AVR Light Controller


[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].

12 thoughts on “AVR Light Controller

  1. nice. You have to watch with Li Ion and NiMH packs that you don’t over discharge them. Did a similar project using a PIC, NiMH and an High power LED running at 9 watts for a bike light of my own. Damn thing will shoot a beam 300 yards.

  2. This just reminds me of an awesome flashlight idea i had the other week… Basically get a flat grid of 3 or even 5 watt LEDs, like the Luxeon Star series, maybe 3″x5″, stick a slim Li-Po battery in it, and keep as much charging hardware as possible in a separate charger so the housing stays small. The damn thing would be super thin, but put out a blinding amount of light. Granted the battery life would be crap, so you would need to keep it charged all the time, but it would be impressive to see something so small put out so much light, even for a few minutes. The key thing is that Li-Po’s are thin and can source lots of current.


  3. nice project.

    If you are unsure of your skills, you can spend about $10 and get a protection PCB module. Over/under voltage and over current protection. Or if you buy individual 18650 cells, some of them are stacked onto the cell (they vary from simple PTC, to full protection).

    @taylor: I guess the only problem would be duty cycle, like you said, but for another reason: it will heat up quite quickly.

  4. Hello there,

    This is off subject but today 1st page has link to next page below and next page below only has previos page only which lead to 1St page (no next page link on the secong page)


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