Monday, January 19, 2009

General guidelines for high voltage area?

What is general guide lines for EPA area, where live AC and DC equipment is used?

If personnel are handling ESD sensitive devices, the general guidelines are the same as for any other ESD Protected Area. See my ESD Guide.

However where high voltages are present there may be a safety concern about earthing the body either through a wrist strap or through conductive footwear and flooring. In this case the risks must be evaluated and if necessary, the ESD precautions modified to reduce safety risks to an acceptable level.

Usually, wrist straps and footwear for ESD use have a minimum of 750k ohm resistance, which is designed to give some protction for up to 250Vac systems. For higher voltages higher resistance (pro rata) can be used if desired. If the risk of shock is unnacceptabe it may be necessary to avoid grounding personnel and use other ESD protection methods. There is no general advice on this as far as I am aware.

ESD damage to motherboard?

I have a computer motherboard and I plugged it in a week ago and plugged it back in 2 days ago and now I got power but no video, no keyboard/ mouse, or hard drive activity and I'm told it is do to static build up how do I get rid of it?

If you have already damaged a board through electrostatic discharge (ESD) the damage can be permanent. This is why it is important to prevent static building up on your body while you are hndling the components in the first place.

The usual method is to wear an ESD wrist strap. When replacing a board, disconnect the computer from the mains and connect your wrist strap cord to the computer chassis. Don't take the board out of its packaging until you are ready to plug it in, and don't place it on any ordinary surface. Whilst attached to the computer via the wrist band, take the board out of its packaging and plug it in. Do not touch any of the ESD sensitive parts of the computer unless you are "grounded" to it via the wrist strap.