cuts off everything above 5.1V. I wired the output to
a female USB connector to let me connect the iPod
with its included USB charging cable.
For a detachable enclosure — so I could remove
the system from my bike while it was parked —
I considered an Altoids tin. Those are hard to find
here, but I did have a couple of old Apple mice,
so I decided to use a mouse case. I found that an
S-video female connector fits perfectly onto an
ADB (Apple Desktop Bus) connector, so I left the
mouse’s cable intact. Inside the case, I wired up
the hand-crank charger’s PCB and battery along
with my voltage regulator and the USB port for the
iPod. The charger also had a neat little charging
light, which found its way onto the back end of
On my bike, I connected the dynamo to an
S-video plug that hangs from my handlebars. That’s
where I connect my mouse unit, and then I plug the
iPod into the other end of the mouse. Both iPod and
mouse charger are kept protected by iPod socks,
one of which I embroidered with a skull design.
Then I started thinking that it would be silly to
have a working dynamo on my bike but no lights,
and even sillier to run LED lights with batteries
while riding with the dynamo on. I did some voltage
probe experimenting with an identical hand-crank
flashlight, and found that when you switch the light
on while cranking, it stops supplying voltage to the
charging jack, and when you switch the light back
off, charging resumes. This meant that my charger
could easily work the same way.
I opened the charger mouse back up and connected two more wires from the ADB cable to the
contacts for the flashlight charger’s light. On the
other side, I split these contacts into two pairs that
supplied front and rear LEDs for my bike, which fit
where the original bulbs had been.
Finally, I wired the mouse button to the contacts
for the flashlight charger’s light switch. So the
mouse button has one function: switch between
turning on the bike light and charging the iPod. In
theory, you could run into trouble at night, with no
more music and a long way from home. But during
the one and a half years I’ve been using my charger,
this has never happened.
Mark Hoekstra has a passion for technology and the urge
to control and combine whatever he lays his hands on.
This results in some original projects you can see at
Fig. A: Bike-powered iPod
charger detaches easily for
parking. Fig. B: Original 6V
hand-cranked charger with
voltage stepped down to
5V for USB. Fig. C: Mouse
case contains charger
electronics and connects
to bike dynamo via S-video
plug on handlebars.
Fig. D: iPod, opened-up
charger, and iPod socks.
Fig. E: Charger electronics,
battery, voltage regula-
tor, and USB port packed
inside mouse case.