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Thread: Dodgy pixels in my setup, what has gone wrong??

  1. #1
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    Default Dodgy pixels in my setup, what has gone wrong??

    Hi,

    I'm starting to have problems with one of the universes on my christmas lighting install.

    I have a pixel star (60 pixels) connected to the controller, the data from the last LED on the star then passes through 4 x 27 pixel 'radial' sticks at ground level. Pixels are all 5V WS2811.
    I have plenty of 5V injection points in the whole system, it all used to work absolutely fine....

    Having gone away for a week and now come back to torrential rain I have a problem (I think) with the data line. The serial data from the star goes through about 4m to the first of the radials, each of which has 27 pixels. The data from each radial feeds into the next (length is about 2m in each case.)

    see this video for the installation, star is at top of megatree, the 'radials' radiate out from the bottom of the tree.

    In terms of the links and lengths overall the install looks something like this

    Controller universe --> 2.5m --> 60px star --> 4m --> 27 px radial#1--> 2m --> 27 px radial#2 --> 2m --> --> 27 px radial#3 --> 2m --> 27 px radial#4

    Now the star is 100 % fine and behaving as it used to, radial 1 is a little 'flickery' i.e. can see random colours sometimes at random brightnesses when 'on'. Radials 3-4 get progressively worse. Running pure white (in Vixen effect preview mode) all looks good, running a colour (say blue) is where things start to go wayward.

    I am thinking the problem is possibly with the final LED on the 'star' since I'm conscious that each LED passes data to the next. Maybe something has got wet at some point and the data out from this LED shorted to ground? I have used waterproof connectors throughout, but it has been crazy wet. They kind of follow what they should be doing, but not exactly. Certainly if there's no sequence playing they are 'off'.

    I also note that the controller has a series resistor on all the data lines, would it be wise to put a resistor between the lengths further down the chain too? What value?
    I'm conscious I might need to replace the last LED pixel on the star too....

    I don't follow why the issue gets progressively worse down the 'radials' however since they all have the same length of serial link between them, and they 'forward' the data between themselves.

    ***Further discovery***
    If I turn on about 30 or more pixels of the star (preceding pixels) full white, so about 50%, then the problem goes away.... Those 30 pixels can be any combination, they do not need to include the last pixel necessarily (pixel #60). Really confused now... ... It's not a PSU problem since the PSU is common to the whole display. Also if I temporarily shorten the lengths to/from the star to more like this, everything behaves too.
    Controller universe --> 0.5m --> 60px star --> 1.5m --> 27 px radial#1--> 2m --> 27 px radial#2 --> 2m --> --> 27 px radial#3 --> 2m --> 27 px radial#4


    Thanks
    Richard
    Last edited by RichieNorthcott; 12-21-2019 at 09:58 PM.

  2. #2
    Join Date
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    Default Re: Dodgy pixels in my setup, what has gone wrong??

    The problem is usually one of these:


    • The last pixel that works perfectly is sending crap to the rest.
    • The first pixel not working has developed a hearing problem.
    • The Data wire between them has gone bad.
    • The ground wire between them has gone bad.
    • A nearby injection point has gone bad and the voltage is fluctuating.


    Each has a different solution.

    As for the rest getting progressively worse, you are seeing a prime example of GIGO (Garbage in - garbage out). After the first non working pixel, nothing else matters.


    2020 Full sized show reworked for the new location. Only adding (famous last words) 13 RBLs that I finally got converted to using pixels
    2019 - Just moved into a new home (yet another change of plans). Will be dim but not dark. Too much to do at the new place to leave time for a show. Dim show (3000 pixels) had regular visits most nights.
    https://www.youtube.com/channel/UCyX...ttrsZNARkUce0Q

  3. #3
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    Default Re: Dodgy pixels in my setup, what has gone wrong??

    Thanks - I sorted it, I replaced the link and connectors between the star and the rest of the system. It's just a 2.5m cable with a couple of 4-way waterproof connectors

    Weird because the original cable tests fine with a meter. The new one has thicker wires, maybe that's helping...

  4. #4
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    Default Re: Dodgy pixels in my setup, what has gone wrong??

    I lied - it was kinda sorted but still had issues.

    The solution was to put a low value resistor in the data line at the 'out' of the star before the long run to the 4 'radials'. I also swapped out the final pixel in the star for a new unit in case it was faulty. I tried 2K which didn't work (I had some to hand!), 120 ohms did the trick however.

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