looking for GM smartcoil driver circuit...

[Orin Eman]

> | Anyone playing around with the GM smart coils?

> Grumpy was starting on a project with 'em.  Just toggled C from 5v to
> ground.
> NICE, spark.....
> Pain in the butt, plug wires thou.  If you find bulk terminals please share
> where, ya get em, please.
> Doc

I have been investigating these...

You have to raise the control line over 2.7V to 'arm' the coil.
It then fires when the control line falls below 2.5V _OR_
0.1 second later, whichever comes first.

So, toggling between 5V and ground works fine.  Input impedance is
high, over 10k, so you don't do any harm connecting directly to 5V.

I have driven them using an opto isolator (4N35), collector to
5V, emitter to resistor to coil, resistor to ground too.  I also
tried forming a darlington with the opto and a generic NPN in a
similar config.  Both methods work fine on the bench.

Other things that I noticed were that it takes approximately
25 uS between grounding the control line and the spark and
you don't get a very good spark with the control line high
for only 1mS.

As for connectors, I heard that wires that fit in some Bosch
distributor caps work.  I have yet to verify this though.

If I get chance, I'll check my driver circuits and post them
tomorrow.

Orin.