WHAT IS LED
Light-emitting diode is an electric component that emits light when connected to direct current. It works on electroluminescent principle and can emit light in visible specter as well as in infrared and ultraviolet.
HISTORY OF LED
In 1907 the British experimenter in Marconi labs Henry Joseph Round noticed for the first time that when a potential of 10volts is applied to carborundum (silicon carbide) crystal, it emits yellowish light.
The same year the Russian Oleg Vladimirovich Losev observed light emission from carborundum point-contact junctions.
The French physicist Georges Destriau discovers light emission in zinc sulfide. In honor of the Russian physicist, he calls the effect "Lossew light".
In 1955 the Rubin Braunstein reported that some simple diodes emit infrared light when connected to a current.
In 1961, Gary Pittman and Bob Biard found that that gallium-arsenide diode emits infrared light every time it is connected to current. They received patent for infrared LED.
In 1962 the American Nick Holonyak, Jr. invented the first visible-spectrum (red) LED.
In 1972 M. George Craford, invented the first yellow LED and a brighter red LED.
In 1976 Thomas P. Pearsall developed high brightness LED for use with fiber optics in telecommunications.
In 1979 the Japanese Shuji Nakamura develops the first brilliant blue LED.
Advantages are that they emit more light per watt.
Can be switched on and off unlimited and has immediate reignition.
Their lifetime is much longer than lamps, usually about 50.000 hours. After that continue to operate with reduced brightness.
The lighting fixture functions, even if there is any problem with some of the LEDs.
Maximum reliability even under adverse ambient conditions. Unbreakable.
Zero maintenance and replacement costs.
Minimium heat load emission.
Eco friendly. Complete absence of toxic substances(mercury, lead).
Resistance to voltage drop.
Choise of many types of beaming.
Choise of colour temperature(KELVIN).
In 2012 in the USA saving about $650 million in energy costs. Is calculated that if they change to LED lights over the next twenty years: a) they could save $250 billion in energy costs, b) reduce electricity consumption for lighting about 50%, c) avoid 1,800 million metric tons of carbon emissions.
By 2030, it's estimated that LEDs will account for 75% of all lighting sales.
LEDs are here to stay.