LEDs

LEDs are light emitting diodes. A light-emitting diode or LED is a semiconductor light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness.

According to encyclopedia, the LED was invented by four independent American research groups in 1962. But the latest edition of Nature photonics reveals that it was actually discovered by a little-known Russian genius around 40 years earlier by Oleg Vldimirovich Losev.

LEDs emit light when an electric current passes through them.LEDs must be connected the correct way round, the diagram may be labelled a or + for anode and k or - for cathode. The cathode is the short lead and there may be a slight flat on the body of round LEDs. If you can see inside the LED the cathode is the larger electrode. LEDs can be damaged by heat when soldering, but the risk is small unless you are very slow. No special precautions are needed for soldering most LEDs.

LEDs do dozens of different jobs and are found in all kinds of devices, for example numbers on digital clocks transmit information from remote controls, light up watches and tell when appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.

LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. LEDs are thus more energy efficient and less expensive to use than the traditional incandescent bulbs which in turn helps in environmental sustainability.