Bike Light Build: Part One

Just a few quick note about my latest project. I'm hoping to actually document this one in a useful manner, so bear with me. I've done a little bit of research about DIY lights for mountain biking and finally decided to get around to making one. Fall is upon us and soon there will be little to no chance that we will see the sun for months on end. I will therefor need something to light my path while biking.

I had considered going the cheap route of using a halogen light, but the run time is abysmal compared to other options, such as LED and HID. HID is simply stupid expensive, so I decided to go with an LED. After reading a website all about such lights here, I decided to go with a Cree MC-E emitter from ledsupply.com. The MC-E is actually four emitters closely packed together under one lens and it comes pre-mounted on an aluminum plate to help dissipate heat. The emitters are wired in series which means the forward voltages must be added together, resulting in a Vf of 12.8-13.2. The current is shared by the emitters and I will supply that with a Luxdrive Buckpuck with which I can provide a regulated 500 mA. I chose the wired model, with the potentiometer to vary the current from 0-100%.

To test the Buckpuck and LED I soldered some speaker wires that I scrounged from a box of stereo stuff I had in the closet. I put some alligator clips on those to aid in testing as well. I wired the Buckpuck to my regulated power supply and set the PS to 14.4V which is the voltage that I can get from two 7.2V Ni-Cd battery packs that I bought for my remote control car, when they are wired in series. I then attached the clips on the LED to the Buckpuck outputs and turned on the PS. Voila! Blinding frigging light. Seriously, don't look directly at this thing. At 350 mA this LED throws approximately 430 Lumens and I was driving it at 500 mA which should give it a 30% increase in flux. That is truly bright. I didn't leave the light on for long as it was not attached to any heat sinks and even an LED will heat up when driven at 6.5 watts. I just wanted to verify that everything worked anyway.

Next step... check to see how low a voltage this thing can be driven at so that I can be sure that the battery packs I have will work even when low, or if I need something with more than a nominal 14.4V.