LEDs
The diagram below shows 3 methods of identifying the leads on a light emitting diode (LED). The most certain of the three ways is to look at the internal shape of the metal plates - some LEDs don't have the flat on the body, and the positive lead is only longer if the wires haven't been cropped. However, note that some jumbo LEDs have these plates reversed. If in doubt just try it both ways - since an LED is a type of diode it won't harm it if the polarity is wrong. Refer to the suppliers catalogue for pin-outs of bi-colour and tri-colour LEDs.
The Positive lead (Anode) can be identified by:
Longer Lead
Smaller Plate inside LED
The Negative lead (Cathode) can be identified by:
Shorter Lead
Larger Plate inside LED
Flat on body of LED adjacent to negative lead
