Dynamo Charger for mobile phone

[spartan]

Hi, Anyone know how to modify a normal bicycle dynamo so that it will charge my mobile while I'm on the road. :idea: I have seen the wind up chargers, but that's not what I'm after. Would I need to add a circuit to the output of the dynamo to change to DC, or will it be okay if I just cut the jack from a normal mains charger and connect it upto dynamo.

Any suggestions or links to websites that can help greatly appreciated.

 

[Russlk]

Your dynamo is no doubt a permanent magnet AC generator, designed to drive a 6 or 12 volt lamp. Which is it, 6 or 12 volts? At any rate, your 230 volt charger is not going to work. With no load, the dynamo could put out 25 to 50 volts, so the charger has to work with that. What are the voltage and current requirements of the device that you want to charge?

 

[Exo]

First of all you'll have to figure out the voltage your normal charger outputs.

Is it an adaptor that was supplied with your phone? if so, take a look at it, the output voltage should be listed, otherwise you'll have to measure it.

Then you'll have to measure the output voltage of your dynamo (ac) And see if it outputs more, or at least the same as the adaptor. If this is the case then you could probabely just rectify and regulate your dynamo's output and connect it to the phone.

 

[spartan]

I'm hoping to use a 6v/3w dynamo which should be fine as far as output goes as the phone requires only 3.5-4v to charge with about 350mA. It's the rectifying/smoothing circuit I might need to put on there that I'm not sure about. I'm not using any part of a mains charger, other than the jack whcih I will cut off and connect to the dynamo/smoothing circuit. Cheers for any help, most appreciative...Spartan.

 

[jem]

First of all, you need to determine that type of battery the cell phone uses. The charging algorithm varies depending on the type of battery. Most modern cell phones use a single LiIon battery (cell plus protection circuit). They require current-limited, constant voltage (4.2V) charging, with cut-off (charge termination current around 50mA or so). Check out the LT1734 from Linear Tech. It is easy to use, and has an undervoltage lockout feature as well.