new tach circuit

[Rick Sparber]

Although I got my tach to work, I've never liked how it's values must be
tweaked to make it work. I've been working on a circuit that uses feedback
to automatically center the IR source in the center of the receiver's range.
Such a circuit is very easy to design given lots of parts. The challenge for
me is to do it with as few parts as possible. The old tach circuit uses 2
resistors, the IR source, and photo receiver. I have a circuit that uses and
additional resistor and a capacitor. Haven't built it yet but I doubt I
could make it any simpler. I also have my doubts about how well it works.
The next step up uses 2 more resistors, a cap, and a transistor. I have a
bit more hope for it. Stay tuned...

Rick