First-time Mod - Need some advice

[P220C]

Design parameters so far

Light's intended use:
- work-light for under counter work or assembling kids toys outside in the dark.
- room light/lantern for power failures

Output goals:
- Warmish tint (something like my Surefire E1b tint)
- 100 lumens +/-
- at least 2-3 hours regulated runtime

Host:
- DeWalt 18V light w/NiCad battery pack and flexible gooseneck and plastic case

Components:
- 3021-D-I-350mA BuckPuck
- Three emitters - bin to be determined
[strike]Cree XR-E LED (P4 bin???)[/strike]
- aluminum heatsink for led mount
[strike]3/16" steel for led mount/heatsink[/strike]



Questions:
Am I on the right track?

[strike]Do I need to add a chunk of steel to heatsink the buckpuck as well?[/strike] No heat sinking on buckpuck

[strike] Am I OK without adding ventilation to the case?[/strike] Case will be ventilated


Edits to show revisions after Vegas' answers

 

[VegasF6]

I don't know what the output of your E1B looks like, but if you want a warm tint led you want a warm tint led you may want something like the Cree Q3-5A or even the High CRI Seoul P4 such as this one:
http://www.mouser.com/Search/ProductDetail.aspx?R=S42180-S2virtualkey61510000virtualkey889-S42180-S2

Neither of those leds will supply 100 lumens at 350 mA however, nor will your P4. So, you will either need a higher bin led, or (and this is my recomendation) multiple leds. Or you could do something with a warm MC-E.

Steel is a very poor heatsink material, you will probably want to look into aluminum, and not just plate but an actual finned heatsink such as for a CPU. I suggest you experiment on the bench with that. Make sure you get plenty of ventilation in the head of that light, you will need convection to pull air across the fins so they can cool and dissipate the heat generated by the led.

Personally I am picturing 3 leds in the head with something like this: http://www.dealextreme.com/details.dx/sku.1916 for optics and a head something like the Tensor LED lamps that one enterprising member was re-selling. http://www.candlepowerforums.com/vb/showthread.php?t=225808&highlight=tensor+lamp

Of course there are many ways to skin a cat, that is just what I envision for whatever reason.

Here are some better pictures of the Tensor lamp heatsink.
http://www.cpfmarketplace.com/mp/showthread.php?t=185911

 

[P220C]

So it sounds like ventilating the case is a requirement - no big deal, I'll just drill some holes.

I can scrounge up a finned heatsink. (should I mount the buckpuck to one also?)

Should I order a 500mA buckpuck instead of a 350mA since I was really only going this conservative route to avoid ventilating the case?

Thanks for steering me on the project, I really appreciate it.

 

[VegasF6]

You shouldn't need to heatsink the buckpuck. It would probably run even cooler if your battery voltage was closer to your led voltage, another good case for multiple emitters but either way it will be fine.

As to what drive current, 350 mA, 500 or more, that comes down to how bright do you need it if it can be kept cool. 2 leds at 350 mA will give you more light and less heat than 1 at 700 mA but either way there is still a significant amount of heat to disperse. I wish I had a better answer for you but all I got is experiment on the bench first. Find your heatsink material and mount your led(s?) and come up with a power supply. Could be a bench top power supply, a computer power supply, a wall wart from something or even a car battery. Figure the appropriate amount of resistance required and test with a meter. A bench of 5 watt resistors are cheap. Ideally you want to keep your led junction temp in the neighborhood of 80-90C. If you don't have any fancy equipment for measuring temps your hand will do for now. Cook it out on the benchtop for ~30 minutes and if heatsink gets uncomfortably warm in your hand you probably need a better solution.

You are using the Dewalt XRP batteries, correct? I think they are ni-cads so discharge won't be a problem, but if using li-ion cells or nimh you will need to consider that as well, not over discharging them.

Wish I could just give you the right answers, but you will learn a lot during the testing period.