I have been searching for a solution to run small USB chargable devices powered by the dynamo hub of my Surly big dummy bicycle without additional batteries. I was not willing to design a circuit myself and I do not like to blow up the connected device due to unsufficient voltage protection. There are several converters available for charging USB devices as like music players, phones, PDAs or navigation devices on the bicycle. I got me the
bike charger from a German distributor and installed it today.
In my blog there are some pictures of initial cabling. I still need to attach the PNA to the handlebar (still waiting for some parts) to be able to complete the installation. Basically it appeared to work, when connecting the charger and spinning the wheel. The device should be virtually sufficient to power any USB charged device according to USB spec (5V DC constantly, 500mA at max, even at low speed). The box has got 50g approximately and is quite small, but must not be exposed to rain or humidity. According to manufacturer it will not heat up due to the digital design of the circuit. I am a novice with electronics, so I cannot tell any details, but I will be using it for some bicycle touring within the next time.