January 3, 2010, 11:43 PM PST | Length: 344
Electrostatic discharge (ESD) is a threat when repairing computers. Bill Detwiler gives you a checklist for building a static-safe workspace. Once you’ve watched this TR Dojo video, you can find a link to the original TechRepublic article and print the tip from our TR Dojo Blog.
The most importand thing about ESD is not to achieve grounding, but: 1. To ensure that everything in your workspace (computer case, components, you and your tools) carry the same electric potential and 2. If there are any differences in electric potential, to discharge these SLOWLY over a resistance. So, it's important to notice that wrist straps and desktop mats are designed with internal resistance of several kOhms, to avoid sudden discharges. Good workarounds for temporary need: - Make sure that you and the computer are on the same potential by touching the computer case before touching any components inside the computer. (And make sure you continue to touch the computer case often, while you're working with it) - Touch the skin of your friend (shake hands!) just before you hand him an electronic device or component. For more permanent work spaces, it is very convenient (and safer) to bring everything towards ground potential, but for ESD, it is actually less important. Honestly, if someone is very concerned about ESD, but doesn't have the money to buy ready-made solutions, they should notice that the worst thing they could do would be to glue alufoil to their desk and connect it directly to ground potential, since any differences in electrical charge would immediatly lead to a sudden discharge when a component is put on the foil!
ive been working on hardware for years and i always get a different response from it pros when i ask about grounding or to avoid esd. in my confusion i just decided to keep myself connected to the case by touching it, so if i understand your statement correctly then ive been doing the right thing. thanks
ESD was not an issue, as CMOS technology was not yet in common use. As CMOS ICs became more and more common, we started receiving training on ESD mitigation. The RCA engineer who trained me in 1981 emphasized equalizing potential between components over achieving earth ground and pointed out that there may be cases where that is not only not possible, but undesirable. I have followed his instructions to equalize potential since then and have not had any obvious issues in almost 30 years of working with CMOS chips.
And I've worked that way ever since, no matter what equipment was involved. The problem is that very few people understand that "V1 = V2" Vg. "No difference in potential" is [u]not[/u] the same as "ground potential." The Shop Safety NCO inside me cringes every time somebody says "Leave it plugged in so it's grounded, then connect your wrist strap to the chassis."
I was encouraged by the video when personal safety was brought up. For the last 30 years I have been working on electronics, radar, satcomm and yes, cmos components in computers. I don't often wear a wrist strap or grounding device, it's unsafe around electricity. In tech school the Navy taught us the one hand rule on working on electrified components, you didn't want to create a new circuit path. Doesn't quite work when you attach a wire to your body to provide a path to ground. Touching the case and grounding yourself prior to working on something seems like a better plan.