A basic circuit to make LEDs fade in and out by switching power on and off.
The speed of fading in and out can be adjusted by changing the values of the capacitor and/or the resistor in the middle.
By switching on, the capacitor is slowly charged through the resistor. The more 'juice' the capacitor loads, the further the NPN bipolar transistor opens up to let current pass towards the LEDs, making them fade in.
If the switch is turned off, the capacitor empties itself through the LEDs, making them fade out again.
The circuit is designed to handle 14.2V, so it's suitable for automotive use.
