USB Car Charger

Discussion in 'General Electronics Chat' started by rjojjr91, Mar 24, 2013.

  1. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    I have put to gether a phone charger for my car, with a few resistors(to spread the heat) and a 5 volt voltage regulator. This temporary until my switching regulator arrives.

    The problem is, my phone says it is charging, but the batter is actually discharging. Can anybody help.

    I have used the same setup before with 8 AA batteries to charge an ipod, and that worked. I just don't get why this wont charge my android
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.

    There is a chance this is a restricted topic, automotive electrical are not allowed here, but it sounds like you are wanting a simple phone charger that goes into a cigarette lighter. This is allowed.

    Without schematics I won't even try to guess what you are asking. Schematics are the true language of electronics.
     
  3. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    Here is a schematic, it always worked with my iphone when I had one. With my android, it say's it is charging, but discharges quick.

    [​IMG]
     
  4. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    How do I upload a picture?
     
  5. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    [​IMG]
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    @rjojjr91 Are you sure you posted the right schematic? A 7905 is a NEGATIVE regulator. The zener is being used a s a pass diode rather than in zener mode. Or else the polarity of the source is backwards. At any rate, I don't think the circuit would work as drawn.
     
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Not to mention a linear regulator. At 12v volts regulated down to 5V you are going to have an enormous heat loss. You have a chance of starting a fire in our car and certainly drain the battery down to nothing.

    Just go buy a charger at the discount store. They are $5 US. Not worth building.

    If you insist on building your own then use a switching regulator. Those cheap charger use the 34068.

    A better but still easy to use switching regulator would be the LM2675 from TI.
     
  8. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    I am working on building one with a LM2675 when it comes, but I put the resistors in to help dissipate the heat. And that is supposed to be a positive linear regulator, and I forgot that I have a switch. Does anybody know though, why it is discharging my battery?
     
  9. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Why are you wasting your time with the linear regulator then? If you forget to unplug the charger, you could come back to a dead battery.
    You are probably more money to build one than buy one.


    The 7905 is a negative regulator. Read the datasheet.


    What do you think is causing all of that heat?
     
  10. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    I am not an idiot, the regulator is different than the one on the datasheet, that is why I put the caption, and it is not draining my car battery, it has an on off switch. It is draining my phone. I had the same setup a year ago with 8AA batteries, and an iPhone, and it worked just fine. I just don't get why it does not work now on my android.
     
  11. rjojjr91

    Thread Starter New Member

    Mar 24, 2013
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    And the AA version did not have the resistors.
     
  12. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    You are going to go far here with an attitude like that. I am sorry I tried to help now.

    You asked why was your battery being discharged you never mentioned which battery.
     
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