When I'm working on computers, I want to avoid eletrostatic discharge. I have a wristband, but I'm not sure that I'm attaching it to the right thing. Usually, I'll clip it to the case of the computer. However, there are two cases in which I'm not quite sure what the proper procedure is. First, sometimes laptops seem to have a all plastic case until you take them apart enough. Second, things like harddrives are ESD sensitive, but when you get them they aren't in any computer, so what should you attach to? That got me to wondering if it would work for it to be attached to a ground (like the third prong in a US outlet, which is attached to a grounding rod or water pipe). Could someone clear up for me what will work to avoid ESD and what will not?
Computer ground and wrist-strap clip should be connected.
As above. The aim is to get you and ALL the electronics that you are working on at the same "potential". This should ideally be ground potential - but it is more important that you and the work be at the dame voltage than that you be at ground. In fact, if you are at ground and the circuit you are working on is not, you MAY do more damage by having the earth strap than by not having it. May.
If there are two cases, ground or connect them both in some way.
They will often have a ground connection or a jack etc that has "grounded" metal. If none of these then see below.
You need an "ESD safe" work area. Typically this is a grounded work surface that is mildly conductive. An ideal material is "butyl rubber" which is used for roofing and waterproofing. This has carbon black included in it which is what makes it conductive.
A common metal sheet is better than nothing at all - just keep ALL power away from it.
ESD will discharge to ground quit quickly via a 1 megohm resistor. Connecting one og these in the wriststrap gound is wise - unless there is one there already.
You connect your wrist strap via a resistor to the earth pin of your wall outlet. The resistor value is typically in the 1M\$\Omega\$ range. Be sure to also use an antistatic mat, also connected via a resistor to earth to be sure everything you work is safe.