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When do you use a null node?

Discussion in '101 Display Basics' started by wanderanwills, Nov 18, 2017.

  1. wanderanwills

    wanderanwills New Elf

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    Hello,
    I have made up 3 star/spinner/flakes with 156 pixel nodes, 12volt, WS2811 chip. I run a Pixlite controller. 2 of the star/spinner/flakes run well but the other which is further away seems to get stuck on a certain pattern, I am assuming once the data gets complicated it is freezing on the one sequence. The cabling is about 13m long to the model. Is this where i need a null node to repeat the data signal??
    The other 2 star/spinner/flakes are 4m (cable length) and 9m, and they work fine.

    Regards
    Stephen
     
  2. ryanschristmaslights

    ryanschristmaslights Senior Elf Administrator Generous Elf

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    TL;DR It sounds like a null pixel would solve the 13m issue.

    Pixel data can only travel a certain distance before it deteriorates to the point of being corrupted. Null pixels are useful on long runs as they regenerate the signal (the same as a regular pixel would), and the data can go a little bit further before your first pixel (or another null pixel). The distance between your controller and first pixel typically can be longer than between different pixels. I like to think of null pixels like Chinese whispers where the null pixel has an ear piece to hear what the original word was at the other end of the long cable :D (the cheat! :eek:)

    With a PixLite 4, I could get some pixels working perfectly over a 12 metre run without a null pixel off one output, but with another output and identical pixels I needed a null pixel at the 9 metre point to make it the whole 12 metres (I was using Ray's 3-metre 13.5mm extension leads). If I put the null pixel at the 6 metre point, then I needed a second null pixel at 9 metres, too.

    One way around long pixel data run problems, particularly if you have a lot of them, is to use differential controllers (Falcon F16/F4 with differential expansion/receivers, or PixLite 16 Long Range + long range receiver).

    Of course, someone else may have a better explanation :)
     
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    wanderanwills

    wanderanwills New Elf

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    Hi Ryan,

    Thank you for your prompt reply and information.
    I have made up a null pixel that plugs inline and it is now working as it should be.
    Thank you gain.

    Regards
    Stephen
     
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    wanderanwills

    wanderanwills New Elf

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    Checking through lighting configurations, it has been noticed that adding the node has put the lighting order out on the star/spinner/flake by one node.
    When i added a null node on the pixlite 16 configuration software for the Star/spinner/flake 1(the once which has the long cable run and needed it) its nodes go out even further order and Star/Spinner/Flake 2 on the next port and universe is also now affected?? Star/Spinner/Flake 3 is not affected?
    Am i missing something?
    Regards
    Stephen
     

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