Project Headlight

Well as promised, here is my first post on my new project; Project Headlight.

With the speeds that I go at, I feel the need for a better headlight. Especially during the last couple of km before I get home at night. It is virtually pitch black, downhill (AKA quick) and there are people walking on the bike path, including those with dogs off lead. My current headlight gives me about 10 metres of very feeble light. Some quick calculations tell me that at 35 kph I am going about 9.72 metres/second, so my current headlight gives me about 1 second to react to anything on the path. I need something better.

From the beginning of this project I wanted to make myself a decent headlight. To buy these cost ~$300 for something decent. Surely I could make something almost as good for a fraction of the cost. My research led (no pun intended) to believe that Luxeon Star LEDs were the way to go (I have since learned that these are being dropped in favour of CREE LEDs). These deliver about 100 lumens of light (a 100 watt incandescent light is about 1,700 lumens). I looked around for people who had documented their projects and this is what I found:

1. This one is pretty good, but a bit bodgy.
2. This one is good but complicated looking
3. This one is also a little complicated, but seriously impressive

I decided to go for design number 3 due to the addition of the lens on the front amplifying the number of lumens to 500. It was also featured in Silicon Chip magazine along with the driver kit it employs. You can't just hook a LED up to a battery if you want it to last. It needs some sort of current limiting device. This is because a LED is a diode and a diode is just a component that lets current flow in one direction and not the other. If you overdrive your LED it will melt. You can simply put a resistor in line to limit the current, but the resistor I would need for this 5W LED would be a 10W resistor, which would then bleed twice the power I am using for light to heat. This driver kit supplies a constant current so will give me the 5,000+ hours of life the data sheet on the LED reckons it should get. It will also drop down the current from my battery to the voltage required by the LED serving a dual purpose.

Off to start looking for materials. I was lucky enough to find someone in Canberra selling off two 5W Luxeon Stars (Jaycar has now discontinued these. Probably due to the $69 RRP price tag) and two collimators (reflecting housings) on eBay which I won for $48. Bring in my friend Peter who has a Phd in Electronic Engineering (robotics) to build the switch mode power supply driver kit for me. He modified this to run at the ~40V supplied by my main battery instead of the normal 12V it expects.

I now have all the major components and need to build mount and test the light. Here are some photos:

All hooked up to my battery, ready to go


The LED mounted on a former Pentium III heatsink


The LED with the collimator on top


A close up photo of the driver board