Fritzing Creator Kit - #08 Amplification
Basically, the Arduino board is a control unit. It supplies each channel with a current of 40 mA. This is sufficient for smaller loads such as LEDs. For larger loads (such as motors, solenoids or valves), an additional electronic switch is required to conduct larger currents.
The example shows a circuit with a separate power supply. GND of the power source must be connected to GND of the Arduino. The code from the blink or fading examples can be used for this. The pin from the blink example must be changed to pin 9.