Problem with polarity on LED Strip

Discussion in 'General Electronics Chat' started by decept, Mar 22, 2012.

  1. decept

    Thread Starter New Member

    Mar 22, 2012
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    Hi Guys

    I'm having some issues wiring up a LED Strip, and was hoping for some advice on how to solve my problem I have this strip right here http://i.imgur.com/BG2if.jpg but from what it seems, the +12v is actually a ground, I've plugged this into my LED strip controller, and it didn't work, but once I reverse the wires it did, i double checked it and hooked it directly to a power source, same thing... Is there any way to reverse the polarity on this thing so I can use it?

    Thanks!
     
  2. n1ist

    Active Member

    Mar 8, 2009
    171
    16
    Most of those strips have a common anode connection to +12 and three cathodes (R,G,B) that get grounded through FETs in the controller. The silkscreen in your picture seems to agree with it. The only odd thing is the use of a black wire for +12; they did that so they could use red wire for the red cathode connection
     
  3. #12

    Expert

    Nov 30, 2010
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    No, you can't reverse the polarity of the LED strip without taking it apart and reversing every LED. Very messy. What n1ist is saying is that the black wire goes to + and the other 3 go to "ground" or negative, and they only used black for positive because they "used up" red to indicate the color of the LEDs it goes to.
     
  4. decept

    Thread Starter New Member

    Mar 22, 2012
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    If the LED strip can not be reversed how about the controller itself?

    http://imgur.com/gnZol,s4CMq,mXfMg (made sure to click ond second and third image)

    This is what I've learned, there are 2 controller that are identical to one another, other than polarity. The one I have uses the black as a common ground while each color is 12v, I need this reversed (or vice versa, i kinda lost over sight now). Is this possible?
     
  5. #12

    Expert

    Nov 30, 2010
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    None of those boards had 4 wires. If there are 3 boards in a controller, that would be a lot less messy to reverse.
     
  6. decept

    Thread Starter New Member

    Mar 22, 2012
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    no, its 1 board, i just took a picture of the top side, bottom side, and the knob that was on it
     
  7. #12

    Expert

    Nov 30, 2010
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    How does one board with 2 wires control 3 different colors?

    Oh. They have plugs on them.

    Well, it's still less messy to re-route traces on those circuit boards than to remove every LED in the LED strip.
     
  8. decept

    Thread Starter New Member

    Mar 22, 2012
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    yes sorry, the green blocks on the end are connectors, breaking it down to R, G ,B, and Common.

    How would I go about re-routing the traces to reverse the current in this thing?
     
  9. #12

    Expert

    Nov 30, 2010
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    I don't see how that will work either.
    This isn't turning out the way I hoped.
    You have three chances. I'm having a senior moment, you reverse all the LEDs, or you buy the right controller.

    A little help here, guys?
    I think I've messed up.
     
  10. BSomer

    Member

    Dec 28, 2011
    433
    106
    Couple of questions for you.

    Are the pads on the pcb accessible with meter probes?
    Can you probe each pad and find out which wire it goes to?

    It looks as though the pads I am referring to are labeled "+12, G, R, B"

    Now are you saying that the controller is set up for a common cathode and the led strips are set up for common anode (which it appears they are)?

    I cannot clearly see what the input is on the controller but the output seems to be labeled "VCC, B, G, R" which makes me think that the controller is a common anode. So I guess I don't know what the problem really is.

    edit: Okay I saw the other pictures. So the board should work with the led strip as configured but you say it doesn't unless you change the polarity of the input power to the controller right?
     
    Last edited: Mar 22, 2012
  11. decept

    Thread Starter New Member

    Mar 22, 2012
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    correct. I called the manufactorers, and they confrimed to me that the controller I have is reversed, so its a common - and RGB are +, where as the strip I have is common + and RGB is -
     
  12. RemediosMorthland

    New Member

    Mar 30, 2012
    4
    0
    This is what I've learned, there are 2 controller that are identical to one another, other than polarity. The one I have uses the black as a common ground while each color is 12v, I need this reversed (or vice versa, i kinda lost over sight now). Is this possible?
     
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