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RE: [APD] If it's good for street light...


This it´s true. The efficiency of a no-red LED it´s low and the "white" LED it´s the worse. The "white" LED have application when we
need a cold, pulsed and durable light source, but they are inefficient to light something compared with gas discharge lamps. Well,
at least in these times...

Néstor D. Groel

> -----Mensaje original-----
> De: aquatic-plants-bounces at actwin_com 
> [mailto:aquatic-plants-bounces at actwin_com] En nombre de S. Hieber
> Enviado el: Martes, 19 de Julio de 2005 09:34 a.m.
> Para: aquatic plants digest
> Asunto: Re: [APD] If it's good for street light...
> I'm not really up to date on the superbright LEDs, but I'll 
> share what I know.
> The photon that is emitted in fluorescent bulbs is a UV 
> frequency, when the UV photon hits the phosphor paint it is 
> absorbed by an electron, which is then unstable and emits a 
> photon but at a lower wavelength. The wavelength is, to put 
> things crudely, a function of the kind of phosphor.
> In the LEDs the electrons are roaming around all the 
> molecules in the crystal but they each still have a specific 
> energy level so exciting them kicks out a photon. 
> In super bright LEDS, the crystal is doped and their is a 
> secondary emmission of a photon stimulated by the first, sort 
> of similar to the UV photon striking a phosphor in a 
> fluorescdent tube lamp except that there is no plasma 
> (conductive gas) involved, it's all solid state.
> Unless the LED is really fancy, the output comprises 
> relatively small portions or spikes of the visible spectrum. 
> But they are broad enough to be useful. You can put a red, 
> green, and blue LED in combination and reasonably white 
> light, much the same way your TV makes you see white.
> The type of material with which the super bright LED is doped 
> determines whether it's a green, blue, white LED.
> I believe that various colors of LEDs are possible without 
> the doping but most, other than the classic red, are very low 
> output. What made the superbrights the next big thing is LEDs 
> was the idea to dope the diode, to create fluorescence in a 
> solid state device. I'm sure what I've said terribly 
> oversimplifies the whole matter.
> Also check out this page, especially the part of the page 
> called ": How do those white LEDs work anyway?":
> http://ledmuseum.home.att.net/reserved.htm#q11
> Hope that helps,
> Scott H.

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