heat from a led?

im working on a mod for an airsoft guns LEM unit, and im trying to fix a better bulb into it. i have the surefire 9P flashlight with the P91 bulb, and it gets really hot. i saw some LED replacements online, and i was wondering, do those get hot/as hot as the xenon versions? thanks!

I also have the Surefire 9P and I put the Cree R2 Drop-In 1-Mode LED Module (3.7V~18V / 26.5mm x 29mm) from Dealextreme. As far as I can tell, it does not heat up nearly as bad as the P90 or P91 incan lamps. However, I haven't run it for extended periods of time. I actually have a night firearms class tonight and tomorrow night and plan on using mine. I'll let you know how it goes. The one I bought from Dealextreme.com is $13 and change + free shipping, and for that price, you can't go wrong.

It should get warm. That's a sign that there is a good thermal path.

I don't think it should get as hot as the P91.

:welcome:

ive read some design pictures of the led bulbs, seems like theres a heatsink in the back that takes the heat. does the light beam get hot at all? im planning on using a plexiglass or standard plastic lens cover.

The heat in the incandescant lamp is nearly all coming from the filament in the form of infrared radiation (the head you can feel by putting your hand in the beam), so the lens material will matter. LEDs in the other hand, emit much less infrared radiation, but instead can heat up thanks to the circuitry that regulates and drives the emitter. So instead of having heat radiating in the same direction as the visable light, you get heat near the light source itself (inside the light); since there isn't nearly as much heat traveling directly to the lens, it is unlikley at best that that the lens material will matter.

Any particular reason for the plexiglass cover? A standard UCL lens should be just fine and will allow about 10% more light to pass through it. Like Elgreco stated, the LED doesn't throw enough forward heat for it to matter either way. The back of the LED emitter get's hot but that shouldn't be a concern.

http://flashlightlens.com/

wow you guys answer fast. well, my last question is, how would it work with a regular 9v battery compared to 3 C123 batteries, since im gonna be fitting a 9v battery into the unit.

oh, didnt see that link. nice, i think ill pick up that UCL 22.0mm one. perfect. thanks!

I doubt it will work long if at all. Capacity of a non-rechargeable 9v alkaline is maybe 200mAH. They're designed for very low drain devices. Maybe you can get away with one of the very low power modules like the M60LL that draws less than 200ma from the batteries. Even then due to the higher than normal drain you may not get the theoretical 1 hour of runtime.

Depending on the drop-in, you might be able to use 3 RCR123s(rechargeable CR123 sized batteries, usually 3.0v or 3.7v).