Help with 14.4V to 12V resistor

Discussion in 'General Electronics Chat' started by twizted91gt, Jul 24, 2012.

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  1. twizted91gt

    Thread Starter New Member

    Jul 24, 2012
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    OK i installed a 12V backup camera in our VW and am having a problem. Im just shy of clueless when it comes to electrical issues so cut me alittle slack.
    Camera is grounded properly and tapped into the reverse lights for power to turn on. When the car is OFF with key turned and put into reverese camera works perfectly. Comes right on clear as day.
    When Car is ON and running the camera doesnt work or comes on with a squiggle of lines.
    The only thing that i can think of is that the camera is rated for 12v operation and when the car is running its putting out 14.4 or so.

    SOOOOOO i had a friend use a mulitmeter to load down the power into the camera to a steady 12v and DING it came right on.
    Can anyone recommend some sort of resistor or regulator that can be wired in-line to keep the camera seeing only 12v? I asked a radioshack guy to help and he was clueless.
    Thanks guys for any help with this.....
     
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  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Return the POS camera. Its a pile of junk if it can't stand typical automotive voltages. 13.8-14.4V during charging is NORMAL. Or something is wired wrong.

    I'd love to know how you "used a multimeter to load down the power into the camera to a steady 12V" too..

    Oh and automotive topics are not allowed on this forum due to safety concerns.
     
  3. twizted91gt

    Thread Starter New Member

    Jul 24, 2012
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    OK easy there guy,,,,no need to get all angry. First off its a Clarion camera that came with our Clarion Navi unit. So its NOT a piece of junk. Second off i said i wasnt too electronics saavy so maybe it WASNT a multimeter but it was some fancy electrical tool he used to load the voltage down to 12v.
    Camera has a simple ground and power so its not wired wrong.
    "safety concerns"? what does that mean? Someone can get hurt asking an automotive related question?
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    YES. The owners of this forum have forbidden discussions of automotive topics due to safety concerns (messing with wiring causing a crash,etc..).. I think its silly in some situations too but its not my forum.
     
  5. K7GUH

    Member

    Jan 28, 2011
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    You have tapped into the backup light circuit somewhere after the switch which turns the backup light on. Anything you do to your car's wiring is a potential risk, especially if, as you say, you are confused by electrons whether at rest or in motion. Hence the prohibition on automotive topics.
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Back in the auto stereo market, Clarion was not known for high quality. I agree a 12V camera that cuts out at 14V is pretty worthless but if you want to "fix" this just use an LM2940 or LM2941 LDO voltage regulator to lock the camera power voltage at 12V while it's at 14V system voltage. As long as the camera draws under 1A, no worries.
     
    Last edited: Jul 24, 2012
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    In this case there is a (remote) chance you might blow a fuse and take something out when you "piggy back" some electronic device onto a line in a car. In theory, the line is fused to run whatever it's designed for and not other appliances so it might pop a fuse. In general, it's better to run added electronics off an "auxiliary" output line which is intended to run external stuff like a laptop.
     
  8. twizted91gt

    Thread Starter New Member

    Jul 24, 2012
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    Yes the camera power wire is tapped into the reverse light wiring but everything is done very neat and soldered/heat shrinked cleanly. I may not know what im doing but i do the things i know neat and correct.

    bountyhunter---- Is this 2940/2941 your standard regulator from radioshack? Just a small 3 pronged unit? Im assuming its going to be a In/Out/Ground setup?
    Thanks for the help everyone.
     
  9. absf

    Senior Member

    Dec 29, 2010
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    May be the datasheet of LM2940 would help a bit. You'll need the schematics on P1 and pin assignments on P12.

    Allen
     
  10. #12

    Expert

    Nov 30, 2010
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    I did one of these this morning using:
     
  11. twizted91gt

    Thread Starter New Member

    Jul 24, 2012
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    Yea guys I have no idea what all that means. Im looking for something in laymans terms.
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    But you don't know basic electronics or you would have understand what I said about possibly overdrawing that line and blowing a fuse.

    Do you even have any idea what current load the camera draws?
     
  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Camera = garbage :p
    You = Out of Luck :D
    Have receipt = Return Ok

    Just extend the wires by about 100ft.. that should take care of it..really it will
     
  14. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Get a LDO 12V regulator. Put some ignition filtering caps and u are all good.

    Simple as making pie. Even though I never made pie.
    But I doubt u had either.

    So in dummy terms.

    LDO is a low drop out regulator. Oh wait there is a simple way.

    Find a diode 1N4001. Put this in series with positive wire. Cathode goes to camera. Anode goes to supply. Put a 100n ceramic cap from diode cathode to ground and a 10uf 50V in parallel with the ceramic cap ..test it And post back
     
  15. Wendy

    Moderator

    Mar 24, 2008
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    As has been mentioned, the owners of All About Circuits has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

    This thread is against the AAC forum rules, Chapter 6, as seen here:

    This can be found in our Terms of Service (ToS)

    Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

    Please try to understand the reasons behind this action, and feel free to browse and use the forums.

    You might find answers to your questions in one of these forums:

    http://forum.allaboutcircuits.com/showthread.php?t=54400

    Another good forum that shares many of the same membership is http://www.electro-tech-online.com/ . Good luck.
     
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