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aarond76's avatar
aarond76
Explorer
May 23, 2013

12 V plug question

I installed an LED TV last night i the camper. It has a transformer that plugs into a regular 120V outlet and feeds the TV 12V DC. The plug going into the RV is a round barrel plug that is hollow in the center. I bought one of these plugs last night so I can wire the TV straight to 12V power and use the TV when camping without hook-ups. My question is how are these plugs wired are for a positive / negative. Does the posistive where attach to the outside conductor of the barrel plug or the inner portion?
  • homedad's avatar
    homedad
    Explorer
    May 23, 2013
    It should state the voltage output and polarity on the transformer. I bought a universal transformer with adjustable voltage and interchangeable plug sizes and polarities at Radioshack. Probably wouldn't handle a TV, but would operate radios, fans etc.
  • boogie_4wheel's avatar
    boogie_4wheel
    Explorer
    May 23, 2013
    On the back of the television there will be a diagram next to where you plug in the power supply. It will show a '+' or '-' sign with a line indicating that the + or - is the center and that the other is the outside.



    You could also use a volt meter to indicate polarity as TT_Tim has attached the diagram. Place the red (positive) lead on the center, and the black on the outer. If you get 12V, then the center is the positive. If you get -12V (notice the minus sign), then the outer is the positive.
  • Weasel1USA's avatar
    Weasel1USA
    Explorer
    May 23, 2013
    What aarond76 said is the best advise and a very nice graphic of how to do it, unless you're using a analog volt meter, in which case the needle tries to go backward. In that case the center is the negative terminal.
  • TT_Tim's avatar
    TT_Tim
    Explorer
    May 23, 2013
    aarond76 wrote:
    So educate me. How do I check with a volt meter?




    If the digital readout is as shows (12.7) the center is wired to positive.
    If the readout is -12.7 the center is wired to Negative.
  • skipnchar's avatar
    skipnchar
    Explorer
    May 23, 2013
    Many of these type of plugs are designed for use with cigarette lighters (which don't CARE which way they're wired). Your TV probably does care so DO check it carefully.
  • ScottG's avatar
    ScottG
    Nomad
    May 23, 2013
    mbopp wrote:
    Positive should be on the center pin. I'd verify it with a voltmeter first.


    X2, verify - I've seen them reversed.
  • mbopp's avatar
    mbopp
    Explorer
    May 23, 2013
    Positive should be on the center pin. I'd verify it with a voltmeter first.

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