Weird but easy way to get super long runs of data cable from OctoWS2811

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Weird but easy way to get super long runs of data cable from OctoWS2811 board to WS2812b LEDs… what gives?!?

I also posted this in the pjrc forum, but thought you might be interested…

I tried to connect a string of 2m of WS2812b LEDS (two 1m sections of 144 leds/m) to an OctoWS2811 adaptor board via a roughly 20m length of CAT5e cable (for data - power is local to the string, ground is looped back to the Octo) and (sort of as expected) it didn’t work (sparkly / flashy Bad Things ™ happening).

But here is the really interesting part… if I put that cable between the two 1m sections of WS2812, then it worked fine. In fact, I’ve tried up to 55m (180 feet) of cable without the slightest problem (to be really silly, I even mixed the UTP and some lightweight figure 8 speaker cable!). To be clear, configuration is:

OctoWS2811 adaptor -> 1m WS2812 strip -> 55m (180 feet) CAT5e & fig 8 speaker cable -> 1m WS2812 strip

Power supplies local to the strips, common ground (0v) cable joining all entities. Voltage input measured at each strip is about 5.05v (uncalibrated cheapie DMM).

This has worked for several hours so far without the slightest glitch.

Has anyone else ever tried this?

Next thing to try - single LED adjacent to the Octo, and use that as a ‘long line’ driver. Also longer lengths of cabling, and driving multiple strips down a single UTP cable.

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Yep, I’ve heard of people doing this before. The LED driver chips put out a cleaner signal than your OctoWS2811 adapter, so put single LED’s at the output of the board and every so often to act as repeaters on long runs.

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you need to use a “null pixel”.
Also, check the voltage at the start and end of your strip.

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@Stuart_Taylor Thanks for the reply! Voltage is rock solid 5.05v at both ends of both strips (I run a beefy parallel power bus).

When you say I need to use a “null pixel” - do you mean a single pixel adjacent to the Octo, which then drives the long run to the rest of the strips? If so, this is in the ‘next thing to try’ basket.

Main reason I wrote this is that I’ve seen lots of people asking how to drive long cable lengths between the Octo adaptor and their LED strings, and the common answer seems to be some sort of additional line driver (ie a differential RS485 transmitter/receiver pair). This is rather a bit over-engineered if all it takes is one pixel local to your Octo…

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I have run 15-30m segments of cat5e from the octows2811 adapter to ws2812’s without any problems. I just make sure that grounds are shared everywhere.