Arduino already include on-chip PWM controllers, making this effectuation easy. In short, PWM is a way of digitally encoding analog signal levels. MyDuino! Looking for a solution to build this circuit ...

The circuit on the left can interface with any one of those, plus any 5V logic signal if a dc voltage of 5, 12 or 24V is also available. 16mA has been chosen for the led current to match the drive ...