Help with WS2811 Data Signal Over Long Distance Using Falcon Pi HAT and MAX485

[rrfuglsby]

Hey everyone,

I'm running into a problem with my WS2811 LED setup. I'm using a Falcon Pi HAT on a Raspberry Pi to control one strand of 650 LEDs, and it did work UNTIL I had to extend the data wire from the pi hat to the first LED about 30 feet.

So what i did to fix the problem was to use two MAX485 modules (one as a transmitter and one as a receiver) over shielded CAT6 cable. I've got power and ground connected properly, the A/B differential lines match (A→A, B→B), and I'm powering both boards at 5V. The DE pin on the transmitter is tied high, and the RE pin on the receiver is tied low. Everything seems wired correctly, but the LEDs either stay solid or flicker randomly, and they're not responding to the data properly.

To be clear, the data wire comes out of the Falcon Pi Hat Output #1, it goes to the DI pin on the Max485 transmitter board, comes out of the A&B ports of the  Max485 transmitter board  using shielded Cat6 cable (about 30 feet), connects to the Max485 receiver board on the respective A&B ports, goes out of the RO pin on the Max485 transmitter board, and finally gets to the first led.

It really seems like a data signal integrity issue, but I'm not sure how to fix it. Has anyone successfully used MAX485 boards to extend WS2811 data? Any advice or wiring checks I should try would be appreciated! 

Thanks!

[jnealand]

How does the cost of two MAX485 compare to the cost of another Pi?  Sounds like it might be a lot simpler to put a 2nd Pi in place and use FPP master remote to keep them in sync.

[JonD]

How long of a distance are we talking?

Have you considered a F-Amp to boost the data signal?

https://pixelcontroller.com/store/accessories/55-famp-raywu.html

[rrfuglsby]

Thanks for the replies. To give more context:

Unfortunately to my bad planning, the position of the first LED is NOT in a good location to keep a controller. I initially had it there, but to get there for any maintenance reasons is a nightmare. The sd card on the pi got corrupted after the circuit breaker tripped, so I thought it would be a good opportunity to move it to a better location. The distance between the first LED and the controller now is 30 feet.

I saw that F-amp product before but none of my current connections use pigtails so I didn't think i should/could use that (but I'm a newbie when it comes to this). I also didn't want to use the rj45 port on the falcon pi hat because x-lights gives this error when I tried to add the strand: "ERR: Serial port 1 has 1950 channels allocated but maximum is 512.". The two MAX485 boards are actually really cheap. I already bought them and wired them in so I was hoping I could get them working but I am getting nervous now.

  Thanks!

[k6ccc]

30 feet is almost certainly your problem.  As far a pigtails, most of mine don't either, but it's easy enough to solder an F-Amp in the middle of the line...

[rrfuglsby]

But RS485 communication has a theoretical maximum of around 3900 feet so i thought it would be fine.

[k6ccc]

RS-485 can go 4K feet, but pixel string do not use RS-485.

[rrfuglsby]

The signal from the controller IMMEDIATELY goes into a MAX485 board that converts the signal to RS485. Then it goes 30 feet, has a MAX485 boards that converts it BACK to the original data signal and FINALLY goes to the first LED.

[k6ccc]

Sorry, I read the first part of your original paragraph to mean that you speculated that using the MAX485 boards would be a solution - not that you were doing it that way.

Can't help you as I have no knowledge about MAX485 boards.

[JonD]

30ft can be okay, but conditions have to be right.   12v goes farther than 5v, different lights go further than others.  I have a few 55ft extensions and get a long fine, but know I am pushing my luck.  If it works great, if not, you will have to fix it.

You want to use 18 gauge wiring.  Thinner is better for data, thicker is better for power, 18 AWG is the sweet spot.  Some people use CAT6 wire to feed the lights, and it can work, but it is not ideal.  18 AWG is best.  The F-Amp is going to take the signal and clean it up and send it on.  This may help the problem.   They offer plain versions as well.

https://pixelcontroller.com/store/accessories/53-famp.html