82c54 based computer "tachometer"

[sdbartho at cca.rockwell.com]

>Anyone want to start a discussion on automotive EMI and how much shielding is
>needed?
 
A few weeks ago, the local public access channel had a "learn-at-home" mechanics
course that was being broadcast from a couple of tech schools down south.

Anyway, they were working on the crank sensor on a 3.8 buick when they went into
a discussion on this very subject. Seems a lot of servicemen were forgetting
to put the shielding back on the crank/cam sense wires, and it was causing
random intermittent problems. The instructor then fired the car up without the
shielding, and showed the crank waveform on the scope. Full of spikes! The 
engine was also running like crap. Shield back on, everything was fine. A lot
of the problems had to do with proximity to the coil packs. 

You could probably get by with some creative routing, until you hit some outside
source of EMI. I can just see someone's ignition system going haywire in an 
airport parking lot. :)

Dig
sdbartho at hwking.cca.rockwell.com