Hi, I’m new here, but so far I’ve found a lot of great info and thought I could get some help.
I’d like to build a headlamp for caving mostly. I already own a Spark ST6 nw460, which is excellent but I’d like more light and have an itch for a DIY project. I also recently bought a XinTD C8 with a neutral white XML T6 and the tint is just perfect, making the spark seem really yellow and dim.
So here’s what I had in mind. I found the following enclosure, which seems ideal for cutting into two parts (with a jigsaw), one part of about 2cm (more or less) depth for the lamp, and the other part could hold 3 x 18650 batteries (with some padding).
The heat sink, which would be cut into shape, would replace the back panel; the LED bases would be glued to it (some kind of thermal adhesive, right?). I would use plexiglass in the front.
Here’s the LED and optics. I’m not sure which driver I need. I think 2 XML T6 LEDs (one with optic, one without) and the driver should fit inside the enclosure; if I can fit three LEDs, that would be great.
Beside the driver, also not sure what type of switch to get and how to waterproof it (silicone, a cork gasket).
So, what do you think? Any advice is appreciated.
sounds like a good plan, although it might be worth tweaking it a bit
Check out this thread
lots of interesting advice there.
I’d go with 2x 18650 if you can, 3 cells on your head is quite a lot (my helmet light has a 3 cell battery).
Don’t bother with those heatsinks, just get some L- or U-channel aluminium and use that. There are plenty of bike light builds using Hammond box enclosures, which use a similar principle. The only place you want fins is on the outside of the case, having them inside just adds weight.
Think about the driver. Simplest and cheapest would be a AMC7135 based driver with a Poorman’s set up to drive 2 LEDs from a 2 cell pack.
About optics. I wasn’t terribly impressed by the Carclo, but I do like the LC1 (without holder) and I’ve got some LED-DNA narrow optics to try which have been highly rated by the mtbr crowd. I’d go with 1 optic and 1 aspheric for throw - the optic will give you enough spill not to need a bare LED.
Judco switches off Digikey are excellent and you can buy rubber boots for them. Use non-acetic cure silicone (v. important) for the external joints. Lexan is good for front covers, although it does scratch. Glue it in using 5min epoxy. I’d use a cable gland (also off digikey), a magicshine 1m cable extension for the cable and plugs (waterproof) and marine tape followed by plastidip for the battery. Don’t forget a 2S PCB, ideally with balance function, and Panasonic NCR18650 (B, 3400mAh if you can get them) cells for the battery
I think that’s it for now!
edit: guess it wasn’t! Check out the Nichia 219 LEDs, they’re supposed to have superb colour rendering and are more or less as efficient as current Cree LEDs.
Wow, thanks for such a detailed response. About the heat sink, I it wouldn’t go inside, it would replace the back plate, with the fins on the outside (edit: I guess the lamp depth would have to be 1cm then).
I’ll go check out everything you mentioned. Thanks!
If that heatsink was thicker so you could tap a couple of threads and bolt it to the housing with some thermal paste in between, that might be worth doing. If not, I wouldn’t bother.
Have a careful think about thermals vs. brightness too. I’m not sure how cold it is down in a cave, but there’ll be a limit to the current you can drive those LEDs at in a housing the size you want. A very rough rule of thumb is 2sq.in. of surface area per watt, with some degree of air flow. So for 2 LEDs @1A, you’re looking at ~12sq.in. or so, which is quite a lot for something that’s going to be stuck on your head.
Well, I guess it would run on medium most of the time, with just short intervals of full power when there’s a need to illuminate the bigger areas. But I see the point, just looking at Stenlight s7 or Scurions, I see they have thicker bodies which probably take away heat faster.
+1 to Matt’s recommendation of MTBR… Lots of good stuff/ideas there for headlamps.
Couple of minor ideas to add. If you design a replaceable lexan front, then scratches won’t be as much of a curse. I’ve used 1mm silicone baking sheet material (smooth both sides — very important) from ebay as a custom gasket.
The hammond box would work; there are also lots of sled designs on mtbr to check out. One more possibility is the easy2led 20mm housing… it’s cheap and cheerful and very easy to turn into a headlight by plundering something like an old Petzl Zoom for donor parts.
I’d 2nd the Easy2LED housing, they’re easy (doh!) to work with and the new ones have an o-ring at the back for sealing. Ofroad’bent on mtbr has made a bunch for adventure racing with headband mounts. They do make the housing part very simple and if you can work into your plans an inline switch, that’ll make wiring it up a piece of cake too.
Do you wear a helmet caving? If so you might consider having the lamp in front and batteries in back. All in one it might hang up on top. Or maybe dual side lamps?
Well, that was the plan. The enclosure I found on ebay can be cut into two pieces, one for the lamp housing and the other for the battery pack (can fit 3*18650). And it’s got nice rounded sides, so it’s not ugly :bigsmile: .
