I recently completed building an LED headlight for my bike. It's taken months of designing, redesigning, stalling, discouragement and discovery, but I finally finished.

It started out a couple of years ago when I was directed to the Action Light - a caving light made with bright white LEDs.

A year or so later, and with no small amount of help from colleagues at work and my brother-in-law, I decided to make a bike light. The fact that my Cateye headlight was so woefully inadequate helped spur my interest, and I didn't finish my light until the Cateye finally fell apart.

Anyway, I won't bore you with too many details at this point. I'd rather show some pictures. (Apologies for the blurry pictures - my digital camera isn't very hi-res)

This is where all the experimentation with circuits took place. This one was taken in the later stages of development - note the circuit boards to the right. (I ultimately had to redesign and make some new boards)

IT LIVES!

Here it is installed in the APS film cannister I used as a casing. The battery holder is a temporary setup.

This is the complete setup, including the charger kit I got from Dick Smith Electronics to charge the 6 AA NiMh batteries I'm using.

Here it is installed on the bike showing where the battery goes. Now you see it...

... now you don't.

First backyard test. This was before I discovered the overheating problem which was sapping brightness from the LEDs which eventually required me to make whole new circuit boards.

Everything works fine now. This was taken on the second real use of the light. I find myself seeking out the darkest roads I can find these days. It's a pity that with summer approaching I don't get to ride in the dark very often.

This is a particularly dim section of Lytton Road. First with the light off...

... then on. This photo doesn't really do justice to the light quality of the unit. It lights up the entire road with an extra bright spot just where you need it in front. It was lighting up the roadside reflectors on the other side of the road from 50m+ away.

Lastly, here it is reflecting off the back wall of my shed. This gives a bit better idea of the pattern of the light output. It's bright in the centre, but doesn't drop off to nothing suddenly at the edge of the beam like typical spot pattern headlights do. This also aids other road users being able to see me from up to 90° either side.

So, we've got a bright light. So what? Why is this light any different from any other light on the market.

Well, there's a couple of things.

First, it's light. The batteries I'm using are high capacity NiMh cells, giving 1500mAh. The total weight of the unit is 220g.

Battery life: I haven't made a very accurate calculation, but I think I get about 4 hours out of it. That's in constant mode. I'm contemplating making a 6 'D' cell battery which would give me 8Ah and a proportional increase in run time. The thing is that they're expensive, not to mention heavy. If I ever do a midnight century (haha) I might do it.

That's the other feature. It's dual use. I have designed it with a flashing mode similar to commercially available 'blinkies'. In this mode I have restricted the light output relative to the potential of the LEDs, but it is still brighter than most regular blinkies, without causing a disturbing strobing effect on the road. In this mode the light will run virtually indefinitely between charges (1000 hours +).

The only downside is that it's expensive, purely because bright white LEDs are expensive (I paid over AUS$7 each for mine - I'm using 10). I expect as they become more common, and they are, the price will come down, and they'll get even brighter/more efficient.

For further details, feel free to contact me.

NEW (added 01-10-02) I have finally gotten around to uploading the schematic and PCB layout I used. It's a PDF file, so ensure you have the reader before trying to open it It's pretty rudimentary, but should be sufficient information to get you started. Printing it out should give you the PCB layout in the correct scale to transfer it directly to copper. The only other trick is the switches on the schematic are actually just one double pole/double throw toggle switch (centre off) (See example here)- wire the power supply to one side and the resistors to the other. If there's sufficient interest I'll try to put together some more detailed construction information.  Enjoy

I would like to thank all the people that have contacted me regarding this light. I seem to get a few messages a week with questions regarding it, and, strangely enough, very little spam. It's all been very gratifying, and the amount of interest has certainly surprised me, so again, thank you all.

The most frequent question seems to be 'what circuit did you use?', which prompted me to upload it to my site. Hopefully that will answer many questions. If anyone actually goes ahead and builds one from the above information I would certainly like to hear from you at allistermclaren at optusnet dot com dot au.