Lightweight Headlamp from Cheap, Readily Available Parts

Night skiing is really popular where I live, and while the ski resorts are adequately lit on piste at night, they are, obviously, not lit in the trees. Well, just because I can't manage to get to the resort during the day doesn't mean I shouldn't be able to enjoy a little tree skiing. Most commercial headlamps contain at least one if not more deal breaking issues, prohibitive pricing being one of those deal breakers. Home built headlamps can be really good, but often the designs I see online require the use of a lot of tools and ample shop space. Some of us are liberal arts majors who spend all our meager income on lift tickets and/or can't manage to hold on to one job long enough to afford to live in a house with a shop.

I don't have access to a CNC machine, a shop, or fancy tools, so I set out to design a headlamp that could be built in a spare bedroom of an apartment out of readily available parts that didn't require exotic tools or materials. Everything is available online and at either a good hardware store or a hobby shop.

The other considerations I had in mind are size, water resistance, and the ability to pocket the battery pack. The light runs off an inline resistor rather than an electronic driver so the input voltage can be 4.2 volts, which is the output of 4 rechargeable AA batteries. This is important because we skiers have to keep our batteries in our pocket so they stay warm, which means they have to be in a small enough package to fit inside a ski jacket pocket alongside snacks and a cell phone without making the skier look like a conspicuous shop lifter.

I also wanted the cabling to be cheap, detachable, and intrinsically strain relieved. That meant using RCA plugs for the power connectors so I could just use audio cables for the interconnects. This also obviated the need for a switch as I can just disconnect the cable when I want to turn the lamp off.

The whole assembly needed to not cannibalize straps and stuff from other headlamps. This meant I had to come up with a helmet mount that tilts as well. On top of tilting, it also needed be adjustable with gloved hands and able to be locked in place once at a satisfactory angle. I kind of like my solution, which is to utilize big ol' brass wing nuts and brass machine screws.

Here's a video of the headlamp in action at Skibowl.

Step 1 First, locate a heatsink and clean it

My first headlamp used a heatsink from an AMD Athlon 750. Well, since then processors have gotten increasingly powerful and no longer have heatsinks that are small enough to mount on a helmet. But, as processor heatsinks have increased in size, so too have the heatsinks mounted on the southbridge chipset, which is the littler one 'south' of the processor on the motherboard. So, when my partner's motherboard blew up, I scrounged the southbridge heatsink from it.

The first thing to do with any heatsink is to degoop it. The best way to get that adhesive plastic off is to scrape it off with a credit card. Try to use a sideways sawing motion to get it to curl up. It really helps to soak the whole thing with isopropryl alcohol to soften things up a bit before scraping.

After getting the adhesives off, use some of the most advanced degreaser available, dish soap, to clean off the thermal grease. I'm not joking about the dish soap. I've tried a lot of different chemicals, and nothing beats a good surfactant that's up to the task of getting bacon grease off of pyrex.  

Comments

[CobyHoff]

2 10cm lengths of 5/8" ID PVC pipe would hold the 4 AA's. That would be easy to waterproof. Or maybe the covered 4 battery holder from this link at Digikey.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SBH341AS-ND

[emihackr97]

Litium Batteries! they are great!

[josefski]

Thanks for the idea; I like lithium batteries, but one of my self imposed constraints is that it needs to use the most readily available, field replaceable rechargeables possible, so I think I'm stuck with the nimhs. Cheers!