What I have now is pretty much what you suggest, Mee_n_Mac. One problem I foresee with it is that someone cuts power to the device while the motor is running, and the motor runs past a count with inertia but the processor doesn’t register it because power has just been cut. Also, compared to what I have now, a pot would also be much more electrically simple - right now I have a voltage regulator to keep the sensor dc level constant over different supply voltages, because it is reflective, and detects a flat on the motor shaft. Are you thinking of a beam-break optical sensor?