[JP] was looking for a bicycle light to do some night biking around his home. He found a reasonably priced light that suited his needs, but when he started using it he found that the controller was a little lackluster. To solve some of its problems, he ended up building his own lighting controller from scratch.
The original controller’s main problem was that the it didn’t debounce the input from the single pushbutton. This meant that a single press of the button might cause it to cycle through two or three different modes, which was inconvenient and annoying. The new controller took care of this along with implementing several new brightness modes and a “strobe” mode for commuting to work to help alert other drivers of [JP]’s presence on his bicycle.
While [JP] notes that an Arduino would have been very easy to use in this situation, it wouldn’t have fit in the original enclosure. He went with an 8-pin ATtiny45, which was perfectly sized for what he needed. Everything fit together perfectly and is much more useful than the original. Maybe next he could pair it with a light that is even brighter than the one he’s currently using.
If you’re plagued by perpetually dead bike light batteries you’ll like this one. It’ll also fix the problem of remembering to turn the lights on in the first place. This hack uses an accelerometer to switch the light when the bike is in motion.
In this case the bike light was chosen for its ability to fit the control board inside the case. But with this proof-of-concept you can easily spin a tiny board with uC and accelerometer to replicate the functionality (the Bluetooth module shown above is going unused in this application). Many accelerometer chips have low-power mode that can be used to was a uC so we could easily see this having very little impact on the normally battery life of your light. The one caveat being the need to regulate the voltage as many of these lights take a 12V cell.
The other alternative is to make sure your battery is always charging during the day. This solar setup is one way, but then you won’t want to leave the thing unattended.
[Tom] sent us a link to this very professionally done project. He built a bike light that is a 540 lumen Luxeon light with a custom case. The LED, Lens, and driver were purchased first. Everything else was designed around it. The design is compact and good looking. You can download the CAD files on the site if you want to make your own. He is using an Atmel AVR ATTiny13 to control brightness.
[Matthias] sent us this project where he builds an AVR light controller. He had a halogen bike light laying around, but was unsatisfied with its lead-acid battery. He wanted to use a lithium-polymer battery but found that they can’t be used directly with halogen lamps due to their voltage. His produced 8.5 volts at full charge and can’t be discharged to below 5 volts. He new a power controller would be necessary to try to flatten that out for his lamp, which needed to stay between 6-12 volts.
He used an ATtiny45 doing PWM to change the voltage. Some other cool features he added were the high and low settings and an LED status light for warnings. You can find pictures, schematics and source code on his page as well as tons of great information. Great job [Matthias].