Discussion in 'General Electronics Discussion' started by JonRob1, Apr 7, 2015.

1. ### JonRob1

7
0
Apr 3, 2015
Hi, im attempting to create a device that charges a mobile phone through wind whilst attached to a bicycle.

I have quite a basic understanding
on electronics which is why i need help so here goes...

I have 4 motors/generators that can produce 0-12v each but on average whilst tested produce approximatly 2v each whilst cycling at normal speed.

I have managed to power any 5v phone with 4 aa rechargable batteries hooked up to an x in car usb phone charger that i have taken apart, but i cant figure out how to charge the batteries from the potential 8v i can produce from the small motors/generators.

I cant seem to figure out how to get the combind voltage from 4 motors, does anyone have any ideas? What ive got so far is hooking them up in series with diodes so they dont power eachother but the two ive put together so far only produce the voltage from one which is about 2v. Basically, if i have a hairdryer blowing a small fan connected to a motor/generator and that generator is producing a steady 2v, i want to then have another generator hooked up to that if i twist it for example and it produces 1v, the overall reading will be 3v. If that makes sense?

Im very frustrated and stuck so if anyone has any help i would be extremely eternally gratful!

2. ### davennModerator

13,947
1,989
Sep 5, 2009
hi there
welcome

tell us more about these 4 motors/generators
photos, links to info on them etc

Dave

3. ### hevans1944Hop - AC8NS

4,647
2,169
Jun 21, 2012
If each motor/generator has two wires (positive and negative) you should be able to wire four of them in series for four times the output voltage of any single one. No diodes required. Pay attention to polarity so the voltages add, instead of bucking each other: positive on first motor to negative on second motor, positive on second motor to negative on third, positive on third motor to negative on fourth motor. Take output between positive on fourth motor and negative on first motor. Make sure all motors turn in the same direction in the wind.

4. ### JonRob1

7
0
Apr 3, 2015
Hi dave, thanks for the intrest, this is a link to a pretty much identical motor/generator: http://m.ebay.co.uk/itm/131351396056?nav=SEARCH

5. ### JonRob1

7
0
Apr 3, 2015
Thanks for the reply! i will try this as soon as i get home, i did not think of this and i hope it works! Thanks again for your expertise will let you know how it goes,
Jon.

6. ### Colin Mitchell

1,416
314
Aug 31, 2014
You need a 12v version of the 2v motor.

7. ### JonRob1

7
0
Apr 3, 2015
It works well! Thanks a lot. With the battery charging, am i right in thinking its safe to wire the motors directly to the rechargable batteries with a diode?

111
43
Oct 14, 2014
No. You will want a circuit specifically designed to charge the specific chemistry of battery you're looking to charge. In other words, you'll want your wind generators to power the charger for those batteries. You'll want to make sure the charger can accept any potential voltage you could produce with the wind turbines without being damaged. Otherwise you'll just be putting some random voltage from 0 to ~10V on them at any given time. You also won't want to try to charge the batteries when they're full or overheating or in some other state where you don't want them to be exposed to an external power source.

Chargers that are designed to be powered by the cigarette lighter in a car are generally very robust in this sense (i.e. you won't have to do much to make it safe for your charger), but 8V is on the low side of what they might accept.

Also, those motors you linked to have a very low power output. A "slow" charging USB port will output 2.5W and each of those motors will only output. 0.05W. You'd need 50 of them (ignoring losses from efficiency) to charge as fast as a USB port on a PC. So I doubt you'll get much, if any, of a charge into them from 4 of those motors. You may not even be able to power up the charger.

davenn likes this.
9. ### JonRob1

7
0
Apr 3, 2015
If i used a buck converter such as this one http://www.ebay.co.uk/itm/LM2596-DC...700?pt=LH_DefaultDomain_3&hash=item3f3e928664 between the generators and batteries would this work to carry enough charge to the batteries?

10. ### davennModerator

13,947
1,989
Sep 5, 2009

no .... you obviously didn't read the first paragraph of garublador's last post ....
in particular the section I bolded ......

Dave

11. ### JonRob1

7
0
Apr 3, 2015
Thanks Dave, would i wire this myself, or would i have to buy a battery charger? im a complete newbie!

12. ### Gryd3

4,098
875
Jun 25, 2014
Personal Preference.
First, pick a battery type, then you can go from there.
Lithium is light and has a higher capacity than Lead-Acid, but is more susceptible to under/over charging.
Lead-acid is pretty simply to charge..but is heavy and large.

Of course, there is NiMh and NiCd as well that many RC cars and cordless phones use.

Once you pick a battery chemistry and a pack size, you can look into building a circuit to charge, or buying a circuit to charge. (If you go lithium, buy a charger... don't try to build this one yourself.)
NiCd and NiMh can be charged with pretty basic circuits and are also found in those solar power lawn/garden lights.

13. ### JonRob1

7
0
Apr 3, 2015
Thanks for the further comments and help, ive done some more digging and research and found hopefully some possible solutions (very hopeful).

As size is a big contributing factor i looked at the rc batteries and chargers that could possible work and were small in size. I found this one: http://www.modelsport.co.uk/etronix-micro-1s-dual-charger-500ma-x-2/rc-car-products/379043
Which i think will charge a 5v battery from a usb port of a computer so if i could replicate that it could possibly work, but as mentioned previously the power to charge could be a problem?

I then came across this:
http://www.fc-moto.de/epages/fcm.mo...l59_x9tjVKtuUCzI5Dxks-Q74SBCY3u27whoCBcnw_wcB

Which charges a phone from usb connection, again same problem possibly.

Lastly, i found this looking at the solar light chargers that were mentioned which i think looks the most promising:
http://www.amazon.co.uk/Instapark-INDC2405-Regulated-Converter-Transformer/dp/B00NEUDEFG

It needs 10v at least which then regulates to 5v but it says 3A which is more than enough to charge right? So im hoping that this would do the job if i connected all my wind generators to that maybe adding an extra one to get the desired 10v (needs testing)

Im sorry if ive missed anything obvious, as i said im a complete newbie at this, hope this helps and thanks in advance!

111
43
Oct 14, 2014
It can supply a maximum of 3A, but it won't be able to supply more power than it's provided. With 5 of those generators you're only at 0.25W, which at 5V is only 0.05A (minus losses from efficiency, so more like 0.04A). If this is an academic exercise to see if you can get it to work then that might be OK, but I really doubt you'll see any appreciable charge added to your battery with this method. If your phone is on it will probably just make it drain the battery slightly slower.

Besides that, it looks like you're on the right track.

15. ### Gryd3

4,098
875
Jun 25, 2014
Agreed.

I should clarify this. So far you have been looking at pre-made chargers. The only problem you will have with power, is not having enough. These chargers are built for, and meant for taking an input, and regulating the output properly for the battery it's meant for.
One of two things will happen, if you cant put out 'enough' power to one of these chargers.
A) The battery will not charge at all.
B) The battery will merely charge slower.

Now, if you are directly charging a phone, you don't really need to worry about battery chemistry so long as you can put out 5V and at least 500mA. (Should have mentioned earlier )

So far, good job. I think it's time to start experimenting. And as far as joining the generators together is concerned. I would personally put a rectifier on each one and connect the outputs of the rectifiers in parallel. This will create a lower voltage, but a higher current of pulsed DC (Which can be smoothed out with a capacitor)
I am unsure what kind of voltage you get though from one generator though.. so you may have to play with the layout. (Series = higher voltage less current... but because a generator does not produce DC, the AC may be out of phase or at a different frequency which is why I suggest using a rectifier on each generator)