DC Power Jack Wiring

Discussion in 'General Electronics Chat' started by need_elechelp, Apr 9, 2010.

  1. need_elechelp

    need_elechelp Thread Starter New Member

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    Hi all,
    Looking for some quick assistance (easy one) on how to properly wire a 3-pin DC power jack. I don't need/want the switching pin. The positive pin I am assuming is the center. The switching pin I am assuming is the pin that does not have continuity when I test between it and the jack when inserted?

    Assuming that, gnd goes to the non-switching pin?

    Should I just leave the switching pin open? Ground it?

    I bought this one: http://www.radioshack.com/product/index.jsp?productId=2103611

    Thanks,
    b
  2. Bychon

    Bychon Member

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    The center pin goes to the sideways connector. The shell goes to the connector farthest away from the sideways connector. Do not connect the pin you aren't using.
  3. eblc1388

    eblc1388 Senior Member

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    I would test for the center pin and wire positive to it.

    Then I would solder negative to the remaining pins.
  4. alim

    alim Senior Member

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    I take it you have a power supply and an appropiate socket(jack), plug the power supply into the jack , check the pins where the voltage comes out , note the polarity, and wire accordingly.
  5. need_elechelp

    need_elechelp Thread Starter New Member

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    I don't have the power supply connected yet, I wanted to figure it out prior so that I can place the proper lines on my protoboard.

    I see two conflicting replies for the two similar pins that are non-positive. One states both remaining to GND, one states the furthest away should go GND.

    So, here is the schematic for the jack. The extrusion I am assuming is the center pin. The other two are the pins in question. Can someone explain this rudimentary schematic to me?

    [​IMG]

    Thank you,
    b
  6. Markd77

    Markd77 Senior Member

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    1 is centre pin. 2 is outside. 3 is connected to 2 unless the plug is in the socket.
    There is no guarantee which will be positive, not knowing your power supply. There is no solid convention. Some supplies that use this kind of plug could be AC.
  7. euncircuit

    euncircuit New Member

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    So from what I gather, you would connect power to pin 1 and ground to pin 3? And leave pin 2 unconnected? This makes sense to me, but maybe I'm missing something?
  8. creakndale

    creakndale Active Member

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    1) If your wall wart adapter outputs "+" in the center of it's plug with "common" (Gnd) on the outside of the plug, then on the Radio Shack DC power jack connect "+" to Pin 1 and "common" (Gnd) to Pin 2. Leave Pin 3 open as it serves no purpose for your situation.

    or...

    2) If your wall wart adapter outputs "common" (Gnd) in the center of it's plug with "+" on the outside of the plug, then on the Radio Shack DC power jack connect "common" (Gnd) to Pin 1 and "+" to Pin 2. Leave Pin 3 open as it serves no purpose for your situation.

    creakndale
  9. rjenkins

    rjenkins AAC Fanatic!

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    The center pin is positive.

    One of the other pins is negative, the third pin is switched to negative.

    Connect them both to circuit negative/ground. It does not matter which is which is which and for any connector the physical attachment to the board is important. That extra pin being soldered gives higher strength.
  10. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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    Pin 3 is in case you have an internal power supply (like batteries). They get switched out of circuit when you connect the external power supply. If the circuit has a decent capacitor the transition is seamless, and you don't use your batteries up (or blow them up overcharging them).

    I've seen plus and minus power supplies with that scheme. Look close at your use. A lot of Radio Shack adapters can go either way too.
  11. bertus

    bertus Administrator Staff Member

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    Hello,

    Beware, the middle pin MAY be positive, but CAN also be negative.
    Please check WHERE the positive and negative reside.
    A wrong way connection may destroy the connected appliance.

    Bertus
  12. rjenkins

    rjenkins AAC Fanatic!

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    Yes, sorry - I should have started with:

    Assuming you are using the commoner center positive DC adapter
    ...
  13. vick5821

    vick5821 Member

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    How do I know the center of the plug of adapter is positive/negative ?
  14. n1ist

    n1ist Active Member

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    Some wall warts have a sticker on them that shows the output polarity. Otherwise, use a multimeter.
    /mike
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