Author uses audacity, tape, and uses that to figure out the speed of the motor. Oh you need a mic too
http://www.instructables.com/id/How-to-Measure-RPM-of-Motor/
Author uses audacity, tape, and uses that to figure out the speed of the motor. Oh you need a mic too
http://www.instructables.com/id/How-to-Measure-RPM-of-Motor/