Motor Speed Meter

[fabbie]

Hey i was wondering if i could do this. using the back-emf of a motor to measure the rpm. Is this possible?
Or are there other methods to do this?

 

[bmcculla]

It's possible but a bit complicated. It's much easier to use another small motor as a generator.

 

[fabbie]

How about using infrared sensors to count the rpm?

 

[bmcculla]

You can use a LED and a Photo diode to make an opto-interrupter. You can also buy them in one package designed for this purpose.