Part number	Datasheet
Farnell: 1581173	MULTICOMP, MCL034BGC, 510 nm
Mouser: 859-LTL17KTBS3KS	LiteOn, 17KTBS3KS, 476 nm
RS: 466-3532	Kingbright, L-7104QBC-D, 465nm

This component must be fitted the correct way round.

The positive connection is to the Anode, usually indicated by the component’s longer lead.

The negative connection is the Cathode, usually indicated by the component’s shorter lead and also by a flat area on the rim of the plastic.

LED position and orientation are typically shown on the printed circuit board as illustrated. In this case, the Cathode is on the right-hand side.