Tingle from homemade projectors

[neutrino]

Hi guys,

I've been meaning to ask this for a while but other things kept cropping up.

I have 4 home built projectors. 2 blue satallites, 1 GB (waiting for red) main projector, and a smaller RGB.
I have followed Bill's wiring document (correctly, I think!) but if I touch some bare metal ie not painted sometimes I get a little tingle which is pain in the butt when I need to align some of the mirrors/dichros.
I am on a small island atthe moment and the power is supplied by a diesel generator. I have just measured the voltage with my meter and get the following readings:

Live - Neutral 128.2V
Live - Earth 11.5V
Neutral - Earth 8.0V

Any ideas what is causing this? Is there any way to over come it? It isn't too much of a problem with the blues as there is nothing to align. GThey are also but inside a fireproof fibreglass case (electrical junction box).

Any help or suggestions would be appreciated.

Cheers
Rich

[Stoney3K]

Is the diesel generator properly grounded (earth pin driven into the ground)? If not, it's possible that it's carrying a leakage current and that's causing your tingles.

The N-E voltage should be zero. If not, your earth circuit is messed up outside the projector.

[neutrino]

good question. I have no idea. The power is run by a private company although a small island it still feeding 3-4000 people. I am based in the Bay Islands of Honduras.

Im pretty sure the whole island is pretty messed up for power hence the N-E and L-E voltage. Is there anyway to prevent the leakage current?

Cheers
Rich

[logsquared]

Check to make sure the AC power supply is properly grounded at the point it enters your building. Sounds like you ground is floating. Live to Earth should be ~120volts or so. If there is no way to ground the incoming power supply maybe consider a isolation transformer.

[neutrino]

I will have to check with the building owner about the grounding and where it enters the building. Does the isolation transformer need installing or is it a module I can plug inline with the mains supply to the projectors, maybe one for each projector? or one for all projectors?

Cheers
Rich

[massivesound]

If you're measuring 11V L-G and 9V N-G, that means your source is not grounded at all. Use a 3 wire power cable, and connect the green conductor at some point to a ground rod. If your building is wired with 3 conductor cable, the ground conductor just needs to be grounded at the electrical panel. The enclosure of the projector and all of the exposed metal parts inside should be connected to this ground conductor to bring it to zero volts to prevent the shock. If it's a 2-wire system, you can physically connect the projector enclosure to a ground with a separate wire, or get a small 1:1 (120V to 120V) isolation transformer. That will still make your projector "float" (be ungrounded) but when you touch it you'll bring it to ground potential through your body and won't feel a constant shock.

[-bart-]

NEVER, EVER GO EARTHING ANYTHING TO PLUMPING OR WATERPIPES YOURSELF !
You might know what you're doing, but lots of morrons lurking forums worldwide don't.
If you feel something is out of order, contact a qualified electrician.

Live - Neutral 128.2V
Live - Earth 11.5V
Neutral - Earth 8.0V

Are you measuring this at the walloutlet, or somewhere at the end of an extension cord ?

You might want to check other walloutlets in your house, maybe its down to one particular piece.

[massivesound]

Point taken and reference removed. Drive a ground rod and ground your chassis to it. That could happen through a ground conductor in your building's wiring system if present, or through a separate conductor.

[steve-o]

How many miles away is that generator? Ground potentials can change. Do you have experience with high voltage electrical wiring? It can be fatal if you don't know exactly what you are doing.

[neutrino]

A qualified electrician out here could be asking too much!!! Everyone thinks they know everything.

I took my motorbike to a mechanic to be repaired and have a new shock installed. I even provided the Clymer manual and they still managed to put it in back to front! Muppets.
I just wish I knew a bit more.

NEVER, EVER GO EARTHING ANYTHING TO PLUMPING OR WATERPIPES YOURSELF !
You might know what you're doing, but lots of morrons lurking forums worldwide don't.
If you feel something is out of order, contact a qualified electrician.




Are you measuring this at the walloutlet, or somewhere at the end of an extension cord ?

You might want to check other walloutlets in your house, maybe its down to one particular piece.