Light Emitting Diode

Light Emitting Diodes (LED) come in different colours, shapes, sizes and brightness. The more common colours being red, green and yellow.

They are also available in bi-colour and tri-colour versions. Round ones come in 3, 5 and 8mm sizes. There are also rectangular, square and bar types.

Flashing types are available and seven segment displays are made of a number of LEDs in a particular pattern.

LEDs are easily damaged by excess current therefore it is normal to connect the LED to the supply via a series current limiting resistor. The value of this resistor is not critical but is usually within the range 100 - 330R.

Polarity must be observed when connecting LEDs (it should be noted that LEDs are damaged by reverse biased voltages larger than about 6 volts).

The Anode is connected to the positive supply via the limiting resistor. The Cathode is connected to the negative supply.