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Bicycle dynamo power center usb 5v charging 9v output

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piccas

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Hi all, this is my first post on what looks like a very interesting website. i have already read the other posts on this subject but haven't found what i am looking for.. so its time to start a thread.

what i am trying to build is is a complete system fitted in a plastic box where i can hook with a connector the cable coming from the dynamo, (the backlight takes its energy directly from the dynamo since it is already behind and has a circuit dedicated), has a usb charger output for a phone, so at least 500mA are needed, and when not charging any usb device (activated by switch) it should store the energy in a battery, from which i could later power a 9v radio which uses maximum 150mA.

i have tested my dynamo with just the voltmeter connected and the bike upsidedown and the max i reached was 27V. pedaling with the backlight on i got more or less 10V.
but i have read aound something regarding the dynamo being unloaded and how it affects its voltage.

i have already made a scheme from what i have learnt from other sites but i am sure there are a lot of mistakes.
View attachment 65010

for c1 i was thinking of using a few 470μF/35V hooked up in parallel (i got 4 from an old screen with all other caps, and if possible i would like to use as much of these as i can)
as for c2 it would be 0.1μF but i have seen it placed in parallel with c1 and with a value of 0.47μF, and other times in parallel with c3 as i have drawn, i must admit i dont fully understand the purpouse of this component. it is for stabilizing the current but why 2?
c3 instead i tought 22μF / 25V would be ok, a bit different from the original in the other circuit (22μF /16V) but at 16V i only have 100μF and 1500μF.

i still have serious doubts about the 9V part, and what type of battery to be used. ideally for size and weight a Li-ion battery would be perfect, but i have read that they will get damaged easily, and since they are so expensive it dosen't look like the solution.
the radio also works on lower voltagesalso 7.5V is great and that is the voltage the batteries
i found (no Li-ion at 9V) on farnell.com.

for the 5v voltage regulator i found this LM2940CT LDO
you can see it here
https://uk.farnell.com/national-semiconductor/lm2940ct-5-0/v-reg-ldo-5-0v-2940-to-220-3/dp/9490191
and the 9 volt
https://uk.farnell.com/national-semiconductor/lm2940t-9-0/ic-v-reg-ldo-9-0v-2940-to-220-3/dp/9493514

another important part is a led to indicate when the battery is fully charged but although really basic i woldn't know how to do it.

all corrections will be much appreciated, since like that i can understand better how this works! ;)

actually thinking this straight , it will never be able to charge a 9v battery. what if i would get it to charge 3 AA batteries? the radio needs 6 of them so mabie charging 3 one day, 3 another, it could be possible to keep it running for long.. tell me what you think
 
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Your link to the attachment doesn't work :(
 
That's better :). Before building the circuit you need to do some more testing of your dynamo output under different loads. If the back light (what current does it draw?) pulls the voltage down from 27 to 10 then you may have problems getting much current at anything over, say, 6V.
 
i will do further testing but my belief is that when i tested the dynamo unloaded, the bike was upsidedown and the wheel was turning much faster than when i was riding in the street dodging cars and eventually looking at the voltmeter in the back. the backlight is just a few leds with a printed circuit so i doubt much draw at all.
how can i know how much current is drawn? the dynamo (if so it can be called) is in AC but my multi pourpose voltmeter only measures DC.. am i missing something important here?
 
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ok so i tried measuring the current with a resistor, but i think there is a problem. i only managed to get 1mA with a 18K resistor, and the light was very dim. so i took out the resistor and the light was still very dim.. whatever speed i spun the wheel. actually at lower speed it performed better. i think it's the "hot spot" shown here http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm
i opened the led case and it seemed to me that i could smell the typical odor of gone components, but i dont know, since it still turns on..

anyway the 9V battery is just too much, but since i'm camping a detachable torch with a good batterylife would be good.
any ideas??
 
I did a quick look around online and most bicycle dynamos are rated at 3 watts at 6 volts (500 ma) and the higher powered ones are 6 watts at 12 volts.

Thats not much to work with considering that to charge most cell phones off a 3 watt 5 volt USB type power source it takes around 2 hours or more.

Or you could just buy a factory made USB port based system for around $32 plus you even get the mounting brackets plus phone and accessory holders with it!
**broken link removed**)

Either way I don't know about you but I have a hard enough time motivating myself just to answer my phone so cycling vigorously for two plus hours to charge it first is definitely out of the question! :eek:
 
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well it's not so much for phoning but for the gps. i am going for a bike trip and i thought it would be useful to have maps and to record the trip, so i would have the phone charging while using the gps, i would probably leave the sim card at home :)

buying one is certanly not an option, i am against all of this gadget comsumptio, and i am sure they will brake in no time, if i build it i cann also repair it easily.

i have rethought the project over, and i'll leave out the 9V part. but as i said i will try to make a torch out of it, so that it will serve in the evening while camping. would it be possible to store enuogh power in C1 if i made it of capacitors connected in parallel, lets say, 7 X 16V/1500μF to power the led/s afterwards?
 
7 of those capacitors is only ~10mF total.....nowhere near enough to power a bunch of LEDs for very long :( IMO you'd be better off charging a battery (3 or 4 NiMH cells, depending how fast you ride :)) fully at home and using the dynamo to top-up any charge used by whatever you power with the battery. Try Googling for 'constant current charging circuits'.
 
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