In this quick Arduino tutorial I will explain how you can control a relay using the Arduino Board, one 1K and one 10K resistors, 1 BC547 transistor, one 6V or 12V relay, one 1N4007 diode and a 12V fan ...

Planning another Arduino build? If you’re just doing something simple like switching a relay or powering a LED, you might want to think about the Digispark. It’s a very small ATtiny-bas… ...

It has 250V / 5A Relays Outputs, 2A Digital Outputs, and Digital/Analog inputs and outputs, just like a regular Arduino, but everything is amped up.