Tracy and Mark.
This is the hot tip. Try it you will
love it. The 50 cent solution.

It works all the way from a few hundred
RPM up to 7500. CMOS chips like this one will tolerate
and clamp input voltages to 15 volts. Put a 15 volt
input zener on there if it makes you feel better :)

Take your pick. Up going or down going out put pulse.
This is one of my favorite chips. Almost
as ubiquitous as a 555.

I am done with this problem. I got my RPM counter
chips today so that is next.

Paul Lamar