I have a circuit which measure rpm of a centrifugal mixer, it uses a hall effect sensor to measure rpm, but unfortunately, this sensor fall down quickly and it is very expensive, the circuit uses micro controller AT89C2051. Is there any idea that I can replace the hall effect sensor by other sensors like infrared or any other idea ...
if you are still trouble in hall effect sensor try tachometer speed measuring idea.
if you are interested to control speed from measured data, go through following link