Muscle-powered USB Charger
At shackspace we had an old manual sewing machine table sans machine standing around for years. I apparently wasn’t the first one to get the idea that “one could build a muscle powered charger” out of this, however I simply got to work on it. And lo and behold: it was done in one afternoon.
I got a bike dynamo from the bike shop across the street from shackspace. This was actually the most expensive part since it was the only thing I bought. Everything else was already there at the space.
After some prototyping I built an adapter to fit the dynamo to the sewing machine’s flywheel using some spare wood from the workshop.
The electronics is radically bare bones: no PCB used, everything is soldered together using the component’s leads and made more durable using generous globs of hot glue.
The 6 V (nominal max) AC output of the dynamo was first rectified and then buffered in a bank of 1mF capacitors. A 7805 voltage regulator without any external components is then used to convert this to a 5 V level used for USB.
Theoretically this piece of leg-muscle terrorizing equipment should provide around 500 mA of power. However, actually charging your cellphone is quite a challenge ;-) Let’s say it’s the most work-intensive 1% you’ve ever charged your phone.