I have built a simple test rig consisting of a variable power supply (DC); one 18 Volt DC motor; one disc with 60 'holes' which is connected on a shaft to the motor; and an opto interruptor switch. The slotted disc breaks the light beam as it spins through the the slotted switch.
I have powered the motor with 12 Volts DC and my multi meter set on Hertz shows 1.85 KHz. Remember the disc has 60 slots. Does this mean the RPM is 1,850 or have I got my maths wrong?
The next question is:- what changes if I replace the slotted disc (60 holes) and replace it with one that has 50 holes? The voltage supplied to the motor remains unchanged at 12 Volts DC. What is the RPM in this scenario?
Confused!
David HK