DIY bike light for on-road use.

[spasticteapot]

I'd like to build a bike light for under $40 that will produce plenty of light for night commuting but won't dazzle anyone in front of me. I was thinking of using a buckpuck variable driver and a single LED with a narrow reflector.

Any suggestions?

 

[KentS]

A one-LED version of what I made would be under $40:

http://www.candlepowerforums.com/vb/showthread.php?t=222622

I use a light-bulb housing from DX, a Lumiled buckpuck 1000mA from Cutter with a potentiometer. I drive it with 4 18650 TrustFire batteries in a holder and pouch from Turboferret
http://www.turboferret.co.uk/
You can make a much cheaper battery pack with standard 1.2V AA rechargeable and battery holders. I think the buckpuck wants something like 2V over the forward voltage of the LED to work, so 6xAA will do fine. I've changed the potentiometer to a more sturdy one as the one supplied by Cutter was very fragile. I have one +/- 10 degree lens and one +/-20 and that works great. With only one lens I would go somewhere in between +/- 12 or 15 degrees.

 

[yellow]

get Yourself a Fenix LD20 + traffic cone
cut away some of the front part of the cone to get a main beam enough for You + remaining cone to be visible form the sides and cutting away spill that would disturb others.

for the overall price You can not build a homemade light in comparable quality
(+ You have a nice small flashlight with actual technology also)

 

[spasticteapot]

get Yourself a Fenix LD20 + traffic cone

Traffic cone? You want me to mount a traffic cone on drop bars? All the flashlights you list are too expensive, too long, and too short-lived for use as a bike light.

A one-LED version of what I made would be under $40:

http://www.candlepowerforums.com/vb/showthread.php?t=222622

That looks terrific!

I'm curious, though - why not get a 1000MA buckpuck and use the dimmer function? You'd have the same net result, but you could crank up the output in case of heavy snow.

 

[KentS]

Sorry if I was unclear. I have built in a buckpuck into one of the plastic furniture feet. With the potentiometer I can adjust the current from max 1000mA all the way down to 0mA on the fly. The new potentiometer I use is a bit bigger so it is easier to operate with thick gloves on. (I really wouldn't recomment the potentiometer supplied by cutter).
This is the buckpuck:

http://www.cutter.com.au/proddetail.php?prod=cut131

With two series emitters like I have it costs more than $40 to build but really a P3D (my previous bike light) does not compare. I would rate the output of my light somewhere around 450 lumens at 1000mA with a much better beam profile than the Fenix. The Fenix lasts 1h on turbo with AW rechageables. This light shines almost 4 hours on full blast with 4x18650 2500mAh TrustFires.

 

[sfCyclotourist]

This was really cheap to put together ($30-40 max), easy to build, and works great:

http://yojimg.net/bike/equipment/lights/led_lights.php#singlecree

The angled shape of the housing provides a decent horizontal beam cutoff and overall useful beam shape.