design help with luxeon star custom light!!!

I am soliciting help with a custom light I would like to make. I have to say that if it wasn't for Wayne Johnson at Electrolumens, I wouldn't even be attempting this project. I conversed with him over several days about his Maglite mods, and he was extremely helpful and forthcoming with information. I was going to buy one of his lights, but realized that it just wasn't what I needed for my application.

Here is my project: I am a canoeist and occasionally paddle at night. I am wanting to make a custom light that I can mount to the bow of my canoe and power it with a separate power supply. I wish to use 3 Luxeon Star/O's. I machine plastics for a living but I'm capable of cutting aluminum also. I am looking for recommendations for the best housing for 3 luxeons. I will machine it out of aluminum for heat sinking purposes. What I'm wondering is what size of aluminum housing I will need for proper heat sinking. I want to run the led's to get the most light out of them without overdriving them too much.

They would burn constantly all night long. Would I do better to set them up in a liner array, or is a circular array going to give the best light? I want to get the most focused light from them as possible.

I am hoping to get a dialog started with anyone interested in offering ideas on this project. Any sketches with dimensioning can be input into my cad system and I can then output jpegs for viewing as the housing progresses.

Thanks for input.

Welcome woodbender!

This has possibilities for more than just a canoe light ... with minor mounting modification it'd be great for bycycles. It also interests me as a viable alternative for a mast-mounted deck light on a sailboat.

Unfortunately, I'm not the person to help with your needs, but I'll look forward to keeping up with your progress on this project.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by woodbender:
I am soliciting help with a custom light I would like to make. I have to say that if it wasn't for Wayne Johnson at Electrolumens, I wouldn't even be attempting this project. I conversed with him over several days about his Maglite mods, and he was extremely helpful and forthcoming with information. I was going to buy one of his lights, but realized that it just wasn't what I needed for my application.

Here is my project: I am a canoeist and occasionally paddle at night. I am wanting to make a custom light that I can mount to the bow of my canoe and power it with a separate power supply. I wish to use 3 Luxeon Star/O's. I machine plastics for a living but I'm capable of cutting aluminum also. I am looking for recommendations for the best housing for 3 luxeons. I will machine it out of aluminum for heat sinking purposes. What I'm wondering is what size of aluminum housing I will need for proper heat sinking. I want to run the led's to get the most light out of them without overdriving them too much.

They would burn constantly all night long. Would I do better to set them up in a liner array, or is a circular array going to give the best light? I want to get the most focused light from them as possible.

I am hoping to get a dialog started with anyone interested in offering ideas on this project. Any sketches with dimensioning can be input into my cad system and I can then output jpegs for viewing as the housing progresses.

Thanks for input.<HR></BLOCKQUOTE>


You could consider mounting a nice big CPU heat sink on the back of your light. Some of the newer heat sinks are huge. The overall size of the light could thus be reduced.

I found that using 3 Luxeon Stars in series works fantastic with 12 volts. I used a 8 AA battery pack. Drawing only 1 amp, it puts out fantastic bright light. Each Luxeon Star is using 1 amp, as it was explained to me. In series, each LS is pulling 4 volts, but one amp. Anyway, it is the brightest light I've done yet, and would be great on a canoe. You could maybe have a low and a bright setting, to save energy, and use 8 'D' cells, for long battery use for your trip.

I wish I could cut my own stuff out of aluminum. I'm looking into getting a lathe and some other equipment. It costs a fortune to have a machine shop do prototyping.

If you work with plastic, can you make me a special battery holder, if I gave the the requirements. Email me if you have some ideas. [email protected]

Thanks
Wayne www.elektrolumens.com

I've been playing around with my new LS(my first homemade light of any kind) for a bow mounted canoe light.

\image{my picture}

The first image shows the unit put together and the second shows some of the pieces. I plan to run one LS with 4.5 volts. I will be using trailer hitch wiring that will come out of the back of the light. I am planning on filling the piece that the LS sits on with aluminum filled epoxy and have the wiring encapsulated for waterproofing purposes. The front lens will be siliconed in, so that the whole unit will be waterproof.

Will this setup provide proper heatsinking and will 4.5 volts provide the best light without adding resistors to the LS? If this works for my purposes, I will be making two more. I will use one with a constant burn and put a switch to the other two to come on as needed. My battery supply will be mounted in a waterproof box that will be located within my reach for switching on and off the lights.

If my box with my power supply is mounted 5-6 feet away from the lights, will this length of wire affect the brightness of the lights?

Thanks for any help.

Jeff

Looks like my picture didn't take. I'll have to figure it out.

Heat transfer can be a very complicated subject. In general, you want the largest surface area contact between your LS LED and your heat sink. You also want the largest heat sink available, and for the heat sink to have a lot of surface area (from fins, pegs, etc) between it and the air. If you are in an aquatic environment, I would not suggest forced convection (with a fan).

You want to be able to seal the lights in a water tight container. The container it self must serve as a heat sink or heat transfer device.

For focusing, the circular array seems to be the way to go. All of your LEDs have collimators, so you won't do much better than that.

The idea someone posted earlier about using a computer chip heat sink is great. Its exactly what they are designed for, and they are cheap. You need only align the LEDs onto the heat sink. If you are concerned about shorting your circuit, I would also design some way of sealing the LEDs, but keeping the heat dissipation side of the heat sink exposed to air.

Here is another attempt at a picture. Let me know what you think.
http://jbj.home.texas.net/ebay.htm

While there is quite a lot of copper there, you must increase the contact surface area to take advantage of it. If you see my thread on this forum about the Death Star and check out my web page, you will see what I mean.

The question that I haven't had the time to figure out is how thermally conductive the aluminum filled epoxy is? I assume you are talking about the putty epoxy that you buy in little tubes at home depot. They would seem like a great way to couple the LS to the copper body if it is good at transfering the heat

The following is a description of the epoxy that I have in my possesion.

BC7136 Heat Resistant Casting/Aluminum

Gray, low toxicity, aluminum filled, heat resistant epoxy casting resin. May be used at room temperature without post-curing. Working time: 85 min., and can be removed from the mold after allowing to set 24 hrs. at room temperature. May be cast to a thickness of 3/4 inch in non-conductive molds. This product was engineered to replace VCHD and MDA systems while retaining excellent heat resistance and low viscosity. Designed for consistent use up to 300°F.

I think I am going to go a different route with my canoe light. I'll know more in a day or two, but I have different thoughts on the housing and heatsinking issues.

jb weld is good for this.
comes in a 5 min version too.
it is steel filled.
i potted a ls into a pr base,soldered the pr into a metal reflector ring in a black&decker spotliter, then filled the rest of the cavity to increase mass.
at 550 ma it stays safe.but it settles at about 400 ma in a few min though.

So the JB weld conducts heat pretty well then? Is it electrically conductive also? I've been looking in to various ways to heatsink my ls to an 3c aluminum flashlight head.

I found this anecdote about using jb weld as a thermal epoxy.
http://www.overclockers.com/tips169/

I was thinking about this light.

1) It pretty much doesn't matter what arrangement of Luxeons you use; any 'flat' array where they are close together will produce essentially the same beam pattern. Think of the beam as a cone of light...three beams means three cones, each coming from a different starting point, but all pointing in the same direction and overlapping. At 20 feet the 1 inch difference in the overlap will simply vanish. So if a line or a ring works better, just use it.

2) A flat aluminium or copper surface works best for the Luxeon side of the heat sink. I would suggest making or buying a small hunk of finned aluminium or copper, or some other pre-made heat sink, with a flat face, and mounting the Luxeons on that. I'd then suggest using your plastic working skills to make a transparent cover that fits over the Luxeons and seals against the flat surface of the heat sink.

3) The seal can be permanent. You won't need to change the bulbs

-Jon

woodbender,
Have you given any thought about water-cooling your canoe light? I'm referring to using aluminum or copper as your mounting heatsink for your luxeons, but maybe you could put an aluminum or copper "box" or "cup" (or whatever) to pour water into, coupled to your mounting heatsink. I don't know what kind of canoeing you're doing (lake or stream), but it just seems to me to be such a viable choice to use water to cool the luxeons. You might even "change water" during the night to keep them good and cool. The specs for the luxeon show that the cooler you keep the junction temperature the brighter the light is for any given voltage and current. I've seen the specs at Mark Hannah Surplus. www.markhannahsurplus.com

Hope my two cents worth has been helpful!

Here comes another one of my big ideas...

Some sort of flowing water cooler powered just by going through the stream! As with all my big ideas though...don't know how you'd do it.

CPU thermal compounds are designed to transfer hear from hot CPUs to heatsinks. My fav. is Artic Silver although some others have other faveroites, it actually will work it's way into the microscopic pits on the heatsink for most effective heat transfer...much better than plane ol' silicon based stuff. The thing to remember with thermal compounds is that a thin layer between your CPU (Or rather...LED) will transfer heat much much better than a thick layer, so the closer you can get the LED to your heatsink...the better.