Bicycle

iPod Charger

A sidewall dynamo powers both lights and tuneage. By Mark Hoekstra

After buying an iPod mini a couple of years ago, I started experimenting with ways of extending its battery life. First I tried the Perfectmate hand-cranked flashlight/charger, only to find out that it takes up to 20 minutes of cranking to generate just enough power to boot the device. As well as making me appreciate how much power today’s lithium-ion batteries can hold, this got me thinking about other ways to human-power my iPod.

I LIVE IN HOLLAND, WHERE BICYCLES ARE

one of the most popular means of transport.

A typical Dutch bike has the old lighting system, which consists of front and rear light bulbs powered by a 6V dynamo that runs off a friction wheel on the front tire. So I got the idea to open up the flashlight charger, find out where the dynamo connects to the PCB, and connect my bike dynamo there.

The iPod mini takes USB-standard 5V and can

80 Make: Volume 11

A

handle up to 6V. The hand-crank charger nominally supplies 6V or a little more. Its battery pack stabilizes the current it produces, but there’s no regulator to limit its output voltage. So I needed to add something to prevent the charger from possibly damaging the iPod with excess power. I first thought of a voltage regulator IC like an LM7805, but these are designed to step power back from much higher levels. Instead, I simply used a Zener diode, which

Photography by Mark Hoekstra