Calling all electrical engineers, cyclists and gadget freaks: How can I modify my SON dynamo bicycle wheel hub so that I can use it to power a variety of peripheral devices (cell phone, iPod, GPS, etc.)?
I am a randonneur. I ride my bicycle very long distances (this year I plan to complete the Paris-Brest-Paris
, a 1200km event held once every four years in France in August). And I get very bored sometimes. I carry a cell phone with me for emergencies, a tiny digital camera, as well as an iPod full of audio books and music that help me get through the long miles. I also would like to add a GPS-enabled Mobile PC device/Blackberry. Ideally, I would like to live-blog the ride, with text, audio, and photos from along the route, without having to carry a ton of spare batteries. Most of the devices are rechargeable, but recharging them would require stopping long enough to plug them in to an outlet, somewhat counter to the notion of staying motion. We are talking 90 hours on a bike here, so the ten or so hours you'd normally get from these devices won't cut it. Carrying extra batteries is not an option either since most devices have their own internal rechargeable batteries.
The front hub on my bicycle is a SON dynamo hub
. These hubs are traditionally used to power a headlight so that randonneurs can ride at night without having to rely on battery powered lights. The hubs generate approximately 6V of current when spinning, and have two outputs: one for the main headlight and one for an optional second light.
My question is this: is it possible to somehow use the second output to serve as a power source for peripheral devices of varying voltages? How would this be achieved? Are there off-the-shelf parts available for use in putting such a system together? Is a 6V dynamo sufficient to power most devices (ie, my Powerbook input is 24.5V, so powering something as big as a laptop is out, right?) I am assuming it would require an intermediate energy storage device (ie, a specialized battery) to go between the device and the dynamo (since the current is not present when the bike is at rest), but what about the varying voltages of all the separate devices (anywhere from 1.5 V to 5.5V, not to mention all of the different connector types).
I did find a system called the GeoBici
that makes reference to a specialized alternator used to power an iPaq Pocket PC with GPS, but no specifics were given, nor can one purchase said system.
Other issues: a lot of extra weight and overall bulkiness would make this not fun. I also don't want to jeopardize the function of the headlight, which is actually the most important part of this whole system.
Finally, I can tell you that there are hundreds, perhaps thousands of users of SON hubs who would like to see products developed along this line, so all you entrepreneurs out there might want to get a'crackin'.