Mini hand cranked flashlight i maked as a present, but it could be quite handy in emergencies. With few turns of a generator knob, you can achieve couple of minutes of light.
It contains mini generator, joule thief, 5mm white led, full bridge rectifier and super capacitor. It also need bit of super glue or epoxy glue. All in all, it should not cost more than 5-10$, and some stuff you can salvage from old electronics. Schematic is posted among pictures
It require some soldering skills. I created whole circuit "in air" but, if it become popular, i could also make pcb and sell it.
Im posting couple of pictures with details how i assembled it. There are 2 versions of knobs, one use metal insert from modified cable connector, other one goes directly onto motor. I suggest you heat up shaft of generator with lighter and then slip on knob, for better fit.
220Uh inductor (i didnt had one at hand when i maked mine, so i used 2x100uh in series)
5252f garden light chip (this will be heart of joule thief)
1F 2,7v super capacitor (you could use higher capacity, but this one is small enough to fit into housing, and it requires only few turns of generator)
SMD full bridge recitifier (you can also make your own with 4 diodes, i salvaged mine from some old phone charger. Its not critical component, so you can use pretty much any you find)
30RPM geared micro motor 6v (find it on ebay)
5mm white LED
**You can use motor with higher rpm reduction (~60 rpm), it will give you less power per turn, but it will last much longer mechanically and be much more relaible
***For first time running after soldering everything toghether, i needed to "kickstart" capacitor with external power source (you can use battery, i used bench power supply), but after that first ligtning up, its working perfectly only on generator, and you can glue it closed. Not sure why that happened, i guess it have something to do with chemistry of capacitor. If someone knows, leave comment bellow