I'd like to have direction sensing as well -- this is for an audio synthesis application, and the direction will be utilized as an additional control parameter. I've ordered a detentless rotary encoder to experiment with, but if you have further suggestions or ideas they are most welcome!

Whoops, obvious typo! You're right, I meant to say brushed! Thanks.

Well, it is to be used as part of a hand-operated crank -- imagine, for instance, something like a hurdy gurdy's wheel.

Thanks very much for the helpful replies.

The motors I've experimented with are common brushed DC motors. The potential divider suggestion works fairly well, although with the motors I have here the output range is fairly small.

I initially was drawn to the idea of using motors because of their feel while cranking -- they are smooth and have very little friction, resulting in continued motion after cranking and releasing, for instance.

However, perhaps a better idea would be to use as smooth as possible a detentless rotary encoder? Are there specifications addressing this which I could consult on a data sheet to find an appropriate model? Or are there specific suggestions for such an encoder? Thanks again.

I'm interested in using a DC motor as a sensor to measure hand-cranking speed. It seems like I could wire one lead of the motor to ground, wire the other lead to the sensor input with a resistor going to +5V. Is additional circuitry needed?

Also, this method only measures one direction of rotation. Are there suggested methods for sensing both directions of motor rotation?

(I also am using a rotary encoder as a sensor, but for reasons of touch and response I would like to have a separate motor sensor.)

Thank you very much.