Degraded data quality on long strings, perhaps Max485?

Troubleshooting
1

What am I overlooking and has anyone used a Max485 pair with a Pixelblaze? I am looking at

The setup:
I have 12 long strands of ~250-380 Pixels of SK6812 GRBWW that are roughly 3m-8m away from the PBv3 regular and output expander boards. The signal and 12V power is carried through cat6. Of the 12 strips, about 4 are showing some “artifacts” where they will not always show the right color (often with a blue or white flicker). The output expander already has a 100 Ohm terminating resistor at the start of the signal and each strip has a high-quality capacitor from 12V to ground between the cat6 and the strip. I have looked at adding a resistor at the strip end but my oscilloscope shows no improvement in the signal. Using the 'scope on the strips with artifacts shows signs of 60Hz induction on the line. The cat6 is 100 Ohm impedance.
For a 485 chip, I’m looking at https://www.amazon.com/Gumps-grocery-MAX485CPA-MAX485-Transceiver/dp/B082182H7H or these Amazon.com
Does anyone have experience that can help? Do I leave the resistor on the output expander?

2

I think that would work fine. I’ve used similar and the signal over cat5 is much better, as expected. There are RS485/RS422 breakouts too. You need one on each end (most are full duplex, but you only need 1 TX and 1 RX). You’ll need 5V on the receiving side, perhaps with a small buck converter.

Keep an eye out for lower bandwidth transceiver. 2.5MHz is fine, but you might have issues with something lower, and I’d be worried that even a 1MHz bandwidth would do justice to the variable pulse width LED data. It’s 800Kbps, but the short pulses are about 250ns / 2MHz wide.

If you add these, the resistor on the output expander isn’t going to hurt anything, the transmitter input won’t care.

3

I did check and the chips are good to 2.5MHz.
What do you mean by an RS485/RS422 breakout? Could you link to an example?

4

Like these

5

For posterity, I found that those chips do work well with a 5V buck converter, and likely a 5V linear regulator would work well too. My tests were for a protected but damp outdoor installation and the circuit needed to be waterproofed in a way that does not overheat in summer.
HOWEVER, I found that replacing connectors on the poor connection strips with good solder and marine heat shrink with glue works well and solves the problem in a more robust way. Score 1 for taking the time to get your basics right before messing with complicated solutions.

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