new hw project: dynamo gadget charger

[Panagiotis Palias]

Hello all,
I recently got myself a functioning bicycle. To my frustration the mobile phones now-days are very much power consuming if you have GPS turned on to track the route you follow, while listening to some music over the bluetooth headset.
So I had the idea to make a mobile phone (or whatever gadget you have) charger from a regular bicycle dynamo. I discussed it yesterday with Martin and he is interested too. We found some dynamos in the storage room with the bicycles. They produce 6V AC and claim 3Watt of power, which should be enough as it gives 0,5A.
First problem is to regulate the current from AC to DC and second problem is to make sure the system provides charging power in a continuous way, so that the phone will not go into "charging - not charging" loops whenever the speed decreases. Today is a bicycle repair workshop at base48 so I'll drop by to discuss it with someone else who might be interested. Hope Martin will make it too :)
Have a good day!

[Juraj G.]

hi, first thing i think of is to use diode bridge to get pulses of one polarity,
unfortunately, you'll loose some voltage from dynamo right on this stage
http://en.wikipedia.org/wiki/Diode_bridge

2. charge a capacitor with those pulses

3. convert up the voltage on capacitor so it has constant voltage,
there are circuits
that are used to drive power LEDs with single 1.2 - 1.5V cell
this solves problem with slow ride on bike and low voltage from dynamo
there is a loss of efficiency on this stage

4. charge a new battery that will belong to charger circuit
this solves continuous charging of mobile phone and you can store
energy from ride
while not charging.
battery should not have RAM effect so it can be charged/discharged at any state
some considerable amount of energy is lost during charging of battery

5. connect a charger circuit / mobile phone to charged battery, or make
a switch that will detect if there is enough voltage to connect a mobile
phone

Dňa 11. apríla 2012 14:30, Panagiotis Palias <pana...@gmail.com> napísal/a:

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[Martin Janovský]

Will be there too!

M.

Dne 11.4.2012 14:30, Panagiotis Palias napsal(a):