What Is An Led ?

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What is an LED  LEDs, or light emitting diodes, are an electronic light source. LEDs were first discovered in Russia in the mid 1920's however no commercial use could be found for them until 1962 when they were introduced as a commercially viable electronic component. Early LED's were manufactured from gallium arsenide and produced a low intensity red and infrared light. Now other materials are added to the gallium allowing the creation of shorter light wavelengths and varying colours. LEDs, like all diodes, are made of very thin layers of semiconductor material, one layer will have an excess of electrons, while the next will have a deficit of electrons. The LED consists of a chip of semiconducting material impregnated with other materials to produce the required colour. Current flows easily from the positive side - cathode or P-type, to the negative side - cathode or N-Type. This is commonly known as a P-N Junction. Charge-carriers, electrons and holes flow into the junction from electrictrodes with differing voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon The wavelength, or colour of the light emitted depends on the energy gap or bandgap of the materials used in the manufacture of the P-N Junction. LEDs are all manufactured from direct bandgap materials to produce light in the visible spectrum. Typcial indicator LEDs required very little power to operate, generally between 2V - 4V at no more than 20mW - 60mW (milliwatts), however in order to generate higher light outputs power consumption in general illumination LEDs, chips are now being developed up to 8W with the aim of replacing incandescent light bulbs. The increased power and light output does have its limitations and design considerations. Today's high power LED's require much larger semiconductor dies for mounting, and also needed specially designed heat sinks to remove the excess heat from the semiconductor. Heat drastically reduces the life expectancy of the diode. LEDs are the most efficient form of lighting available today. In 2002 LED manufacturer Lumileds released a 5W LED chip with a light output efficiency of 18-20 lumens/watt (lm/W). In 2003 Cree produced the first commercially available white LED with a luminous efficiency of 65lm/W. In 2008 Nexxus Lighting released the Array range of LED lamps, with a luminous efficiency of 105lm/W, the brightest, most efficient LED available commercially today. By comparison, halogen and incandescent lamps have a luminous efficiency of around 15lm/W, while fluorescent tubes produce 100lm/W. With LED manufacturing technology improving daily, it is easy to see why LEDs will be the lighting source of the future. Mike Brunt is a director of Specialized Lighting Concepts, and New Zealand owned company that has been at the forefront of fibre Optic, LED and solid state lighting technologies. http://www.specializedlightingconcepts.co.nz For more infomation on the Latest in Energy saving LED lamps see http://www.specializedlightingconcepts.co.nz/energyefficientlighting.php?category=165 [email protected]