My Bot is Shocking Me

[daniel]

Hey Guys,
I just moved my bot into an older wood framed house. It is grounded just like it was in the concrete garage it was in before, with copper wire that goes from the machine to an electrical outlet. It only shocks me if my shoes are off. The floor and walls are made of wood, Which way is the static electricity flowing? From the bot to me or the other way around.

What is the best plan of action?
Thanks again!

[harryball]

Grounding the machine frame would be my suggestion. I would not connect it to the house ground, my preference and paranoia I guess. I would run a separate ground out to the house grounding rod or drive a new ground rod nearby and use that for my dustcollector ground too.

Robert

[patricktoomey]

I agree, I've seen too may houses with ground wires broken away from the grounding rod. I would do the separate ground rod to be sure and also check the houses grounding rod to be sure it's ok.

[daniel]

Thanks Guys, I'll have to try and locate this grounding rod, I don't know much about them and I hope its not up underneath this house. Where is the grounding rod located on most houses? Is it near the power meter usually? I would rather fix it than try to drill a hole to run the wire from my bot to it...

[patricktoomey]

It should generally be near the meter base. You will probably see a rather large, bare wire running down the wall and into the ground. You may or may not see the top of a rod sticking up where the wire will be clamped to it.

[waynec]

'Twere it me, I'd just bang a new ground rod into the ground, and run your ground to that.

YOu can get a cheap circuit tester that plugs into the house outlet that will tell you if you have a ground problem, or other wiring faults.

A local electric supplier should be able to provide a ground rod. I just used a fence post driver to drive it into the ground. It can even be angled into the ground if you don't have room to pound it straight down. The electric supplier can also provide the correct type of clamps, and the copper cable.

That new rod needs to be close to the existing one- within 5 feet if I recall. The existing one would normally be close to the homes service entry or fuse panel- within 20 feet for sure. Find the bare copper cable coming from the fuse box, and the ground rod will be at one end. In older homes, sometimes this was grounded to the plumbing. Not a good idea, and not current code (I think). If that's the case, I'd move the house ground to the new grounding rod.

If you do that, I'd be sure to turn off the power. While ground doesn't normally have any voltage, if there is any short or leaking electricity, when you disconnect the ground you'll get a nasty shock.

Its a pain to pound the rod in, but other than that its not too bad. YOu may find it fixes other things like computer problems or funky outlets as well.

Wayne from White Salmon

[paul_z]

Do you have a dust collector attached? If so, be sure to run a ground wire through the hose and to a good ground as well.

[dhunt]

About halfway down this thread...
http://www.talkshopbot.com/forum/messages/7/8527.html
it turns into quite a discussion re. grounding/earthing,
including the neccessity to deliberately select a damp/moist area
for your new ground-rod's position!

Go there.. read.
http://www.talkshopbot.com/forum/messages/7/8527.html

[danhamm]

Hmmm..says the "human capacitor" as he walks to and fro on his "nike's" his nylon strip carpet
charging his body to lethal potential,I wonder
what little epart I can destroy this time...
Sometimes...Daniel it has no bearing on your "grounding earthing" just your environment,
and your footwear and or matting or lack of..the mahine just becomes a discharge point...cheers

[trakwebster]

I've had good luck in the past -- grounding various electronic and telephone equipment, computers that must talk to each other, and recently my ShopBot -- by finding a cold-water pipe and grounding to that, because as you know, the cold-water pipe goes fairly directly to the earth.

I've always been in places where the pipes are metal. I don't know if there are any pipes which are not metal. If so the old cold-water pipe wouldn't work.

The hardware store has a clamp that bites into the pipe a little bit, and I generally use large wire, size #10 or so.

Earth grounding has a pleasant habit of eliminating various puzzling gremlins with electrical and electronic devices. I like it.

[mikejohn]

Daniel
Touch something else which is grounded, away from the 'bot, see if there is a static discharge.

..............Mike

[3d_danny]

Ground rods are notorious for being an unreliable ground. A ground rod is only effective as the materials(earth touching the rod) ability to conduct electricity.

If you look at the ground rod associated with the electric meter on your typical house, it is usually under the roof overhang, and if there are gutters, is a somewhat dry location. If the soils is damp, it doesn't necessarily mean the earth can conduct electricity, although it has a better chance of conductivity. It has to do with the chemical makeup of the soil. Some rods will only conduct after a certain voltage is reached and that can vary from time to time on the same rod.

I worked many years for a communications company in their transmission and testing department and we tested thousand of grounding installations with a wide variety of results. I have seen a single rod test perfectly and on the other hand, a ground field consisting of 20 interconnected rods, each 50 feet long, completely unusable.

The best available, low cost ground, going back to the electric meter, is not the meter ground rod itself, but the ground wire that exits the electrical meter to the rod. This wire is tied to the power company ground grid...a very good stable ground.

The reason for attaching directly to this wire and not the rod is that many ground rods are galvanized ( a better one is copper cladded ) and the there is a possibility that the clamp that is used to connect to the wire to the rod is either loose or doesn't conduct very well. I have seen many that clamps were knocked loose from the rod by lawnmowers, etc. If the clamp doesn't work, your have a questionable ground. Also, the power company doesn't really care if the rod will conduct low voltage/current, (static etc) the rod is there to only help dissipate a megavolt lighting hit.

If you attach to the power ground wire, be sure to use a quality clamp, such as a copper coated "Fargo" clamp. These can be made very tight and will not come loose.

A cold water pipe ground sometimes works, but there are conditions that may make it unreliable. There is the possibility of plastic/pvc pipe feeding the house from a the water meter, making it a questionable ground. Using the water in the pipe as a ground is not a good idea. Most cold water pipes in a house derive their ground from, again, the power ground using a clamp somewhere within the house. I have seen clamps on older copper pipes that are loose from the constant expansion and contraction of the pipe.

Dan

[daniel]

Thanks guys, I have found the grounding rod and the wire connecting it. From a visual inspection alone It looks shoddy and terrible at best. So my first course of action will be to get this fixed... I will then report back the results! Thanks again!

[olecrafty]

To aid in the installation of a new ground rod. A little water and working the new rod up and down is usually easier than a big hammer.

If you really need to get serious about grounding do a search for (chemical ground rods) and read on.

Kaiwa
olecrafty@charter.net (mailto:olecrafty@charter.net)