Hello everyone! I hope you are doing well. In this tutorial, we will study the relay from its basic construction to practical selection and control. A relay allows one electrical circuit to operate contacts in another circuit. This makes it useful when a low-power controller must switch a different voltage, a larger load or an electrically isolated circuit. We will focus first on the common electromechanical relay because its moving contacts make the operating principle easy to understand. We will then compare electromagnetic, reed, solid-state, thermal and hybrid relays, calculate coil current, discuss contact ratings and examine a safe microcontroller driver. A relay is often described as an automatic switch, but that short definition hides several important details. The coil and contact ...