Curious if anyone has abused 74AC series logic in a way I am suggesting.
Gauges in a lot of automobile instrument clusters use small stepper
motors with gear reduction. They are typically four wire types with
about 250 to 300 ohm windings. They'll work on 5 volts. 74AC logic is
rated for 24 mA so this could be an OK match. And I can drive two gauges
with one 74AC540. I know I can probably get away with driving directly
off a PIC or AVR but I intend to use the ADC and it's harder to get good
accuracy when driving heavy I/O loads.

I don't intend to tri-state the '540 so I don't have to worry about
latchup or add external diodes. I think 74AC is rated for a fair amount
of body diode current anyway.

So if anyone has experience doing bad things to 74AC logic, I'm all ears
:)

Too bad nobody makes a 74AC595. TPIC series is a little pricey.

Bob

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