Powering the LED from Raspberry Pi GPIO
The Sangaboard v0.4 provides an output to drive an LED, this uses a Darlington pair driver to allow it to be switched. If a Sangaboard v0.4 is not available, you can also power the LED by wiring the LED-and-resistor assembly, or the illumination PCB, directly to ground and 5v on the Raspberry Pi GPIO pins. The correct pins to use are shown in the image below.
Warning
if you are using a 5mm LED rather than the illumination PCB, you must use a resistor in series with the LED to avoid drawing too much current. 
Wiring the LED with a missing or incorrect resistor may damage your Raspberry Pi.
