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Some pixels acting odd

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by nato595, Apr 22, 2016.

  1. nato595

    nato595 Let's do this!

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    Hello!
    I'm having a super frustrating issue with my 12v square WS2811 pixel nodes, and I'm hopeful that someone can help.
    When running through an R-G-B-W-off sequence (or other sequences as well) when the command is OFF (after being on),*sometimes* *some* pixels stay on - usually Red. Usually one or two of the last 4 pixels on a 50 count.

    Details:
    I've tried 6 different strings, some in strings of 50, and others in strings of 100 with power injection at pixel 51. When a string of 50 usually 1 or 2 of the last 4 pixels. When a string of 100, usually 1 or 2 of pixels 46 - 50 and/or 96 - 100. Same pattern with a string of 150 as well.
    Using a 350 watt, 12V PS.
    J1Sys ECG-P2 controller powered from the same power supply as pixels.
    I've tried both universe outputs independently on the controller, both give same result.
    I've tried adjusting KBPS speeds in controller GUI, anywhere from 1500 to the default 3500.
    Test sequences performed from xLights and LOR Sequence Editor, both give same result.
    Multi-meter shows 12.6 VDC at beginning of string, 12.4 at end of string with no lights on, and 10.9 at end of string while all on White.
    I have less than 1' distance between the controller and pixel #1, so I'm positive it's not a lack-of-null-pixel issue.
    All lights respond 100% perfectly to ON color commands, just when off, some resort to red, *sometimes*.
    Which pixel stays on Red usually switches when continuously running the R-G-B-W-OFF routine as well; for example, all will go off, then next time #49 stays on Red, then next time #47 & #49 stay on red, then all off, then #48 on red, etc.

    The only thing I haven't tried is using a different controller... but this one has always served me well in the past. I can test a different controller in the future, but it will be a while until I'm able to easily do so, and was hoping to get a list of other troubleshooting ideas from you in the meantime.

    As always, thanks for your help!
     
  2. stanward

    stanward New Elf

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    Drop your power supply voltage to 11.9v or less and this problem will go away.


    Sent from my iPad using Tapatalk
     
  3. OP
    OP
    nato595

    nato595 Let's do this!

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    You were absolutely right! I've never heard of such a thing, but that was by far the easiest fix I could have made and no more issues. I'm at 11.85 now and all is well. Thanks so much!!
     
  4. BundyRoy

    BundyRoy Senior Elf

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    I'm trying to work out how this works. Can anyone explain it to me. Nato when you dropped the voltage and put the lights on full white do the last pixels look white or do they go a bit pinkish looking like you get when there is low voltage.
     
  5. i13

    i13 Senior Elf

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    They are 12V so the voltage drop is a smaller percentage of the correct voltage than with 5V. 10.9 volts at the far end would probably not have a noticeable effect on the colour.

    5V versus 12V is another topic worth fully understanding in the case of nodes and strips. They both have their advantages and disadvantages.
     
  6. OP
    OP
    nato595

    nato595 Let's do this!

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    No, not noticeably. Still looked as white to me as it did 10 minutes prior. Side by size 12.6v vs. 11.8v I'm not sure if a visible difference would be seen or not.
     
  7. BundyRoy

    BundyRoy Senior Elf

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    So can anybody explain to me why the problem goes away at a lower voltage. What causes the issue and why does it disappear when you lower the voltage. Is 12.6V too high and it somehow corrupts the data signal by the time it gets to the last pixel/s and hence they don't get the off signal. I've always set my power supplies at around 12.4V to help allow for voltage drop and I've never had an issue (yet). Am keen to get to the logic behind this fix if anybody can help. Thanks.
     
  8. i13

    i13 Senior Elf

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    Voltage drop depends on current draw. The amount of current drawn when the LEDs are on is significantly higher than when they are off. This means that pretty much the full 12.6V runs the entire length of the string of pixels when they're off so that is when problems occur.
     

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