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Power Injection Question

Discussion in 'Power Supplies' started by OzAz, Jun 11, 2017.

  1. OzAz

    OzAz Senior Elf Generous Elf

    Dec 29, 2015
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    in the picture is there a necessity to have the power feeding between the two strings of pixels?
    Assuming: controller output is 5VDC at 5A (25W) and each string of 50 pixels draws 15W; only two strings of 50 pixels.

    As per this wiring diagram?

    -V ---P---P--- V-
    D ---P---P
    +V ---P---P--- V+

    Or, does it have to have no power connection between the two strings, as per this diagram?

    -V ---P P--- V-
    D ---P---P
    +V ---P P--- V+

    So which of the three options is correct/better? Would it work with either of the two options above?
  2. foodi

    foodi New Elf

    Aug 31, 2014
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    maryborough victoria
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    i power mine from both ends if that makes sence using 2 diffrent power suplies onsay 300 nodes
  3. Kitman

    Kitman Full Time Elf

    Oct 25, 2014
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    Munno Para
    If you were to inject like that and have positive coming from the controller on a 5A fuse you will be looking at 30w being drawn which may end up feeding back through the fuse and blowing the fuse. However I am not 100% sure on how the load will be spread across the circuit so I will wait for someone else to advise on that.

    Most people will run the positive to the light separate from the controller and not draw positive and negative from the controller.
  4. Roosta

    Roosta Full Time Elf

    Dec 8, 2015
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    My 2 cents, every situation is different.

    Assuming your diagram and calculations, then first wiring description would be better.. Or as mentioned by Kitman, bypass the power to the controller and just have it feed the start of the string.

    Also worth testing is number of pixels before voltage drop becomes an issue..
    With my pixels this was roughly 80, which meant power injecting every 100-120 worked a treat..

    Also, regards foodi's comment, its bad practice to have 2 power supplies feeding a string of pixels unless done correctly, by isolating the 2 positive voltage feeds, but maintaining the negatives and the data.. you may also need additional power injection, ie if you had 2 strings of 100 pixels, running from 2 power supplies then you would need 4 power feeds, 2 from each supply to the ends of each of the strings, then tie the data and negatives together, or alternatively you could feed the power in at pixel 50 from one supply and pixel 150 from the other..

    Power injection is a funny beast and everyone has a different way of doing it, and some times practicality of the situation means not doing it the most efficient way..

    djgra79 likes this.
  5. scamper

    scamper Senior Elf

    Jan 5, 2014
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    With pixel controllers I make it a practice to use only the data lines if I am running more than 1 run of pixels.
    I am not saying it is right or wrong, but the way I see it is, I can live without a string of pixels if something goes wrong, I can't live without my controller, so I try and isolate it as much as possible.
    As far as running power to them, then I would run it at the start and the end in the above diagram assuming you are only running 2 strings.
    If you look at it like this, you have a mega tree with 50 pixels going up, then 50 coming back down. You can inject power along the bottom and not need to run power to the top of the tree to inject. Then you just join the data to come back down. Set it to zig zag in your controller and wholah!

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