Light-emitting diodes (led’s)

An LED is often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern.

Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were also of low intensity, and limited to red. Modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent bulbs. They were soon packaged into numeric readouts in the form of seven-segment displays, and were commonly seen in digital clocks.

Recent developments in LEDs permit them to be used in environmental and task lighting.

LEDs have many advantages over incandescent light sources including –

• Lower energy consumption,
• Longer lifetime,
•  Improved physical robustness,
• Smaller size, and
• Faster switching

Light-emitting diodes (led’s) are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera flashes. However, LEDs powerful enough for room lighting are still relatively expensive, and require more precise current and heat management than compact fluorescent lamp sources of comparable output.

LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology.

Flashing led

Most flashing LEDs emit light of one colour, but more sophisticated devices can flash between multiple colours and even fade through a colour sequence using RGB colour mixing.

Bi-colour LED

Two different LED emitters in one case.

A decorative garden light that changes colour.

Tri-colour led

Three different LED emitters in one case. Each emitter is connected to a separate lead so they can be controlled independently.

RGB led

Tri-colour LEDs with red, green, and blue emitters, in general using a four-wire connection with one common lead.

Decorative multicolour led

Incorporate several emitters of different colours supplied by only two lead-out wires. Colours are switched internally simply by varying the supply voltage.

Alphanumeric led

Available in seven-segment, starburst and dot-matrix format. Seven-segment displays handle all numbers and a limited set of letters. Starburst displays can display all letters. Dot-matrix displays typically use 5x7 pixels per character.

Digital RGB led

These are RGB LEDs that contain their own "smart" control electronics. These are connected in a daisy chain, with the data in of the first LED sourced by a microprocessor, which can control the brightness and colour of each LED independently of the others. They are used in strings for Christmas and similar decorations.