Tachometers measure the speed of a revolving object. This is a pretty simple design with IR
http://www.instructables.com/id/Ho-to-Make-Arduino-Based-Digital-Tachometer-Simple/?ALLSTEPS
Tachometers measure the speed of a revolving object. This is a pretty simple design with IR
http://www.instructables.com/id/Ho-to-Make-Arduino-Based-Digital-Tachometer-Simple/?ALLSTEPS