Back EMF and Brush Motors

Hello all

I was thinking of using backemf as a sensing scheme for my brushed dc motor. I know it can be done for a motor however motors have some tolerance in mechanical specs. So this technique might be good for a single motor but will it be feasable if i mass manufacture a device with a backemf control system using the same king of motor?

Any help on this matter will be greatfull

Thank you. depends. What are you trying to sense? Speed?

I don't think you're going to see that much variation from motor to motor. You can always try your scheme with 10 (or more) motors and do some statistical analysis.

Yes Sir! trying to sense rpm. Just want a sensorless machine... im using a hall sensor but would prefer not to have an external sensor and have rpm measured by back emf. Im just worried that it wont be consistant from motor to motor and as load changes

It is going to be pretty tricky. Back EMF is noisy and tough to pick out of the driving signal. It will vary with load.

Good luck!