"NSM" wrote in message news:fXZbe.8214$HR1.2086@clgrps12...

"James Sweet" wrote in message
news:6fYbe.12995$Nc.6863@trnddc09...

Paint half the shaft black and epoxy a reflective opto sensor or an IR
LED
and photodiode next to each other on top of the motor so you get a pulse
every time the shaft goes around.

Or epoxy a small magnet and use a hall sensor.
--


That would work too, though I would be concerned the magnet would fly off or
cause vibration. It is less sensitive to dirt though. A metal gear or other
toothed object on the shaft (cooling fan in the motor?) and a reluctance
pickup might work too.