MAKE Flickr photo pool memeber Trialex posted this little (battery free) USB power LED torch, here’s how to make your own… -
A rechargeable, battery-free LED torch which gets it’s power from USB and stores it in a capacitor.
I reckon USB stuff is cool. I also reckon LED stuff is cool. I HATE paying for batteries. I love my shaky torch. Putting all this together, I thought I’d make a LED torch, simmilar in form to those keychain types, which stores it’s power in a capacitor. The capacitor is charged from the USB port.
This is only a “proof of concept”, and is intended to show it works. I doubt it will have the best performace, but that’s not the point. I think I should be able to do it fairly cheaply, for about the cost of a keychain coin-cell LED light - Link.