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Car Mechanics Discover ESD

The following article appeared in the Spartanburg Business Report June 2000

Jon Woods and Gary Nugent, Certified Master Mechanics, wrote the following dissertation for Copley News Service.

"Remember the TV ads that showed your socks stuck to the wife's dress? Or how about the latest one, the little boy that finds if he shuffles his feet on the rug he can nail dad with a big jolt! The point is that a little dry heat, some friction (tumbling clothes or shuffling feet), the right fabrics and "zap!" you've got yourself "ESD." (Kind of sounds like a social disease.) ESD stands for electrostatic discharge.

What does this have to do with cars? Since 1980, manufacturers have been adding more and more electronic gadgets. Most recently we've seen navigational systems, high tech-stereos and even satellite communications (Cadillac's "On Star"). All of these electronic goodies contain semi-conductors like transistors and diodes. These components are extremely sensitive to voltage surges, especially "ESD."

Now do you see where I'm going? Believe it or not, you can generated as much as 25,000 volts just by shuffling you feet across the carpet under the right conditions. This is a significant problem for the technician servicing your car. You see, it only takes about 50 volts to destroy a transistor in one of those "black boxes." All your mechanic has to do is slide across the front seat and then carelessly touch the wrong connector and "ZZZAAAPPP!"

The new-car manufacturers recommend the use of a wrist "grounding strap" (a long wire attached at one end to the car body the other end to your wrist with Velcro). This serves the same purpose as the rubber strap that drags on the ground under those big gas trucks. Now I hate to admit it-- but not many technicians use them. However, the good techs are cognizant of the possible damage, so they ground themselves by purposely touching their body to the car's sheet metal before they touch any ESD-sensitive electronic component.

ESD is not normally much of a problem for the typical car owner-- unless-- the owner is a do-it-yourselfer. If YOU fall into this category, please heed this warning "ESD KILLS"-- computers that is. Remember, just sliding across the car's seat can generate enough electricity to change your VISA balance significantly!

Huh! I wonder if a sheet or two of Downy or Bounce in the trunk will cure the problem?"


The ESD Journal recently received this insight from Dirk Kubernus a Quality and Reliability Engineer. We thought readers would appreciate his comments:

OnStar was originally designed by Hughes Networks. I was the lucky guy who got to run the Qualification Testing. The base unit had a demodulation IC that is rated at 150 volts ESD threshold! It did not take much to blow the output of this device even once soldered to the PC Board. This entire story I will one day write up and present at the symposium. But what I wanted to add here is that mechanics need to very aware of what ESD is now days. At 150 volts it does not take much to blow the output even within the enclosure.


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