Charge Mobile (5V USB) Phone/GPS or Other Equipment From Bicycle Dynamo - 3 Euro - 5 Elements Only :)




Introduction: Charge Mobile (5V USB) Phone/GPS or Other Equipment From Bicycle Dynamo - 3 Euro - 5 Elements Only :)

for long distance bikers its very useful to have gps support (sports-tracker with open street maps :))
or just to recharge gsm/mp3/gps

but need to charge mobile - my is nokia E72
this is excellent phone but after 6 hours on GPS the battery ends
one options is to go and charge on gas station/cofee
or to recharge it with portable device
I try one that use 1 AA battery, but it cannot even charge the phone - it works 20 min,
battery was hot and nothing. The other option was to use 6V accumulator with  one diode to get near 5 Volts
but it wrecks phone battery very fast.

so my Phone needs 5 volt from USB or charger
so i start searching how to charge it in other way
so - dynamo , but with 4 diode rectifier "gretz" and 7805 voltage regulator and i get - 3 V
i need 5, even with 40 km\h - 3,4 V

after checking internet its easy:
Nokia sale such equipment - 70 E
its too expensive
so decide to build myself
here i read about some equipment:
to build - 17 Euro
but after buy all elements, make custom plate for soldering
something goes wrong.
The scheme is hard to make - it uses MOSFET transistors, which are very weak - you can broke them with usual soldering equipment, and its hard to make backup scheme for long road.

"every one knows how to with a lot of money..."
but i found cheap way:

Step 1: Materials

I needed:

2 diodes
2 capacitors (16V 1000uF electrolite)
1 7805 - this is voltage regulator - if you have 7 - 40 V DC - you get 5 stable DC
cables and conectors

good practice is to have waterproof conectors, hot silicone gun
and to have backup circuit in emergency case

on first figure is Delon circuit
which is voltage doubler
so we get about 12 V DC with small current, not 0,5 A but small
on second figure is 7805 - positive voltage regulator
if we have DC min 7 and 40V max we can get stable 5 volt
its good practice to have good radiator for this element

Step 2: Making

its easy
dynamo give 6V 3W AC - it will be our sorce with 0,5 A current
we need 0,15 - 0,20 for charging our Nokia Device
some part of this is wastes since we doubled the voltage and current suffer

according to scheme
1. we connect 2 diodes and 2 capacitors (16V 100 uF electrolyte)
1.1 we check where if there is + and -
1.1.1 check voltage - around 12 - 14 V DC

2. after that we connect 7805
  1st pin - + 7 to 40V
  2nd  pin - minus in, minus out, ground
  3rd pin - stable 5V +
2.1 good practice is to use radiator to remove the heat from 7805, but in not necessary
2.2 check voltage - 5 volt stable not depending from speed of dynamo +- 0.1 Volt

3.connect all wires (from old charger we can use the cable and conector),
3.1 connect input with cable to dynamo - no polarity

4. Troubleshooting check voltage
4.1 on dynamo - 6 to 18 volts AC depending from speed
4.2 on nokia connector 5 volt DC stable
4.3 on scheme - check polarity of elements, reasembl soldering
4.4 post you situation on coments


electrolyte capacitors have polarity!
on them is grey strip with minus which must be connected to minus pole (see attached image)
diodes have polarity - white strip is cathode (see attached image)

scheme is tested and working

Step 3: Ready...

in working  mode it looks like this

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    10 years ago on Introduction

    Nice and simple design. But I have a question. Most Dynamos, and I imagine the Union one in your picture, output 6V. This is below the 7V min required by the 7805, or voltage will drop to below 5V. So what voltage do you get in practice, have you measured it? Could this be a problem with some phones?


    Reply 4 years ago

    sorry for loong delay

    voltage double scheme is doubling voltage - the scheme is with two capacitors.