The IR emitter/detector pair are mounted in a small moulded housing.
The emitter and detector are aligned so that the emitter beam is only seen by the detector when a reflective surface is in front of both of them.
hi,
Depending upon the motor shaft dimensions it is possible to fix more that one reflector to the shaft, say at 90deg points on the shaft, this would improve the resolution at lower shaft speeds.
Hi,
First try to understand what he is telling!. You will be getting a pulse of reflected beam for each rotation. This series of pulses you have to feed into the input of a counter circuit and and then output it to a seven segment display.
Yes, but I don't have a link.
The thing alternately powered the motor and then gauged back EMF due to the motor speed.
Depending on motor shaft inertia this was probably done at 20 Hz or 200 Hz or 1 Hz.