Hi, I have 8 WS2812B strips connected in series like this:
Teensy 3.2 > MAX485 transmitter board > MAX485 receiver > 60 LED long WS2812b LED strip > MAX485 transmitter > MAX485 receiver > 60 LED long WS2812b LED strip > MAX485 transmitter > and so forth (8 strips in total)
Each strip has it's own power source (5v 4A).
The problem I have is this: the first strips work well, but they're increasingly noisy as the chain advances. When there are few pixels lit the entire system works flawlessly, also works great when I light them all for just one frame and then go to black (like a flash). The problem appears when there's a lot of pixels lit with the same color and increases with brightness.
EXAMPLES OF THE PROBLEM (the structures are daisy chained from right to left):
THINGS I TESTED
Lack of power: every structure has it's own power source (a 5v 4A switching power supply, the structures consume a maximum of 5v 3.7A, but I wasn't near this on the examples I showed), I thought the problem could be related to lack of power, I tested two structures with one common power source of 5v 35A, the problem worsened (so it seems it is somehow related to the power source). And also, looking at the videos you can notice that the problem is worse in relation to the number and brightness of the LEDs.
GND problems: I've read that some projects with similar problems solved it by making changes in the way the GND is wired. I did some tests: using one common power source, cutting the common ground, etc. The problem was always the same no matter what I did with the GND wires.
Design of the MAX485 boards: the design of these boards is based on this one. I know that the signal is transmitted and received correctly because of the examples you can see on the videos marked as not having problems. I would like to find a solution that doesn't make me replace these boards.
Signal reflection: lastly, my last hope was signal reflection. It happens that in some patterns, when they don't work, you can see some noisy "inverted" pattern elements. For example, mixing the pattern shown in the "small cyan" videos with a solid background, sometimes a yellow same sized pattern appears on some structures (I understand yellow as having the inverted signal of cyan, inverted in time not in color, you can se something like this in the "big cyan section" video). I tried removing the last MAX485 transmitter (that sends signal into open wires) thinking it could be the problem, but after removing it the problem is the same. You think it could be signal reflection? Should I put diodes at the end of the last strip dataline?
Some extra info: solid colors like green, blue and red work fairly well (little noise at the end of the chain), the problem is more present when I mix two colors (cyan, magenta and yellow). White works better.
Thank you in advance, I hope someone finds this problem pretty obvious and can give me hand.