techno whiz cyclist

[ross_burkin]

I stumbled across this page while looking for phone charger for that works of a bicycle dynamo. Does anyone know of such a thing?

http://geektechnique.org/projectlab/511

[Banshee Ambulance]

Ross, If your phone is USB compliant then it should be relatively easy to do providing that your dynamo kicks out enough voltage. Then you would need to connect a 5V regulator. Also, remember to short the data lines together with 100 ohms (I think) to tell the phone it can draw poser for charging. That is why it takes forever to charge stuff from the usb port on your computer.

[Phil Alderson]

The dynamo's that you get for bike lights generage AC, so at varying voltage and frequency. You would need to build a rectifier to convert that to DC.
To be on the safe side I would look for a battery powered phone charger, then rig a system to charge the batteries of the phone charger. This puts your expensive phone one more step away from the variable voltages from the dynamo.

[roland_trim]

That guy is also dutch. He therefore has zero concept of hills!

[Banshee Ambulance]

The dynamo's that you get for bike lights generage AC, so at varying voltage and frequency. You would need to build a rectifier to convert that to DC.
To be on the safe side I would look for a battery powered phone charger, then rig a system to charge the batteries of the phone charger. This puts your expensive phone one more step away from the variable voltages from the dynamo.

A true dynamo will generate DC!

Assuming you have a true dynamo then I would use a zener diode rather than the regulator. A regulators function is to always give a constant voltage output regardless of current load and requires a higher supply voltage (7-8V for a 7805 at a guess). A zener diode will just prevent over voltage supply. A quick look at the ipod charger you posted suggests he did the same thing. Add some beefy capacitors, a couple of resistors and some protection diodes and I cant see any reason why it would not work assuming you can pedal fast enough! Remeber that for DC to reduce voltage you can series diodes together as a rough and ready fix, each diode will drop around 0.7 volts. Let me know how it goes.   

[Will_Lee]

Bike dynamos are really alternators, for the same reason cars once had dynamos but now universally have alternators: You get a lot more juice out of an alternator due to no switching losses.

[Banshee Ambulance]

If you do have an alternator then that is an easy fix with a full wave rectifier and smoothing capacitor. Remember that the output voltage once converted to Dc will be 1.41 x rms ac output voltage - diode losses. In the case of a 6V alternator this would mean an appox output voltage of 8V.

Alternatively, something like this may work! 

http://www.fuddymuckers.co.uk/gallery/electrics/circuit_diagram.png

[Phil Alderson]

This might be what you were after:

http://www.wired.com/gadgetlab/2010/06/nokia-announces-bike-powered-phone-charger/