White Wire Light System

Ever since I built my motorized bike 2 years ago I have experimented with LED based light systems powered soley by the white wire and without batteries. I tried half wave rectification of the positive as well as the negative half cycles from the generator but ultimately settled on a full wave bridge. One thing I discovered was the usable output voltage ranges from about 25VDC down to about 8VDC depending upon the electrical load. The generator can source 3-4 watts which is adequate for a decent LED light system. The key is to efficiently convert the relatively high output voltage down to the 3 volt range for a high brightness white LED. As others on this forum have noted, the best way is to use a stepdown or buck DC-DC converter. This is what I did for driving the head light. I also included a tail light and side lights to make my bike more visible. I connected 4 red LEDs for the taillight, 2 red and 2 white LEDs for the side lights all in series and power them directly from the output of the generator. The attached photos show the results. The beam pattern on the garage door is from about 20 feeet down my driveway.

I bought the head light and tail light on eBay. Chinese package that included both. I gutted the tail light and use only the enclosure to house 4 high brighness red LEDs. They came from a trailer hitch brake light I found at Harbor Freight. The side red LEDs are from Radio Shack and the white side LEDs are from a 6 LED flashlight I took apart. The head light is advertised as 5 Watt but that is pretty optimistic. I drive it with 500 mA @ ~3.4 volts. I mounted the headlight with a couple of pipe straps bent into a "U" shape.

Rockenstein - yes, that is the schematic of my lighting setup. It has evovlved from a pretty basic buck voltage regulator to something a lot more complicated than I had intended. I just kept finding ways to improve the performance but each iteration seemed to require adding more circuitry.

I am working on another design that should replicate all the features of this one but will be a lot simpler at least in terms of parts count. I hope that it will be something that anyone with good mechanical skills and some basic soldering skill will be able to build. I think that most of the motorized bicycle builders out there have those abilities. I will post the results (good or bad) when I finish building and testing it. Some warmer and drier weather in Seattle would help.