Homemade USB-charger

Discussion in 'The Projects Forum' started by Alfanano, Feb 16, 2009.

  1. Alfanano

    Thread Starter New Member

    Feb 16, 2009
    2
    0
    Hi. I'm working on a little project that I decided to do after I bought 2 USB-chargers who got there power from AA/AAA batteries but I have ran into some problems and hoped that you could help me a bit.

    The components are:
    Battery pack for 4*R06 (generates 6 Volts)
    1 +5VDC regulator (LM2940T)
    1 100uF capacitor
    1 USB type A contact

    They are all connected like this:
    [​IMG]

    Checking with a voltmeter I get 4.95 V out but when I connect a USB product like cellphone or Ipod, it only reacts to that something is being connected but no charger icon comes up. So I guess that I have to do something with the to remain pins on the USB-port (D+ and D-). I read that using a 100k resistor and connecting it in a special way could trigger the units to charge but I have no idea of how
    So hopefully someone of you can help me what I should add to my circuit and how to make this work sucessfully.
     
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Don't quote me, but I think this might be the way to accomplish the task.
     
  3. Alfanano

    Thread Starter New Member

    Feb 16, 2009
    2
    0
    Thank you for your answer iONic. Took some time today and made a more professional wiring diagram then the last one. Put in the suggestion from iONic and the result became this:

    [​IMG]

    Do any of you think it will work or fry everything I connect?
     
  4. spectrum123

    New Member

    Nov 2, 2013
    1
    0
    I made a USB charger with a 9 Volt battery connector and a 5 volt regulator with a USB port. That charges everything I have.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    First a quibble - it's convention to put the higher voltage towards the top of the schematic.

    It won't fry if the polarity is right (I didn't check) but I don't think that will work. It puts full voltage on the data pins, albeit through the 10k. Most solutions I've seen require a voltage divider so that a specific voltage is applied to each pin. This fools the device into thinking it has been connected to a proper charger. The voltages required may (I'm not sure) vary amongst devices. So it may take some tinkering.

    Look up the Minty Boost project and I think you'll find all the info you need.
     
  6. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    Not even a LDO regulator will work with just one volt above the output, you need ATLEAST 8 volts for ANY 5V regulator to work.
     
    absf likes this.
  7. Oldi

    New Member

    Nov 1, 2013
    9
    0
    These is not true. LM 2940 Typically Dropout Voltage at 1A is 0.5V. http://www.ti.com/lit/ds/snvs769i/snvs769i.pdf
    For charging USB device it's better to have higher voltage, let say 5,3V - because of voltage drop on USB cable.
     
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