I'm interested in building a PIC based logging tachometer for evaluating some small DC motors. The PICMicro Motor Control Tips publication ... mentions measuring the back EMF voltage from the motor while the PWM signal driving the motor is off and using the voltage to measure RPM or a given drive voltage. Has anyone used this type of technique and developed a more detailed project description somewhere? I'd be interested in other techniques to explore as well. Tim -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist