten or vaporized metal if you accidentall short it though. Usually shorting a 120V domestic circuit isn't very exciting.

600VAC 3-phase industrial power, OTOH (a mere 480V in the US), OTOH, is a *lot* more exciting.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

In the UK most small businesses/light industry makes do with 415V 3-PH, I think there was once an earlier standard of 380V.

Our place, like most small businesses, is wired 240 line-to-line three phase...

c

a n b

where a-n is 120, b-n is 120, a-b is 240, and a-c is 240. The "high leg", line c, is called the "stinger" phase. n is nominally ground.

Residences usually have just the a n b part.

John

In article , Roy L. Fuchs wrote: [...]

Make that 120 times per second.

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kensmith@rahul.net   forging knowledge

On Sat, 08 Jul 2006 11:14:14 -0700, John Larkin Gave us:

I usually do shut down if no other devices are affected, but i have done several kitchen jobs with the breakers on because I didn't want to have the refrigerator loose (gain) thermal energy.

The trick is to be smart enough to a: never touch it, and be make touching it a non issue, should it happen. If you are "floating" there will be no shock. There may be a very small influx of electrons to charge you up like a very small capacitor, since you are above ground potential, but that's it. Also, that would have to happen right at the peak of the cycle, and gets nullified 1/120 th of a second later.

Yes... well America is known for accommodating ALL user types when setting a standard or educating someone. So they teach no live circuits and a hand in a pocket. etc. You and I can work hot, but not all folks that get into this industry has that much "presence of mind".

Even we can make a mistake. Sometimes, you only get to make one.

Regardless of what one teaches, one should always teach that as well. The best philosophy is that one only gets to make one mistake. This reinforces the risk in one's mind, even if the level is false, it is safer.

Keeping one's self "balanced" to ground potential works. If you are standing still. Walking across a room with an fpga chip in hand whether pins up or pins down is dangerous for the chip.

Ever heard of "infant mortality"?

I wouldn't want to build something or repair something that is designed to keep men alive, or to save lives knowing that one event (which you cannot see) might lead to an early failure in the field at a critical moment. If all that worked in the industry took the correct steps to ensure that no such event occurs, we would all have products that last for a very very long time. An ESD event doesn't have to cause an immediate failure mode to cause damage and be the root cause of a future failure..

I will not work at those levels hot. Even I know enough not to play with matches at a gas station.

I would create and test products that make much higher voltages, and then operate them live, but there are several procedures in place for such bench operations. We did DC to DC converters for outputs from

250 x 2 (plus and minus) to 400kV units over in europe for transmitters (the most we did here was 180kV X-Ray supply for an airport scanner. The tube alone was $900 each, made by some famous German doctor/xray tube maker)

Anyway, HV stuff like that gets fired up inside cages with no persons inside at the time. All setups for loading and metrics have to be in place. The most we have run in an open lab or on an open bench is

50kV. I worked with 15kV to 40kV practically daily for years... not anymore though. Now I convert HV into little tiny powerful waves...