Question: Before we leap into this column with gusto and wild abandon, I have a poser for you to ponder. Suppose you are working on hobby electronics projects on your kitchen table and you've invested in an ESD (electrostatic discharge) wristband as shown below. To what should you attach the crocodile (alligator) clip on the end of the strap to give you a good ground connection? Now, read on...
When I was younger, I was a paragon of virtue with regard to taking preventative measures against ESD (electrostatic discharge). However, I'm ashamed to say that -- over time -- I grew a little blasé about this phenomena. Well, that was until quite recently when things like LEDs and MCU input/output (I/O) pins started to shrug off this mortal coil, helped on their way with an electrostatic "zap" provided courtesy of yours truly (it's just another service I offer).
Now the pendulum has swung and -- as is the way with these things -- I've become something of an ESD zealot. It started with my purchasing a humble ESD wristband similar to the one shown above. (Amazingly enough, you can get these from Best Buy; even more amazing, the folks at Radio Shack donít know what you're talking about when you say "electrostatic discharge.")
More recently, while rooting around looking for a toolkit to accompany me on my travels (see: What's the Best Traveling Toolkit? ), I invested in a rather nice 24" x 48" anti-static mat from those little scamps at iFixit. (This mat is intended for home use, of course -- I donít plan on carting it around the world with me.)
Based on this, you might assume that all is now well in the Land of Max (where the colors are brighter, the butterflies are bigger, the birds sing sweeter, and the beer is plentiful and cold), but there is one small fly in the soup, as it were. The thing that has been bugging me is the best mechanism to ground my ESD wristband and mat.
The folks in the next bay in the building housing my office have an easy time of this. They have fully grounded anti-static mats at each work area. Also, their ESD wristbands have banana plugs on the end and there are grounding points located in front of each work area as illustrated below.
Obviously, I donít have these grounding points mounted on my kitchen table at home, and I'm reasonably confident that the radiance of my wife's (Gina the Gorgeous) smile would no longer fall upon me if I were to install such an item. I have tried clipping the crocodile clips to the metal enclosure of my project's power supply, but sometimes I unplug this from the wall while I'm "tweaking" something, in which case I'm SOL (sadly out of luck).
Another approach I've tried is to have one end of a flying lead plugged into the ground strip on my breadboard, and to then attach the crocodile clip on my ESD wristband to the other end of this lead. We can see an example of this in the image below, which is from my blog on constructing my MSGEQ7-Based DIY Audio Spectrum Analyzer.
Observe the green wire that is plugged into the bottom right-hand corner of the breadboard and that exits from the lower right-hand side of this image. While I was working on this project, my crocodile clip was connected to the flying end of this wire (this is not shown in this image). There are several problems with this approach, not the least that it's easy to tug the lead out of the breadboard. Also, for this to really work, it assumes that the breadboard is actually connected to a ground point via a power supply or some other mechanism.
Another alternative would be to replace the crocodile clips with banana plugs, to splay these out a little at the end, and to plug them into the ground pins of wall-mounted power sockets. On the one hand this should ensure a good ground connection (we'd have to check the socket in question first -- experience has shown me that you can't rely on anything); on the other hand, it means that the cable on the ESD wristband would be stretched out to its fullest extent, which somewhat limits one's movements. Also, you'd constantly be bending down to plug yourself in or unplug yourself again.
And then, just this morning as I was mulling things over while driving into work, I had a simple yet (I think) brilliant idea...
To Page 2 >