Car Mechanics Discover
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
"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
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
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
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.