Sometimes you want your Arduino to control AC powered devices like lamps, fans or other household devices. But because the Arduino operates at 5 volts, it cannot directly control these higher voltage devices.
That’s where the relay module comes in. You can use a relay module to control the AC mains and Arduino to control the relay.
This tutorial walks you through how to setup the relay to switch on a lamp or other device, but let’s begin with a short introduction into relays.