Looking to make a solar powered iPhone charger

Discussion in 'The Projects Forum' started by njr53, Dec 16, 2012.

  1. njr53

    Thread Starter New Member

    Dec 16, 2012
    2
    0
    My parents live in Connecticut, where power goes out at least once a year. This year they went without power for almost a week (due to Sandy). I think it would be a great Christmas present to make them a solar powered cellphone charger. I could just buy one, but that's boring and not nearly as personal as building them one.

    I want to build two chargers. Each parent uses iPhones, and my dad has a work blackberry. I've looked at a couple tutorials (example), and get the gist of it, but have some questions. I plan on using these elements (ignore the multimeter, I don't have one at home) for my circuit. I plan on ordering one extra of each (except solar cells), in case I fry something.

    iPhone wall chargers have 5V, 1A output. Blackberry wall chargers have 5V, 0.75A output. Typical computer USB ports have 5V, 0.5A output.

    * Here is the solar panel I plan to use. I want to hook up six in parallel to theoretically output 540mA at 4.5V. Will this work on both phones? I am fine with slower charging. I don't know if the slightly lower voltage will work with the phone. There are other solar panels. As long as the panel output is within a certain range, I guess it comes down to which website is reliable, but what would the range be?

    * I don't fully understand how to hook up the diode. Will this circuit protect the solar cells? I read you need to do this in a tutorial. Why would the smartphone create a reverse current?

    * I want the red LED for kicks, how much will it harm performance and how can I minimize this? Hook it up in parallel with the other diode, or just lose the LED?

    * In steady sunlight, do solar cells' output fluctuate much and could this harm a phone?

    * Apple is kinda pesky in their charging system, and require 2V on the data ports of the USB for the iPhone to let in electrons. I would then need to add this to the circuit. Would this mod make the charger not work with a non-iPhone?
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    990
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,648
    632
  4. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    990

    And You will be spending a good chunk of the solar panel power just to run the regulator. What is needed is a buck step down convertor not a linear regulator.

    Linear regulators are simple but not very practical when it comes to solar panel charging.
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You should not buy a no-name-brand solar panel that has no datasheet. Instead buy a name-brand solar panel that has a detailed datasheet.
    Will it work on a cloudy day? Barely.

    Your circuit with a "4.5V" solar panel with a diode and a 2V red LED in series has an output of only 1.8V. You need 5V.
     
  6. njr53

    Thread Starter New Member

    Dec 16, 2012
    2
    0
    I don't want to buy one.

    Its a schottky diode, which has lower voltage drop than that. Also, I thought LEDs had much smaller voltage drops than 2V. I'll try to find one with a datasheet.
    What are name brand solar panels?

    Are the capacitors acting as a low pass filter? Is that what they are for? Where can I find a buck step down convertor or the necessary circuit diagram? Will it be so much loss that forsaking simplicity is worth it?
     
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    990
    Buck regulators aren't that much more complicated just a few more components. To keep it simple just buy one of those car usb chargers. Tear it apart and use the little board inside. The are usually based on the 34063. An older chip not the most efficient but there are tons of examples out there if you wanted to build your own.
     
  8. wayneh

    Expert

    Sep 9, 2010
    12,101
    3,033
    He needs a lot more boost than buck for the reasons AG stated. 4.5V just isn't going to do it without a boost.
     
  9. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    990

    Sorry missed the specs on the panel. Yeah sounds like a boost will be needed or better a bigger panel.
     
Loading...