This tutorial will guide you through the process of building a tachometer around an Arduino. Tachometers are used to measure rotation rate in Revolutions Per Minute (RPM). You don’t need much in ...

Here, the RC components (R5-C3-P1) set the astable frequency to drive the infrared light source (IRED1) through its driver BC547 (T1) — a general-purpose NPN transistor ... be sure to follow good ...