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Hand crank LED flashlight hacked - now also USB charger

last photo ←

Here in Russia people sell stuff on the commuter trains. So I once bought this really cheap hand cranked flashlight for 100 rubles (~$3 US). It worked just fine. I had to take it apart. Inside there were two 3 volts batteries in series, meaning that the dynamo inside the unit generated about 6 vdc. I immediately soldered a usb cable and made this into a hand crank charger for my Android phone.

Here are some pictures of flashlight being taken apart and a USB connector being soldered to it. To figure out polarity and how to propperly connect the usb line I read this page: http://pinouts.ru/Slots/USB_pinout.shtml

I then tested the unit and took this video:

3 comments

Aug 13, 2011. 10:08 PM

Winged Fist says:

What a great idea!
I'll have to try this when I come across a hand crank flashlight...
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Aug 14, 2011. 1:10 AM

pashanoid (author) says:

Do check the voltage, though. Good luck!

Aug 22, 2011. 12:36 PM

CementTruck says:

Yeah, my thoughts exactly. You don't want more than a 5V output, which is the ubiquitous USB output voltage. I'd hate for you to damage your phone, or other expensive product.

http://www.hardwarebook.info/Universal_Serial_Bus_%28USB%29

You'll need a voltage regulator. Try googling it or even searching instructables. I think I've seen some floating around the site.

Try hooking up a meter to the output and crank as fast as you can and see what the readout is. If it never gets higher than 5V then you'll probably be safe without the regulator.