Fifty years ago, people had already known the basic knowledge of semiconductor material can produce light. The first commercial diode produced in 1960. LED is short for light emitting diode (LED), its basic structure is an electroluminescent semiconductor material, placed on a stand with down-lead, and then sealed with epoxy resin around in order to protect internal batteries, and so the aseismatic capability of LED is good.
The advantage of LED illumination:
1 .Security: LED is supplied by low-voltage power, so it is safer than supplied by high-voltage power; it is particularly applicable to public.
2. Economy: compared with the incandescence lamp the energy consumption reduces 80%.
3. Applicability: convenient apply, each unit of LED snippet is 3-5mm square, it can be prepared into various shaped devices, and suitable for the inconstant environment.
4. Stability: it can work 100000 hours, the light decay is 50 percent of the initial.
5. Responds time: fincandescence lamps base on millisecond, the LED base on nanosecond.
6. Environment protection: no harmful metal mercury.
7. Color: changing the electric can change the color, the light emitting diode easily adjust the energy band structure and the band gap through chemical modification, adjustment of the energy band structure and the band gap and achieve multicolor luminescence. For example, with small current at the LED is red, but with the current increase, it will turn onto orange, yellow, and green finally.
8. Life span: the expectancy of LED is more than incandescence lamp; it is more than ten times as an ordinary incandescence lamp.