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There are a lot of mini-maglite hacks out there where people replace the bulb with a white LED. The only drawback is that white LEDs run on 3.3 volts, and 2 AAs only give 3 volts so the white LED runs dim. AntonOlson solved this problem by building a DC/DC converter in the shape of a AA battery that boosts a single battery to just about 3.3V, both of which go into the mini-maglight. - Link.
Battery shaped DC-DC switcher in a maglite
Posted by Phillip Torrone |
May 16, 2006 02:11 AM
DIY Projects, Electronics |
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So, like... what kind of battery life tradeoff are we talking here?
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i'm not really sure how much battery life the flash light would usually get with the bulb (seems like 10 hours, and eventually the bulb dies) but with this set up... maybe 45-50 hours with a duracell. here comes the math...
1 x AA = 1.5V * 4000mAh = 6000mWh
1 x white LED = 3.3V * 30 mA = 100mW
so...assuming that the converter runs at 80% efficiency, 6000mWh -> 4800mWh (converted). 4800 mWh / 100mW = 48 hours
on a rechargable it would be about half that...
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An arguably simpler DC/DC converter for this application is the Joule Thief, previously highlighted on the makezine blog.
I've built a bunch of these-- they're really tiny, and can drive a white LED off of a single 1.2 V nimh cell. They're not as efficient as a well-tuned DC/DC, but they are dirt cheap and shockingly easy. After the first one, you don't even need to look at your circuit diagram. =)
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