I work at my desk on prototype electronic devices. To the left of my keyboard is an antistatic mat that usually contains embedded prototypes and other electronic devices. The antistatic mat protects those devices from static discharge when I touch the mat before handling the device. Sometimes, though, I will handle the device right at my desk while I’m doing embedded design work.
I don’t like to be tethered by an antistatic wrist strap. I would much rather put a big old mat over the surface of my desk. The trouble is – antistatic mats make poor desk surfaces.
So I decided that the best solution would be a static discharge strip right on the front edge of my desk surface. I couldn’t find anyone that made such a beast, so I made my own. And I did it for about two dollars.
Below is a picture of the front edge of my desk without a strip:
My desk surface is made from a six foot long counter top from a home center. It has a smooth writing surface.
The strip is made from a disposable wrist strap from Digikey that is about $1.50:
The antistatic wrist strap is meant to be used once and tossed. It has static conductive material running the length of the strip that is wrapped around your wrist and then the other end is attached to a grounded metallic surface.
If you unwrap the strap, the leading edge has the conductive strip of material that should be put in contact with your wrist skin. On either side of the conductive strip is adhesive material much like athletic tape. The strip continues “bare” for a little it – long enough to wrap around your wrist. Then the conductive strip is covered by the adhesive material forming the “cord” just like the cord of a regular wrist strap. At the far end of the strap is a bare and sticky sheet of copper to adhere to a grounded surface.
To use the strip, I want to get rid of the adhesive tape material. The strip pulls away easily:
But when you get partway down the length of this disposable wrist strap, the conductive material is cut in a zig-zag pattern. No doubt this is to make the strip longer electrically to increase resistance:
There is just no way to make use of this section of the strip. It just stretches out like the photo below:
Luckily this section is only near the wrist end of the disposable wrist strap. I just cut the strip off at this point and I only lose a bit over a foot of conductive material.
The adhesive tape is removed all the way to the end where the sticky copper connects to the conductive strip:
Once the adhesive tape is removed from the strip, there is nothing sticky about the strip. So on the edge of my desk I ran a length of double-sided cellophane tape. The double-sided tape is a little wider than the conductive strip:
The copper end of the strip is wrapped around the bare end of a wire that leads from the side of my desk to a ground point:
The strip is then run from one end of my desk about 30 inches to the middle. This puts the strip directly in front of me while I work. Since the double-sided tape is slightly wider than the conductive strip, I used an Exacto blade to cut off the excess tape:
The strip sets in front of my keyboard – a place that I touch frequently with my arms:
This has saved my bacon more than once. I know that shifting around in my chair I can conjure up a significant static charge. With the strip there I am constantly at ground potential.
Many years ago my mom “grounded me for life”. I’m just fulfilling that command. 😛
Please post any questions you may have.
LifeHacker (http://www.lifehacker.com) just pointed to this article. I appreciate the attention – I read Lifehacker every day. I want to clear up their text, though. “He had an antistatic mat, but it was on the small side, and expanding it to the size of his work surface was out of the question due to cost and space needs.” I’m not sure how that conclusion was drawn. I have mats to the side of my desk and I didn’t want the mat surface for my desk. Antistatic mats are a poor writing surface. And, Ladies, there is nothing small about my mat size. Wink. *cough* *snort*
On a serious note is the concern about resistance to ground. If you work on live circuits, you do NOT want to be well grounded. I wrote “The copper end of the strip is wrapped around the bare end of a wire that leads from the side of my desk to a ground point.” and in my setup my ground point is my static mat connection. If you implement this desk strip, you should consider adding a series 1 mega ohm resistor in the line (the wire) if you connect directly to an earth ground connection. Play it save – do NOT ground yourself when working with any circuit that is live.