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matt151617
07-27-2008, 20:00
LEDs definately do not generate heat...

Salvo Rebel 21 Watt LED Dive Light, Dive Lights, Salvo, Salvo Rebel 21 Watt LED Dive Light (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=SalvoRebel21WattLED)

The battery may generate heat, but not a LED.

NeveSSL
07-27-2008, 20:16
Are you serious bro?

LEDS produce quite a bit of heat. If you don't believe me, google Solaris. :)

Brandon

NeveSSL
07-27-2008, 20:21
Found some good info: LED Thermal Management Basics (http://www.lunaraccents.com/educational-LED-thermal-management.html)

Why do you think LEDs don't produce heat? I've not heard that one. And they definitely do. :)

Brandon

mitsuguy
07-27-2008, 21:23
I am actually going to be building a 12 watt LED (ordered the stuff yesterday), and may possibly be building a 21 watt led based on the same/similar emitter that they used... thermal management is the most important part of LED head design...

here's the 740 lumen light I'll be using (the salvo is 1100) - DealExtreme: $23.16 SSC P7 W724C0-BSYPI 3.6V~4.2V 12W LED Emitter (Bare) (http://www.dealextreme.com/details.dx/sku.11809)

Once I get it up and running, I might just make a 3 led head...
again, heat sinking is the most important part...

No Misses
07-27-2008, 22:05
These are not the little LEDs that you played with in your Radio Shack Electronics lab kit. These are >3 watt LED emitters.

P=I*E (Power in watts = Current in Amps x Voltage)

matt151617
07-27-2008, 22:45
Well, I thought the basics of LEDs was they didn't use much energy, and had almost no waste (heat). I guess these super high output ones must sacrifice efficiency and life for higher light output.

NeveSSL
07-28-2008, 04:23
They are pretty efficient for the most part, but that doesn't mean they don't put out heat. ;) Especially, as you said, for the larger power LEDs.

Brandon

divinginn
07-28-2008, 17:27
the p 7 led is 4-3 watt chips built onto one chip,and they do heat up,but for a alum flashlight with a proper heatsink in the water there should be no problem. I just built two of them,one for diving and one beating around the house,no problems with overheating.I put both of them in maglights,d and c cell.

mitsuguy
07-28-2008, 20:22
the p 7 led is 4-3 watt chips built onto one chip,and they do heat up,but for a alum flashlight with a proper heatsink in the water there should be no problem. I just built two of them,one for diving and one beating around the house,no problems with overheating.I put both of them in maglights,d and c cell.

from what I had read, that was what I understood as well... There are lots talking about it being a super hot light, but not under the water... water is such a great conductor...

aggie99
07-28-2008, 21:07
Have you ever seen a LED replacement light bulb? The have huge heat sinks around the light source. I talked with a rep from Color Kinetics (an architectural LED manuf.) and he was telling me that the biggest issue they face with higher LED output is handling the heat. Because they are a diode they are just like computer parts and are very intollerent of heat and is the biggest factor in reducing their life.

matt151617
07-28-2008, 23:58
the p 7 led is 4-3 watt chips built onto one chip,and they do heat up,but for a alum flashlight with a proper heatsink in the water there should be no problem. I just built two of them,one for diving and one beating around the house,no problems with overheating.I put both of them in maglights,d and c cell.


The Mags are sealed enough for diving with, or did you make them more secure?

zahgurim
07-29-2008, 08:10
I've rigged up my own LED lights for night rides on my bike. You definatley need a heatsink with a given amount of surface area, or your LEDs are toast.

I imagine that LEDs for water use could have a much smaller surface area on the heatsink, given that the thermal conductivity of water is so much greater than air.

You guys have me wanting to rig an underwater flamethrower up now... :)

NeveSSL
07-29-2008, 17:19
the p 7 led is 4-3 watt chips built onto one chip,and they do heat up,but for a alum flashlight with a proper heatsink in the water there should be no problem. I just built two of them,one for diving and one beating around the house,no problems with overheating.I put both of them in maglights,d and c cell.

Ok, divinginn.... spill your guts. What all did you do to make your diving light? :D

Brandon

divinginn
07-29-2008, 21:34
I cut the maglight right behind the switch,ground off the threads on the light head and epoxied it to the tube,I replaced the stock plastic lens with a glass lens and used a smaller 50mm lens under the 52 mm lens and putting a o ring around the smaller lens to seal out the water,it is still in the experimental stage on the dive light,it held out water in the sink but I am going to take it diving this weekend minus the led to check out water proofness,if that works out I will build a canister for it. for info on building the maglight try googling diy dive light and for info on the leds check out candle power forums,they have many how to articles on modifying flashlights.It was very easy to do a regular flashlight conversion to a p-7 led,but trickier to waterproof the light but is has been done many times by others.

NeveSSL
07-29-2008, 21:40
Awesome. Thanks for the reply. I may google in a bit and see what I can find out. :)

Keep us updated! Maybe you could even start a new how-to thread. :)

Brandon

divinginn
07-29-2008, 21:50
It is awesome bright,it should outshine 10 watt hids with a smaller battery pack.

mitsuguy
07-29-2008, 22:52
here's my buildup that I'm working on...

http://forum.scubatoys.com/diy/15794-12w-led-can-light.html#post208242