Tuesday, October 30, 2012

DIY bike light

What do you do when wintertime comes and you still want to ride your bike, but everytime you find some hours to spare, it is pitch black night outside? You probably need some modern, decent LED bike light, one of those that literally turn night into day. But if you don´t want to pay the exagerated sums that some companies charge for their products, or if you just like to build your own stuff, you could find it interesting to be able to build your own lights.

That´s why today, I want to show you one of my older do-it-yourself LED bike lights.
There´s more to come ...

Usually, the housing for your light and the battery are the more complicated parts to keep in mind. That´s because they are either not easy to find or not available cheap, or worse, both. Even if you really keep it low-budget, housing and batteries are still the most expensive parts of your build if you are looking for something with a decent quality.

That´s why for my first DIY light, I wanted to use some parts that I had already lying around.
I used an old Mini MagLite Torch, or to be precise some cheap copy. After measuring the head of the torch, I found it could be used to fit a small 25mm (one inch) LED star. I chose to use one with 3 CREE XPG LEDs, quite a bit of power for a small light.

First of all, the torch was cut into several pieces. The good thing about this type of torch is that the head screws into place, which gives you the possibility to use the upper part of the handle and screw it into the light head bottom up in order to have a plain surface to mount the LED star. Otherwise, the head would just be hollow and the LED star would not have enough contact with the surface of the light head to dissipate the heat.

Because space inside the light head is really tight, I needed a very small driver. I ended up using a
┬ÁBuck-Driver with 1000mA current from PCB Components. The rest of the build consists of some CARCLO 3Up optics well suited for the XPG LEDs and some silicon wire.

Did I mention space was an issue? The part of the former handle that I used inside the head has barely enough inside diameter to fit the driver, but after some fiddling and then some more, I managed to squeeze it all into the head. On the following picture you can see the part of the handle that screws into the light head:

The zip-tie serves as a very basic strain relief and sits against the back of the housing.
The original retaining bezel on top of the light head that usually holds the front lens of the torch in place luckily was just big enough to put it over the broader part of the optics, so that the rest of the housing could be assembled.

Once everything was finally done, I went out to test the light. The good news was that the power of the three LEDs is definitely enough for all biking purposes, even if you are out riding difficult trails at night.
What I did not fully understand before the light was ready, is how much heat the three high-power LEDs produce. That was the bad news - the housing was simply too small, or to be precise, had not enough cooling surface, to cope with the heat of the LEDs. The light became so hot that you could not hold it in your hands for longer than one minute!

That´s why, even if the build went well, I decided not to use the light in this form and transfered the parts to one of the easy2led housings.

More about these housings and other builds in one of the next posts.
If you are looking for more information regarding DIY bike lights, check out the following links:

mtbr.com - DIY lights
IBC - Elektronik rund ums Bike