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Thread: WS2811 flicker but only at low brightness - Help please?

  1. #11
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    you might want to goto facebook official xlights support group and search for flickering. My best guess is that you need to change the refresh rate at your controller. as has been implied by others the specifications of 2811 has changed. one man changed his refresh rate from 40fps to 20fps and solved his flicker issues. I run all 12v pixels so the issues i have is ground lift. I solve it by adding a additional wire to ground from my psu.

  2. #12
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Contact Ray and ask him about the capacitor and resisters per the data sheet you have. He should be able to answer your question and let you know what you have.

  3. #13
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Hello all,

    I contacted Ray Wu and got the following (exact and full quote) reply,
    "hi Steve,
    sorry for that, i just talked with the engineer, he said they use a new version of WS2811 IC chip which has built-in the capacitor
    so there is no capacitor on the PCB, the capacitor has been put inside the chip
    he suggest every 50 nodes need an extra power injection point, could you try it again?
    and this is a promotion pixels with a very low price, so the quality is as good as our standard products
    so the quality is not as good as our standard products"


    A further reply from Ray Wu (quoted in full and exactly):
    "the factory use a special version of WS2811 IC with built-in capacitor
    i talked with the world-semi company,they said they produced this version of the ws2811 ic for the pixel light factory"


    I can not find any info that suggest WordSemi have included the capacitor internally to the chip - all the data sheets I have seen show an external decoupling capacitor is still required.

    What do people think of Ray Wu's response?

    Kind regards,
    Steve
    Last edited by pixel-newbie; 06-15-2020 at 07:59 AM.

  4. #14
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Hi, I don’t know what to tell you. Looking at the World-Semi site they are still showing a resistor and capacitor on the WS2811 series IC’s, that said the WS2812B-V5 is listed with an internal capacitor.

    Lastest major upgrade WS2812 series.
    The key points of upgrading are as followings:
    1).IC Internal Integrated Filter Capacitor.
    2).Reverse-connection protection.
    3).VCC/DIN/DOUT PIN instantaneously suppresses DC12V.
    4).Ensure color consistency even under 3.5V working voltage.
    5).Greatly improved the LEDcolor's consistency and brightness.
    6).Signal recognition range reduced to less than 2.8V.
    7).Improved EMC/EMI performance.
    8).All upgraded LEDs' defective rate < 1‱.
    As there's no change for the following things:
    mechnical size, timing, electrical&LED characteristics,
    we do not enable a new part number,
    only add a suffix version number to distinguish.
    Current version LEDs will last for around ONE year. (From 8th,Dec,2018)
    More details,
    Please check attached file instructions for reference.
    Given that that appears to be dated December 2018 in the time that has passed they could well have incorporated one into the IC as well, it would make sense to use the same dies.

  5. #15
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Promotional Pixels says it all .

    In a word they = junk and should be listed as experimental .

    A fellow hobbyist here in Canada had nothing but grief with those promo jobs.
    I believe he lost all his hair this past holiday season in trying to solve them with injection and so forth.
    Maybe see if Ray will return them for some that are suitable to your needs and this hobby .
    Last edited by angus40; 06-15-2020 at 05:41 PM.

  6. #16
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    maybe try underpowering? Tune the power supply to 4.9?

  7. #17
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Hello,

    Thanks for comments. I will try the lower voltage on the PSU and report back.

  8. #18
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Took me awhile to find this video from auschristmas (Keith). The very technical video from Keith is helpful. https://www.youtube.com/watch?v=1ebSWCo7sYQ.
    Hope this helps someone.

  9. #19
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    Update:

    Lowered the PSU to 4.91v (lowest it would go) = no difference to pixels at all.

    Wow - That video is packed full of useful technical detail, all good stuff. Watched it all but nothing relates directly and exactly to the issue I am having.


    WordSemi have stated that there should still be an external de-coupling 0.1uF capacitor on the WS2811 chips - The Ray Wu pixels do NOT have this capacitor and I now 100% sure this is the root cause of all my problems.

    Broke out the scope and started probing all over the place with a test set-up of 10x50 pixel strings, driven by Falcon F16v3:
    - Flickering / flashing is still not present at all when brightness is >70%, any colour for all 500 pixels. Flickering/flashing worst at around 24/255 brightness level, any colour.
    - Data signal integrity actually looks pretty good and pulses are certainly within specifications for timing and shape when checked every 50 pixels along the string.
    - No significant voltage drop present anywhere in the strings.
    - 5v power line is quite noisy. Around 300mV peak to peak ripple, but similar at start, throughout and end of 500 pixels. Is similar with no data and data being supplied to the string. (This power supply works fine with my other 1000 pixel, single string props).

    Tried adding 0.1uF capacitors at every string junction (between strings of 50) - made slight improvement (from the 1st 300 pixels not flashing to about the first 340-350 pixels not flashing at all. Remainder of strings all flash. 5v ripple reduced to around 150-200mV peak to peak (but measured at the same point as the added capacitor - no idea what the power line looks like in the middle of a 50 string (furthest point from a 0.1uF capacitors).

    Decided to cut all 10 strings every 25 pixels and add another 0.1uF capacitor - made no noticeable difference to flashing when compared to having capacitors every 50 pixels.

    This was a desperate attempt to mitigate the missing capacitors on the Ray Wu pixels. The de-coupling capacitors I added are just too infrequent and too far from the actual ws2811 chips to be effective. Without cutting every single pixel and adding a capacitor as close as I could, (and I doubt this would be close enough to each chip), I doubt I am going to find a solution.

    So in summary, the WorldSemi data sheet and WorldSemi themselves state that an external de-coupling 0.1uF capacitor is needed on their WS2811 chips. Ray wu pixels have been made with NO external 0.1uF capacitor on the chip. Ray Wu is not interested at all in helping to resolve the problem, despite providing videos of the problem, pictures of the pixels boards without capacitors and WordSemi specification/requirements . I have 2500 useless 5v pixels from Ray Wu (unless you want less than 250 pixels per string, per controller output).

    BEWARE: RAY WU 5v pixels are NOT made to the specifications laid down in the WS2811 manufacturers data sheet and WILL cause you no end of problems. They are JUNK. AVOID THEM.

    Thank you to everyone who has offered advice in this thread and tried to help me resolve this. Any suggestions for reputable sources of 2500 5v WS2811 pixels please?

    Kind regards,
    Steve

  10. #20
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    Default Re: WS2811 flicker but only at low brightness - Help please?

    FYI: EVERY pixel regenerates the data signal. This means that the longest data run is from one pixel to the next pixel in the chain. Put a bypass cap on the last pixel that is NOT flickering. This is the pixel generating the data that the first flickering pixel is having an issue with. Most likely the first flickering pixel is a victim of the pixel before it having an issue. Doing this you may find that it is only a few pixels that are having an issue.


    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

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