LM7805 Making Cellphone shut down

Discussion in 'General Electronics Chat' started by imzack, Apr 18, 2012.

  1. imzack

    Thread Starter Active Member

    Nov 3, 2010
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    Ok, im trying to make a cellphone charger from a batterypack, i have 7.2 volts going into my lm7805, I wired it up correclty i believe. I think attach the Vout and the ground to my cellphone wires, i hook the cellphone cable to my phone.

    Once i do this, the cellphone turns off and the LM7805 got SUPER hot, i unplugged it, assuming its getting too much current for some reason.

    Does anyone have any idea why this is happening?


    Any suggestions?


    Thanks


    Zack
     
  2. nerdegutta

    Moderator

    Dec 15, 2009
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    Would be nice with a schematic. Are you using a car charger?
     
  3. imzack

    Thread Starter Active Member

    Nov 3, 2010
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    no, I have 18, 1.5 volt cells. 3 strands of 6. so 6 batteries in series giving me 7.2 volts and three of these in parallel.

    ill see about a schimatic
     
  4. imzack

    Thread Starter Active Member

    Nov 3, 2010
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  5. nerdegutta

    Moderator

    Dec 15, 2009
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    Do you have the heat sink?

    What are the values on the caps?

    You sure you haven't turned the IC the wrong way?
     
  6. imzack

    Thread Starter Active Member

    Nov 3, 2010
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    .33 micro farads electrolitic cap, and a .1 micro ceramic(on the out end)
    um no heat sink, it turn the phone off immediatly though

    and the ic ive double checked.... looks good to me...
     
  7. nerdegutta

    Moderator

    Dec 15, 2009
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    Have to ask, but have you checked for shorts, solderblobs and stuff like that. I suspect there is a short somewhere. How's the cable you connect to the phone?
     
  8. imzack

    Thread Starter Active Member

    Nov 3, 2010
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    solderblobs?> what is this and how does it affect the circuit?
     
  9. nerdegutta

    Moderator

    Dec 15, 2009
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  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    1,393
    Here's a quote from the description of the circuit in your link. "This resistor does a very important function of current limiting and restricts the flow of excess current into the phone."
     
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