High Voltage Ground

I'm starting to work with high voltages again, but for real this time. I just built an ignition coil driver, using a 555 (and I got an ignition coil), but my 555 broke (the texas instruments ones can only drive 15mA, oppose to the normal 200mA, oops) so I have to go buy one today. My main question is what to use for ground, whether it be for an old screwdriver for arcing sparks or the secondary of a tesla coil. I was originall just going to use the 3rd prong of an outlet, but somewhere on the internet I heard this could destroy all surge protected power strips and destroy all plugged in electronics at your house. I, of course, do not want this cause... well... I'd be screwed. Is this true or not? Can I use the 3rd prong?

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NachoMahma9 years ago
. I'd drive a metal rod/pipe at least six feet (two meters) into the ground and run a wire from there to the workbench.
guyfrom7up (author)  NachoMahma9 years ago
I was afraid of that....
. Unless you have a larger-than-very-low-current-output HV source, I can't imagine you overloading a proper house wiring ground. They can handle (some) lightning strikes. But why tempt Fate and Mr. Murphy? A lot of house grounds are not what they should be. :( If you don't have a very low resistance path to ground, HV can cause problems.
. The closer you are to the ground rod (should be one near your meter), the less effect you will have on other equipment (assuming your connection to the ground rod is good).
. I'd still go with a dedicated ground rod. It's not that big of a PITA and well worth the effort. Try to drive it at least 2-3 feet from the meter ground rod.
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. Or use a metal cold water pipe, preferably where it enters the house. Connect as close as possible to where it comes out of the ground.
guyfrom7up (author)  NachoMahma9 years ago
well, here's a delema (I totally butchered that spelling) I can't drive a pipe/rod that far into the ground cause of bedrock and where my basement is located The ground around me is pretty... well about half clay, not very conductive My mom doesn't want my connecting HV stuff to water pipes cause you know, water, high voltage what to do!
. Could you find someone your Mother would consider to be an authority to explain to her that using the water pipe is safe? . . BTW, it's dilemma.
guyfrom7up (author)  NachoMahma9 years ago
I'll ask my dad later, he'd proabably say yes :)
guyfrom7up (author)  guyfrom7up9 years ago
ALSO how do I know that it's a good ground?
. If it's a metal pipe that goes underground, it should be a good ground. . The equipment to test earth grounds is pretty expensive, even to rent. An ohmmeter will tell you if you have a bad ground - measure between the meter ground rod and your spot on the pipe. You can also measure the voltage between the pipe and your receptacles. If there is any voltage pipe-to-neutral or pipe-to-ground, you have a problem, possibly in the house wiring.
guyfrom7up (author)  NachoMahma9 years ago
ok, I found a copper pipe that I think is the closest to the ground as possible, it's near my water softener, and it goes into the wall out the house. Near the wall it's wrapped with black insulation and it goes into a PVC pipe...
...near my water softener...goes into a PVC pipe...

Are you on a well? Then the pipe is not ground, wells use plastic pipe. You have to be on city water, with metal pipe going to metal water mains for it to be a good usable ground for house wiring. And many newer homes have plastic somewhere between house and main.

Can't drive down a rod? Then bury a plate. Attach wire to a plate and bury it deep as possible where the ground will stay moist as it gets. Surface area is what counts. NEC would like for a house ground a copper alloy with 5 sq ft exposed, min 0.060" thick (1/16"), at least 30" down. For playing with HV, chunk of sheet metal, maybe only 2 sq ft. Got an old galvanized bucket? Attach wire nice and solid, bare wire is best, bury deep.

Follow the sound careful advice, stay away from the house grounding.
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