LED light bulbs?

[Umfriend]

So which is the greenest ATM? I've replaced some bulbs with CFL's last year but need te replace some halogen lamps.

[Brian Ellis]

[Singh, J., 2005] Smart Electronic Materials, Cambridge University Press, ISBN 0-521-85027-4, pp. 238-243
This discusses efficiency, as well as the theory, and all the examples cited are Ga-As LEDs, although it does not specifically say that gallium arsenide junctions are the only ones that emit light.

In fact, the first LEDs did not; they used carborundum, but this is going back to 1907 (Henry Round) and 1922 (Oleg Losov). I believe some of the bright blue LEDs may use gallium nitride, but I have no reference to that in my library.

[DukeP]

Brian, Im not entirely certain that all LEDs contain arsenic.

Red LEDs often contain gallium aluminum arsenic - but red LEDs are rarely used domestically for lightning (red is such a lousy colour for illumination!).

Do you have some references with which to enlighten me (grin)?

~~DukeP~~

[Brian Ellis]

And all LEDs contain arsenic. So what?

[Wombat]

Depends on how 'green' you want to be; all fluorescents contain some mercury.

Yeah, but in most of the country, this is more than offset by the reduced fuel consumption and pollution at the power plant.

[DukeP]

I have 10 led spots and 4 "regular" led bulbs.

Theres a vast amount of tones to be had - personally I prefer a more bluish tone for my bathroom and a more yellowish tone for my corner lightning.

As for the "bulbs" - you do risc getting a greenish hue - thats usually a result of using a yellowish lamp shade.

This green hue have been my only problem - and thats an esthetical one.

Ive tested the various bulbs with my spectrometer. The problem seems to be, that the human eye observes green far better than blue and red - the intensity isnt higher (it is in fact around 25% lower).

The advantages is instant on. No need to wait for the old energy saving flourescent bulbs to start up. Another advantage is the complete lack of heat generated. Thta goes particular y for the spots. There is zero clearance needed, so they are much easier to install in drywalls with insulation etc.

I doubt there is much in the way of mercury in LED bulbs. Any kind of heavy metals needs to be reported - and the only thing worth noticing is some phospher in some of the tones.

Oh. And in Denmark they are prices at or around 10-15$ each. Guaranteed to last 40.000 hours (I do not know at what strenght tho - LEDs dont die - they fade away).

Just ask if You need to know anything more about the practical aspects and everyday use.

~~DukeP~~

[Dr Mordrid]

Depends on how 'green' you want to be; all fluorescents contain some mercury.

As for white LED's; blue/UV emission + phosphors is old school as there are 2 new techniques that work much better;

The first was recently announced by Bilkent U. in Turkey and is based on nanocrystals made from a core of cadmium selenide with a surrounding layer of zinc sulphide. Blue LED's are coated with a layer of these crystals. In operation the nanocrystals absorb some of the blue output and re-emit red and green. R+G+B = white, and at a rate of about 300 lumens/watt. Of course the trick is fabbing the nanocrystals.

The second was developed at Vanderbilt. In this version a blue LED is coated with quantum dots that glow white in response to the blue light from the LED. This produces a warm, yellowish-white light very similar to the light produced by incandescents.

[Wombat]

Why not CFL bulbs?

[Mehen]

Yeah I think I'll wait then. Thanks guys. I MIGHT get one for my room though, I don't need a whole lot of light, and I have a ceiling fan/light fixture, so the lights tend to burn out quicker (I guess its the rattling). For the rest of the house I'll hold off though.

[degrub]

1) no, the light is very directed, narrow beam. Only arrays of LEDs can give a "normal" beam width. Many of the "white" LEDs are using a phosphor to convert blue to white which cuts down on the light transmission significantly.
2) 50 USD + for the equivalent of a 75 watt par38 halogen flood light. The cheap ones tend to overdrive the LED and burn out much sooner than they should.
3) If they are inside a lens - about the same as a regular light bulb.

LEDs work great for accent or focused lights. Or where the cost of replacement is high and durability is low for a regular bulb. Think traffic lights for example. They pay for themselves very quickly, and it doesn't matter if a few die out of 50-80 or more.

Wait a couple years for the next generation to hit the market. Even if the price is the same they will be better "bulbs" and provide more what you are looking for.

[Tjalfe]

I have not seen one in person yet, but from what I am reading, none are using the latest and greatest LED's, so they are not as bright as they could be. Also, I am not sure the light is as nice and even as a regular bulb, considering it is made from oodles of directional LED's. Why don't you try one and let us know?

[Mehen]

I'm thinking of maybe getting a few LED light bulbs in the house.

I have a few concnerns:
1) brightness - will they be as bright, fill the room, etc, or will they be $$$ to get ones as bright as incandescent?
2) cost in general
3) How do they look? are they strange and distracting looking - and do you get used to it?