Leds = cold light?

After learning about LED's and such, and reading about crazy people overdriving LS's and what have you..

I wonder, aren't LEDS suppose to be cold light? i.e. no heat? What's with all this heatsinking. (either than a fact that it's cool to overdrive the LS way over factory specs to make it brigher)

YC

No, you mis-understood

LED's are COOL light!

Like, "hey man, that's cool!"

Just kidding.

My "lay" answer (and there are many people here more qualified than me to answer this), is that LED's do not get AS HOT as compared to traditional incandecent bulbs.

Kind of like saying "I put synthetic oil in my car, and now my engine is running cooler". Well, if one said this, the engine is still hot, but maybe not as hot as a comparable engine.

That's my thoughts.

Anything that takes in energy (or should it be power?) must put an equal amount of energy out. One of the basic laws of physics. So, even though an LED doesn't have a hot glowing filament it still produces heat. If a light source is 10% efficient, 10% of the input energy will exit as light, the other 90% as heat. An LED and a halogen of equal efficiency and wattage will produce equal amounts of light and heat.

Perhaps the idea of LEDs beeing cool light comes from the fact that they have traditionally been very low wattage devices.

The light that LEDs put out is cool, i.e. no IR . Incandescent lights put a lot of heat into the light.

In either case, the energy not converted into light, (they have similar efficiencies), is converted into heat. The primary difference is that the heat from the LED has to be dissipated via a heat sink.

Another difference is that incandescents are designed to operate at very high temps. LEDs will break down if their max temp is exceeded.

LEDs are also 'cool' because the energy wasted as heat is wasted as heat at a lower temperature. The filament in a lamp can hit 3000+ degrees (C), but the junction in a Luxeon has to stay below 125 degrees. Filament lamps get more efficient when the filament gets hotter, LEDs get more efficient when the junction gets colder.

But LEDs still waste electricity in the form of heat, and that heat still has to go somewhere.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> filament in a lamp can hit 3000+ degrees (C), <HR></BLOCKQUOTE>

I can verify this! I plugged the little bulb from a 2 AA mini-mag into a 4AA NiMH battery pack. It was about as bright as a single luxeon. Stupid me grabbed the bulb to pull it out of the connector, and now I have small 2nd degree burn spots on my thumb and index finger

The bulb was dumping out WAY more heat than the luxeon, for the same light output. (hence, the luxeon is a cold light )

That'll learn me!

-Darin

The light from an incandescent is a product of the heat generated. Unfortunately, a large amount of the heat is not converted to light.

The light from a LED is not a product of the heat. The heat is a product of the inefficiency of the system. Fortunately the heat generated is relatively moderate. Unfortunately the "moderate" heat is damaging to the LED unless removed through some sort of rapid heat dissipation system.

The LED when driven at peak efficiency isn't very bright. When driven at inefficient levels it's brighter.

It's interesting that efforts to bring the LED to performance levels of the incandescent is bringing us ever closer to the inefficiencies of the incandescent.

As Spock would say..."fascinating".

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Empath:
It's interesting that efforts to bring the LED to performance levels of the incandescent is bringing us ever closer to the inefficiencies of the incandescent.

As Spock would say..."fascinating".

<HR></BLOCKQUOTE>

Empath,

Are part or fully Betazoid?

Even if the "inefficiencies" of LED's someday equaled incandecents, that would still be a plus to use LED's, assuming that someday they can throw far like incandecents.

There will most probably have to be "spot" and "flood" LED's, or, since LED's don't need a reflector, you could have two, one for distance spot, and one for local flood.

Oh cool

Wouldn't that be cool to have one light that gave you both, at the same time, that wide, white, even, flood that we have come to expect from LED's, and a nice spot to go the distance?

It could be done.... make a LED with an emitter that's a cylinder, facing a nicely focusabe reflector. It'd have 10-20 times the surface area of a LS, but.....

Or just design a decent reflector for the Luxeon Star!

Take a look at the output of a SL Scorpion, a decent spot with an even flood beam.