this capstan motor I pulled out of a 1970s era VCR has three hall sensors. on close inspection, the hall sensors are just a tiny pair of coils stuck into the stator and shielded off from the main drive stator cog poles. so when the rotor spins, a few pissamps of AC gets generated and comes out either side of these coils with their own outputs.
this signal goes into an amplifier to turn it into logic signals indicating the speed of the motor. Possibly direction as well. I haven't got that far into destruction yet.
