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Ridiculously bright keychain rechargeable flashlight / flash driveAll > Tech > Inventions > Ridiculously bright keychain rechargeable flashlight / flash drive by natetrue
I happened to have a spare tiny USB flash drive around, so how better to get USB power than to also be a flash drive? That way it has a double use on the keychain.
I decided to go with the MAX1555 lithium-ion charging IC (same one from the binary watch project), and an 80 mAh lithium-polymer battery from All-battery. The battery has about the same size as the rectangular USB connector and so works well for this project. It also includes a protection PCB pre-connected to it (if you choose that option when you buy it) so that if I make any crazy mistakes it won't explode the battery. Convenient, eh?
I used a 10 ohm resistor in series with the light module to limit the current to about 80 mA, which is the maximum peak discharge current rated for the battery. Since it's activated by a momentary pushbutton we don't have to worry about the rated 16mA continuous discharge current limit.
Also note that the flash drive fits almost completely in the metal USB connector and so doesn't take much extra room. The charger chip is also in the metal part and is protected with electrical tape as well.
I decided to go with a full-epoxy casing because it's easy to make and sculpt, and because it will rigidly hold all the parts exactly in place, firming up any possible loose connections and filling gaps to keep wires from touching what they shouldn't.
The battery should give a little over an hour of light and the Li-poly chemistry has a very low self-discharge rate so it should never have to be intentionally recharged if used regularly as a flash drive (it takes about an hour to recharge from USB if fully discharged first).
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