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white LED!!! light source!

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dolby86

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hi
i m a student ................n trying to find about this stuff!

hw it sounds by usin white LEDs we can get a light?
concept is to use bunch of white LEDs emitting clear white light! with minimum voltage
wanna know about the wht LEDs also!

is it economical n efficcient???
waiting for opinions
suggestions are welcome!
many thanks
sai
 
From what I know a white LED contains RGB LEDs in one package, that mix to produce a white light. It became available shortly after the blue LEDs were manufactured. They are fairly efficient, much more so than incandescant, and probably halogen alternatives. The light is much less orange then that from an ordinary bulb, it tends to look slightly blue, similar to a halogen.
 
LEDs produce light of a single frequency based on the jump of electrons between the various electronic band gap. Since white light is not of a single frequency, but rather combination of light of various colors, strictly speaking, there is no such thing as white LEDs.

"White" LEDs can be produced by how Dr EM says, or it could shine single-frequency light onto a phosphor coating to produce the white light.
 
The phosphor method is beter since it gives an musch beter light.

The Red,Green and Blue diodes make an white light but you can see the colors.

The phosphor this is simply an blue LED that has yelow phosphor poured over its emiting chip.
 
Yes and it isn`t simple getting white light from a multicolor LED.
 
The phosphor this is simply an blue LED that has yelow phosphor poured over its emiting chip.

Maybe thats why my 1W white LED looks yellowish when it is not on.
 
On most LEDs with a clear case, you can see the chip inside when they are off. When a white LED is actually a blue one with a yellowish phosphor over it, you can't see the chip inside.
 
zachtheterrible said:
The phosphor this is simply an blue LED that has yelow phosphor poured over its emiting chip.

Maybe thats why my 1W white LED looks yellowish when it is not on.

Some white LEDs have a piss-yellow cast, but others with a higher color look quite bluism. Both are phosphor white LEDs. The 3-chip method is rarely used anymore. Different color technologies use different voltages and currents so balancing them is difficult, they cannot be put in series or parallel. Most likely they will need to be used with resistors and designed for a particular source voltage. Mfg then involves 3 different technologies put together, and you're trying to focus 3 different sources of different colors. They won't focus exactly together and it can mean the color content may vary across the field of view.

You don't say what you want to do. White LEDs have been around a long time now and have been widely used in both high end and basic consumer products. They are "efficient", well sort of. Less efficient than flourescent and sodium vapor or metal halide lights. So not only expensive but less efficient for room lighting unless you need to do a focused cast that is difficult to do with flourescent.

Incandescent bulbs, halogen ones too, do not scale well and get REALLY inefficient in flashlights. LEDs scale just fine and are many times more efficient in this area.
 
Yelow adds the mising components of white.Blue is provided by the LED chip it self.The blue light exsites the phosphore that emits red and green (Tose two togeter are yelow)

Thats why white LEDs give a litle blueish light (I like it more than an yelowish light from an norman bulb)

Flourescent lamps use the exsact same thing to make white light.But there phosphor makes blue too since its exsiting it whith UV.

You cod try to look at an flourescent lamp reflection in an CD.You will see violet (The UV made my the mercury vapor that makes the phosphor glow),red,green and blue (The simulated white light) Wen i once drived an compact flurescent bulb (those that you screw in insted of normal bulbs)I cod see the blue/violet light from where the flagments are since there is not phosphor there.
 
The tolerance of the color from the phosphor coating in a white LED isn't perfect. Agilent (a spin-off from Hewlett-Packard) "bin" their LEDs into different brightness part numbers and the tint of their white LEDs. Then in an array the LEDs will all look exactly the same.
 
Speking of exsactly the same Those water clear lenses can be a headace if you got all the difrent LEDs mixed up.You dont know its color if you dont light it up.Iw solved this problem by marking them on the botom whith color pens.That way i know what color is it just a looking at it.
 
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