motor spinning condition

I have a brush on a motor for which I must be sure that is spinning. Any recommendation for a sensor that will output only condition.
Or any other recommendation how to solve that issue.20210621_131706_compress96.jpg
Hi Orkorginor,

You could attach a reflector onto the metal brush housing, and use a photoelectric proximity detector... so when the brush is moving the beam will reflect each time the reflector passes the sensor.