Matchstick- mini infinite flashlight

thingiverse

I made a mini hand-cranked flashlight as a gift, but it could be very useful in emergencies too. With just a few turns of the generator knob, you can get a couple of minutes of light. It has a mini generator, a joule thief, a 5mm white LED, a full bridge rectifier, and a super capacitor. You will also need some super glue or epoxy glue. Overall, it shouldn't cost more than $5-10, and you might be able to salvage some parts from old electronics. A schematic is posted with the pictures. You do need some soldering skills to make this project. I designed the whole circuit in my head, but if this becomes popular, I could also create a PCB and sell it. I'm posting some pictures that show how I assembled it. There are two versions of knobs - one uses a metal insert from a modified cable connector, while the other one fits directly onto the motor. I suggest you heat up the shaft of the generator with a lighter and then slip on the knob for a better fit. Here is the parts list: * A 220uH inductor (I didn't have one available when I made mine, so I used two 100uH inductors in series) * A 5252F garden light chip (this will be the heart of the joule thief) * A 1F 2.7V super capacitor (you could use a higher capacity, but this one is small enough to fit into the housing and requires only a few turns of the generator) * An SMD full bridge rectifier (you can also make your own with four diodes - I salvaged mine from an old phone charger. It's not a critical component, so you can use whatever you find) * A 30RPM geared micro motor that runs on 6V (find it on eBay) * A 5mm white LED You can use a motor with a higher RPM reduction (around 60 RPM) if you want - it will give you less power per turn, but it will last longer mechanically and be more reliable. For the first time after soldering everything together, I needed to "kickstart" the capacitor with an external power source (I used a battery). But after that first lighting up, it has been working perfectly on its own generator, and you can glue it shut. I'm not sure why this happened - maybe it has something to do with the chemistry of the capacitor. If anyone knows, please leave a comment below.