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 ...

The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, ... – 2A internal switch means you can get out 500mA from as low as 3V, and at least1000mA from inputs as high 12V ...