I've looking for a way to charge my electronics while I excercise on my bike. I couldn't find dynamo powered USB charger so I decided to try and make one. I used what I could find and cobbled it together based on information from Instructable and other on-line sources.
Step 1: Installing the Dynamo
This was not complicated. I just followed the instructions that came with the dynamo. I tested the voltage coming from the dynamo and soon realized it exceeded my listed specs. The specs specified a 6 volt output but my testing confirmed not only was the voltage AC instead DC (which I expected) but the output could acheive up to 13 volts.
Step 2: Rectifying and Regulating the Voltage
I found an Instructable explaining the creation of a Rectifying Bridge using common diodes. A clear example is also available on Wikipedia here. http://en.wikipedia.org/wiki/Diode_bridge So I built my rectifying bridge and testing it. It worked as described.
I then had to regulate the voltage and amperage to an USB standard rate of 5.5vdc and 500Ma. I found it easier to recycle a car lighter USB device to do the work for me rather that building something. Safer for everyone involved. :)
The output for the car lighter USB device says it should be 5.5vdc and 700Ma but testing both in the car and on the bike showed 5.5vdc and 950Ma. Since I've used this device a lot in the car, I'm accepting these figures as safe and fine. If you think otherwise, please let me know.
Step 3: View the Video
I tried posting this video to Intructables.com but it is too big so it's on Youtube.com
Please feel free to comment. I'd be interested in what you might have to say about my project.
Cheers and Thanks!