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http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29

I'd be worried if you get a shock of that magnitude (able to affect muscles). Perhaps there's a fault? Perhaps the metal desk needs to be earthed?

Pew446: ..., and maybe provide some tips on preventing it in the future.

be thankful it was not high voltage. Use a wooden desk.

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Voltage hurts, current kills.

Ground is a relative term. Earth ground is 0V, the ground on your project might have a floating ground of 1V. Most likely it was because your project was insulated that you where able to make a circuit threw your body.

But as I said current kills, that sensation of it forcefully contracting the muscles in your hand, think about what happens if that happens on your heart. It only takes 75mA to kill, so never intentionally do that.

Voltage hurts, current kills.

Ground is a relative term. Earth ground is 0V, the ground on your project might have a floating ground of 1V. Most likely it was because your project was insulated that you where able to make a circuit threw your body.

But as I said current kills, that sensation of it forcefully contracting the muscles in your hand, think about what happens if that happens on your heart. It only takes 75mA to kill, so never intentionally do that.

A 4'x8' sheet of laminate (like on a countertop) is about $50. Much more durable than acrylic both in scratch and heat resistance. Your local "big box" store will have it, although they usually only keep white or ugly granite styles in stock.

i would say don't try it again and try to use a wooden desk.

Honestly, put a voltmeter between those two points and measure AC and DC potentials. If you get about 1/2 the line voltage, I have a possible explanation.

I had an issue like that where two PHD's spent a weeked together trying to figure out a spark between to "grounds". When I came in on Monday, I had their problem identified in about 5 minutes.

Then there was a story I heard about where one side of a lab had neutral attached to the wrong terminal. It's easy to do because of the color code. I was in an Explorer's post at HP many years ago and the "instructor" told us how to hook up the line cord with black, white and green. I informed him, he had it wrong.

majenko: http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29

Not to be confused with an aeronautical ground loop in a taildragger...

Pew446: Thanks for the replies! I don't have a wooden desk, would it be enough to cover the desk in plexiglass?

No!

You don't want anything that can build up a charge of static electricity when working with electronics.

Hi, have you had the supply that you were using for 5V checked, as in insulation to earth, ie earth leakage, also isolation of the 5Vdc from the mains input?

Everybody is trying to tell you how to avoid it, If it was me I'd be trying to find what caused it, in case it is a failing component that my cause deadly results when it finally fails for good.

Tom...... :) ps I'm not sure where you are from, if USA the you will probably not have an earth pin for the power supply.

Pew446: I was working with 5 volts at a max of 1 amp while working on the project (though I don't know the exact current usage.)

The wires coming out of the 5V power supply should be "floating".

ie. There's 5V difference between them but neither is referenced to anything else in the universe.

It sounds like that isn't the case.

One way to find out would be to connect them (one at a time) to physical ground through a resistor and measure the current flow. It should be zero (no current flowing from the PSU outputs to mains ground)

If you're feeling gung-ho, just touch the output GND wire to the ingoing earth wire (assuming there is one), see if it trips the circuit breakers. If everything is correct then nothing should happen. (waits for people to scream at me....)

fungus:
(waits for people to scream at me…)

Before you hate on me, I just tried it on my (correctly wired) 5V power supply.

(put your money where your mouth is, I say).

It was fine…nothing happened. Apparently my 5V supply is correctly isolated. :slight_smile:

Check your power supply! That isn't 5V you are feeling, unless your hands were just soaking in salt water.

It sounds like an issue with 120V AC leakage. Perhaps there is a problem in your power source, or it is a badly designed power supply. Or maybe some other piece of electrical equipment has a fault that is energizing the desk. Or there may be a fault in the wiring going to your outlets.

Connect a 22k resistor between your ground and the ground on your incoming AC power. Measure the AC voltage across it. It should be under 1Vac.

Now make the same measurement with the resistor connected between the desk and some other good ground like a metal water pipe. Something that actually goes into the ground.

Then make the same measurement between the ground on your AC outlet and the water pipe ground.

All those readings should be under 1Vac. If there is voltage between AC ground and the water pipe ground, call an electrician. If that is OK, but there is voltage on the desk, start disconnecting things on the desk until the voltage disappears.