Jan 5, 2009 - Electronics    Comments Off on DIY Bicycle Light Update

DIY Bicycle Light Update

OK, so I finally finished my DIY LED bike light using the 3-LED Cree XR-E design from www.bikeled.org. I rode with it last Tuesday night on the Natchez Trace ride with some HBC members. In summary, it’s impolitely bright. Running at 1000mA, it’s very much like car headlights, and even brighter than some of the headlights of cars that passed us. Most of the time, I rode with it dimmed down to 500mA or 350mA modes.

Other comments – I bought the Cree XR-E star boards from DealExtreme. The parts came in fairly quickly, considering they came from Honk Kong. I saw in the latest DigiKey catalog that they’re now carrying Cree.

Also, the TaskLED nFlex is a very small board. But, the fit is still very tight inside the square aluminum housing. Packaging seems to be the hardest part of building a light like this. The setup is a little confusing at first, but it doesn’t take much fooling with it to figure it out.

I bought the lenses from led-spot.com, which is some subset of another company. But, the lenses were relatively cheap and it was a good experience. The only complaint I had was I had to grind out sections of the lens to make room for the solder connections on the star. Be careful laying out which pads you’re going to use. BTW – I don’t have a Dremel, so I mounted a dremel bit in my drill press and spun it up to high speed. It cut the plastic lens like butter. I wore my face mask and I recommend you do too.

Speaking of lenses, I use two 5 degree and one 20 degree lenses. They throw a very nice pattern. I also have the 25×5 which I intended to use for commuting so cars can see me from the side. But, I think there’s enough light scatter to do the job. And I’m pretty dang reflective.

Arctic Alumina Adhesive is VERY cool stuff. It appears to be very good epoxy, and it’s very heat conductive. No, it doesn’t take much if your parts fit well.

I also took an old POS mag light adapter and chopped it up to improve the mount. It’s a gadget that has two velcro straps and a rubber thing in the middle. One side holds the mini mag light, the other side holds the handlebar. I cut the rubber thing in half and siliconed it to the L-brackets so the lamp assembly mounts properly.

Finally, the 4800Ah Li-Ion battery fits nicely in one of those "Bento Box" things. What I’m talking about is those things you’re supposed to carry Gu or snacks in so you can get to them while riding. Maybe I’ll post some pictures when I get a chance.

Problems I have right now: The light dims itself if I run it too long in 1000mA. I suspect the nFlex can’t run at 1000mA for very long and it self limits. 750mA is pretty dang bright, but I’m still going to explore how to get it to run full blast.

Long story short, it was a fun project. It was funny to hear the "wow’s" from folks at the ride when I turned it on. Though I spent more on my first one so I could play with options, I think I could build one for about $125. This light is easily bright enough to actually see where you’re going – a rare or expensive thing in modern for-sale lighting systems. Go build one!

PS – I’m eyeballing that MC-E project that Allen is working on. Light building is a little bit addicting!

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