LEDs: Light Emitting Diodes

[toman]

Triva and another reason to be pissed off: There is virtually no application where an LED is not superior to an incandescent light bulb. Production of LEDs is less expensive, uses less energy, and creates less pollution. LEDs use far less energy, last far longer, and produce far less heat. If we were to replace every light bulb in this country alone with an LED, we could shut down 17 power plants, produce significantly less pollution every day, and save enough money to give every American who wanted one a complete college education. The technology and ability to do this has been around for years now, and yet; how often do you encounter LEDs on a daily basis other than on your smoke detector? What the hell is going on in this country?!?!

[PEACE FROG]

Hi ! What kind of candle power can you get from LED. Enough to read by?

[delta9]

Unfortunately, I think it has a bit to do with size. I'm not an expert on the subject or anything, but if I recall correctly, for an LED to produce as much light as a normal lightbulb it has to be fairly large... Though I could be wrong.

I do remember in an electronics course I once took making simple circuit boards and such, a small LED (think pinkie-nail size) could easily be burnt out if you didn't have enough resistance between the power and the LED. There's still quite a lot of homes in the US that don't have properly grounded electecrical throughout the house - and only a small portion of those that do have any kind of house-wide surge protection.

... So maybe part of the reason why we don't use LEDs is because it would require every house have proper electrical systems, and every light fixture would have to have a surge protector - that's a bit expensive of an order!

On the other hand, with a potentiometer before the LED, every light in your house would also have an easy dimmer http://www.rumandcoke.net/merlin/emote/devil.gif.

So, as it is now, I guess we'll have to take flourescent lighting as a middle ground.

[shaggy]

The best LEDs are just approaching the efficiency of incandescent lamps, which is about 10 to 20 lumens per watt. LEDs of that efficiency are still much more expensive than incandescents if you want to get the same amount of lumens out of them. You need an array of dozens or hundreds of LEDs to get the same amount of light from a lamp like a 60W bulb or a 25W motorcycle headlamp.

A very high efficiency LED costs a dollar or two a piece. An array of 100 would cost $100 but would still have the same efficiency of an incandescent, which costs about a dollar.

LEDs have the advantage that they have a long lifetime, are vibration resistant, and compact. Incandescents have the advantage of putting out a continuous spectrum, which is easy on the eyes, and low cost. White LEDs are really blue-colored LEDs that have a thin layer of phosphor that emits another color of longer wavelength to give the impression of white. These white LEDs also deteriorate after so many hundreds or thousands of hours. Their light is not as comfortable to the eyes as incandescent light, similar to how fluorescents aren't as comfortable because they too do not emit a continuous spectrum.

Incandescents are becoming more efficient also. Research is being conducted on IR coatings for incandescents that reflects some of the IR light back to the filament to reheat it instead of being wasted. High pressure incandescents are also being designed that allow the filament to operate at a higher temperature (which gives higher efficiency) without the filament evaporating as quickly.

Fluourescents are about four times as efficient as incandescents and LEDs and last about four times longer than incandescents. One of the best things consumers can do to save energy is to replace incandescents with screw-in fluorescents. No modifications are necessary.

[shaggy]

One application of LEDs that's reasonable is tail lights and turn signals on motorcycles. LEDs are resistant to the vibrations, have a very long life, and the low voltage of the battery is more easily matched to the LEDs. The amount of light doesn't need to be nearly as much as household incandescent lamps, as it is directed in a cone toward the front or back of the bike and appears very bright, even if the number of lumens is relatively small.

Marker lamps for cars and swimming pools would be another application. The low voltage of LEDs around a pool has the advantage that there is no shock hazard. Exit signs in buildings is another good application for reliability and safety reasons.