LED

Light Emitting Diodes are cool

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Anodes, Cathodes, Flat spots, long leads etc.

To make an LED light, current passes from it's anode (arrow part of symbol) to it's cathode (flat line) towards a lower potential (towards ground).

For a typical radial LED, the cathode is denoted by a flattened area of the rim and the anode by a longer lead.

Current needs to be limited, usually by a series resistor, although that wastes power.

Typically need about 1 - 10mA to light an LED, with a voltage drop between 2.0 and 3.4V.

External links

• Light-Emitting Diode at Wikipedia