DIY LED Canister Lamp

[kubi]

Hi,

Interesting design for the 3 leds.
I'm trying to build a lamp with 3 SSC P7 as well. I've found a mirror that can fit the 3 leds and a lamp (ultrafire wf 500). So everything was good. Until the first heat stress test

When the leds are closed into the lamp the soldering starts to melt within 3-4 minutes of operation. It seems that the heatsink I've put on the leds is not enough.
Now I'm planning to use some liquid, like transformer oil, but I do not know how to choose a proper one. It must not be agressive to the electronic parts and the glue I use to seal the lamp.

Do you have any idea?

Btw, I use 18650 Li-ion batteries, 3x3 (parallel x series), that are ~2200-2400mAh each with 2 PCB boards ( dealextreme sku.3178 )

 

[bronk]

melting the solder is a very definite bad sign. You are way over the allowed junction temp for the LEDs. You are lucky they are not ruined already.
The P7s will dissipate about 10 watts each if running at spec (3.7 v at about 2.8 amps each). Put 3 together and you have 30 watts. This is probably as much heat dissipation as the soldering iron you used!
If I got the number right, the DX3178boards are current regs with 1.4 A each. I assume you are running them in parallel for a total of 2.8 A.

You then need a heat conductive material for the heat sink. Try an aluminum or copper disk about a half inch thick that is a snug fit into the housing. You are trying to get rid of a significant amount of heat. To convince yourself, put the soldering iron inside of the housing for 5 min and then try to pick it up...

Oil will help a little, but you really have too small a space for significant convection - therefore little to no oil current movement. Without the convection, there will be little additional cooling. Plus the oil will mess up your optics. You can try just dunking the whole lot in mineral oil. It will help prevent leaks at depth as well, but still is a mess to deal with. many years ago I worked in x-ray equipment field service and got truly sick and tired of dealing with transformer oil.

Put an ammeter in the circuit to see how much the leds are really drawing. If you get 2.8A then life is good (assuming 2 of the boards you mentioned in parallel).

 

[DIWdiver]

Kubi -

The best way to get rid of heat in a dive light is through conduction. Aluminum and copper conduct heat way better than almost anything else you could use (over 10 times as well as stainless steel, which is way better than oil or plastic). Copper is better, but harder to work with. IMHO, the best design is to have the heat go from the LEDs to an aluminum plate to an aluminum body to the water. An alternative is to take it out the front of the lens like one of the big manufacturers (UK, IIRC) is doing, using a metal column that goes from the LED plate through the lens and into the water.

If you can't use an aluminum body, then the next best thing is to spread the heat out over as much surface area within the light as possible, and getting as close to the case as possible. For 20-30 watts you're talking a lot of area. Depending on the material and thickness of your case, and how well you get the heat to the inside surface of the case, you could be talking 2-4 square inches PER WATT or even more to keep the LED below max temp at rated current.

There is a special material made for conducting heat from one bit of metal to another when there isn't quite enough contact. It's called heatsink compound, and should be available from various electronics distributors. I'm sure DigiKey and Mouser stock it.

Ideally it should be used VERY sparingly. Your parts should fit well enough to pinch hairs, and this material should fill the very small gaps. As it is very messy, it should be put between parts that won't have to be taken apart. It's very sticky like honey, but just thick enough that it won't run.

Hope this helps.

D

 

[350xfire]

Hi,

Interesting design for the 3 leds.
I'm trying to build a lamp with 3 SSC P7 as well. I've found a mirror that can fit the 3 leds and a lamp (ultrafire wf 500). So everything was good. Until the first heat stress test

When the leds are closed into the lamp the soldering starts to melt within 3-4 minutes of operation. It seems that the heatsink I've put on the leds is not enough.
Now I'm planning to use some liquid, like transformer oil, but I do not know how to choose a proper one. It must not be agressive to the electronic parts and the glue I use to seal the lamp.

Do you have any idea?

Btw, I use 18650 Li-ion batteries, 3x3 (parallel x series), that are ~2200-2400mAh each with 2 PCB boards ( dealextreme sku.3178 )

This is why I built my light head out of a chunk of aluminum and never run it for extended periods of time outside of water.

 

[lucca brassi]

heat conductive compound-adhezive

Arctic Silver, Inc. - Products

recomendation on ARCTIC SILVER or ARCTIC ALUMINA both they have low or not resistance . They can be bought on local computer or electronic shop for use on computer heatsinks.( not processor-because it is very difficult to unglue away.

I agree partial with 350xfire

This is why I built my light head out of a chunk of aluminum and never run it for extended periods of time outside of water.

Not for chunk of aluminium , but that must be head designed for power led or led's. I mean that must be body of head and fastening surface for lead from one piece. Cooling ribs a welcomed!

The definition of best cooler is low weight with large surface ( to provide conduction /convection (in that case aluminium -water ) ) Critical place it is direct under led . I don't need to preserve heat energy in metall and transport it to the long distance of cooling ribs , Better idea is to drill hole through aluminium under led to let water flow to to lead away heat.

 

[bronk]

Finished a second light. This one is for my wife. This one uses a regulator board with 3x AMC7135 from Dealextreme. This is very small and inexpensive. It can be mounted in the light head. however it does need to have an added heat sink (gets too hot otherwise). Using a piece of copper flashing, soldered to it and then to the reflector screw does the trick. First dives today. She is very happy with it. However, we will be refining the handle mounting. It has to accommodate her fused thumb joint.