A tachometer is a useful tool for counting the RPM (rotations per minute) of a wheel or basically anything that spins. Actually ,this tutorial build a single input ,single output system. But this systems are useful not just for tachometer readings but also for reaction based systems. This project uses an Infrared beam to measure fan speed ,a character LCD to output the reading.
Hope you enjoyed reading this article and learned something about build your own tachometer with an Arduino! Source Arduino Tachometer