I've posted before about a particular problem I have: my phone runs out of battery power after a few hours of GPS usage. Even when I don't use GPS, I tend to take quite a few pictures when I'm out and about.
There are well-known solutions to this problem. Simply by replacing the front wheel on my bike with one that contains a hub dynamo, then add something like a Ree-charge device. Following this, it is simply a case of plugging your USB device and pedalling off into the distance. Except...
Except for the cost! A fully-built wheel containing a hub dynamo costs around £110, with a Ree-charge coming in at an additional £90. Two hundred Pound simply to keep my phone charged up seems a tad steep!
And then I stumbled across an article online that mentions converting a Nokia DC-14.
The Nokia DC-14 is Nokia's bicycle charger kit, and it contains an old-fashioned bottle dynamo, as well as some circuitry to convert the current from AC to DC, and to regulate it. Finally, it contains a handlebar mount that holds the rectifier unit and the phone securely, all for only £25-00!
Now this unit was made by Nokia, and designed to only charge their phones, so it comer with the proprietary 2mm Nokia adapter. I snipped this Nokia connector off, then added a normal micro-USB connector in its place.
The actual wiring was really easy: On the Nokia side, there are two wires: red and white. On the micro-USB side, ignore all except the red and black wires, then join the red wires from each side together before joining the black and white wires together.
End result: I have power! Old-fashioned, perhaps, but power none the less.
Cycling with the dynamo engaged adds a noise somewhat like the wind whistling past your ears, but on the limited trials I've had so far doesn't seem to add any noticeable drag. Obviously at least some pedalling effort must be absorbed by the dynamo, and a longer trip - particularly one where the bike is laden - will certainly let me know how much harder it'd be.
There are different opinions on bottle dynamos, with some claiming it will wear out a tyre's sidewall within a week. I have found many others saying a bottle dynamo only wears out a sidewall when it is incorrectly mounted. Time will tell in my case, although I believe it has been properly mounted.
There are however a few glitches still: my phone interferes with my wireless cycle computer, with the end result being my cycle computer sometimes showing I'm doing speeds of over 55 mph, when in fact I'm hadly moving! I will have to see what I can do to re-position the cycle computer, although obviously there are limits to how far I can move it along the handle bars! In a worst-case scenario I may have to only use a wired computer, which isn't quite the end of the world.