Solar Powered Phone/Ipod Charger

Discussion in 'The Projects Forum' started by Zaper, Aug 25, 2010.

  1. Zaper

    Thread Starter Member

    Aug 17, 2010
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    I found a schematic online about how to make a solar Ipod charger which is attached below and I just had a few questions about it.

    First: would this be able to be used to charge a phone also?

    Second: will these parts work in this circuit?
    Solar Cell: http://www.mouser.com/ProductDetail/Parallax/750-00030/?qs=br5LzTWxXo6l6yR3XlCfKQ%3d%3d
    USB: http://www.mouser.com/ProductDetail/Harwin/M701-220442/?qs=x6EjVpvqMVNuYRinrmIdlg%3d%3d
    LM317T chip: http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/LM317T/?qs=sGAEpiMZZMtUqDgmOWBjgERttl15X3N66MYNkt0Ug6Q%3d

    Third: what should I use as a blocking diode?

    Fourth: would it be possible to put in an LED that would light up when it's done charging without a ton more stuff added?

    Thanks
     
    Last edited: Aug 25, 2010
  2. tom66

    Senior Member

    May 9, 2009
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    I don't see why there is a 'blocking diode'. You can omit it; the LM317T is protected from reverse voltages.

    There was something about charging iPhones and iPods from USB; there have to be some resistors on the data lines for the iPhone/iPod to charge. This was an attempt to stop non-Apple chargers from working. But you shouldn't have problems with a normal phone.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    I do recall reading about that. Apple chargers apparently have 5v on 2 pins.

    I would do some research into "charging ipod/iphones" to see what others have done.
     
  4. tom66

    Senior Member

    May 9, 2009
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  5. Zaper

    Thread Starter Member

    Aug 17, 2010
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    I looked at ways to wire it differently for the Ipod but didn't ind much. That's not really a big deal though. The person that created this originally used a 6v 250ma solar panel. The one I found to buy is 6v and 167ma. Will mine still work?
     
  6. tom66

    Senior Member

    May 9, 2009
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    Probably not. As that article appears to show, the iPod needs at least 250mA at the lowest charge rate.
     
  7. Zaper

    Thread Starter Member

    Aug 17, 2010
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    If not for the Ipod would it work for just a phone?

    And If not could I just buy like 3 92ma 2v cells and it would just "stack"? Sorry if that's a dumb question, I'm new to this stuff
     
    Last edited: Aug 25, 2010
  8. tom66

    Senior Member

    May 9, 2009
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    It could work for a phone, but without specifying your phone or the charger's ratings, I can only guess.

    Stacking three 2V 92mA cells would get you 6V at 92mA, not 6V at 276mA. Currents only add in parallel; if you had them in parallel, you could get 2V at 276mA. If you had nine cells in a 3x3 grid, you could get 6V at 276mA.
     
  9. Zaper

    Thread Starter Member

    Aug 17, 2010
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    ok well I think my phone's battery either puts out or takes in 950mA it says so that should be like a 3x5 with a 2v 200mA cell or thereabouts?

    Does 950 seem like a lot because if an ipod only needs 250 why would a phone need 4x more?
     
    Last edited: Aug 25, 2010
  10. tom66

    Senior Member

    May 9, 2009
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    950mA is quite a lot. What phone? Is it charging over USB? Most phones I've seen take a maximum of 500mA at 5V.

    Remember a LM317 requires 1.5V more input than output. So you might need 6.5V or 8V solar cell input.

    OR, another solution is to use a boost converter. If you can get hold of a 2V/3A solar cell (quite a lot, quite big), you can make a boost circuit to take 2V and output 5V. Less cells, but more work on getting the converter IC and soldering up a circuit. The great thing about this is that it will work even when there is less sunlight, as it boosts the voltage to meet 5V.
     
  11. Zaper

    Thread Starter Member

    Aug 17, 2010
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    well where I found the 950 is on the battery it says lithium-ion blah blah blah 3.7 v, 950mAh but i dont know if that's input or output

    also the phone is an enV touch
     
  12. tom66

    Senior Member

    May 9, 2009
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    Ah; that's the capacity of the battery, not the charge rate. 950mAh means it can provide 950mA for one hour or 95mA for ten hours or any combination you can think of. Look on the charger, the part which plugs into the socket. It should have a label on it.
     
  13. Zaper

    Thread Starter Member

    Aug 17, 2010
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    ok the charger says 100-240v - 50/60hz and .2A which i guess would be 200 mA
     
    Last edited: Aug 25, 2010
  14. tom66

    Senior Member

    May 9, 2009
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    Output voltage?

    200mA is easier to handle. You can use the boost circuit I described or the first circuit you posted; the boost one would be more efficient and charge faster under poorer conditions, but the first circuit would be much easier for a novice to construct.
     
  15. Zaper

    Thread Starter Member

    Aug 17, 2010
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    yeah this would be my second project with this sort of thing so I wouldn't want anything too crazy thrown at me. output is 5.1v and .7A
     
  16. marshallf3

    Well-Known Member

    Jul 26, 2010
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    It will take a lot of cells for any of the devices. They typically use LiION batteries, many of which almost inisist on a fairly high charging rate.

    The "Fuly charged" part of my phone is in the phone itself and probably operates off a signal that comes from the battery pack.

    Seems to me (aside from tricking the iPod) all you'd ever need is 5V at 1A. Harbor Freight may already make one of these, or Goldmine is a good source of slightly damaged but still 100% functional cells at good prices. I'd actually use something like a LM2575-5.0 IC in the circuit, it can compensate for varying cell outputs with very high efficiency.

    In effect you end up with a universal device that can be used on almost anything that charges or needs current from a USB port.
     
  17. tom66

    Senior Member

    May 9, 2009
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    Hey, wait, where did .7A come from? You said .2A(?)

    Make sure you're not reading the primary input current. Though, at 120VAC, 200mA is 24 watts, which is a lot of power, far too much for a phone...
     
  18. Zaper

    Thread Starter Member

    Aug 17, 2010
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    here's exactly what the charger says:

    INPUT
    100-240v - 50/60hz .2A
    OUTPUT
    5.1v then some lines and dashes and .7A
     
  19. tom66

    Senior Member

    May 9, 2009
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    Hmm well 700mA is difficult again. 5.1V output is unusual but it's probably the nominal output and ±5% allows for 4.84V to 5.35V. 200mA is the AC adapter input, that's probably waaaay over-rated because 24 watts isn't trivial to get rid of. You will need a lot of solar cells, or one large panel to get the required output.
     
  20. Zaper

    Thread Starter Member

    Aug 17, 2010
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    So is this not really feasible? I was thinking just something small. Hopefully not more than like a 6"x6" max
     
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