About driving LEDs over long distances ey community! I am facing some challenges when

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About driving LEDs over long distances

ey community!

I am facing some challenges when it is about driving Led strips over long distances. By experience I have got to know that the cable normally used to drive Led strips (22AWG) is not good anymore if it is longer that 10 meters.

I realized this while working with 5 pieces of 2 meters of WS2812b where all of them are several meters apart from the Arduino board that I use to control them. In that case, I was sending the same program to all of them, and what I did was to connect all of them to the same pin, and it didnt work at all. The sum of the lenght of all 10 cables was much longer than 10 meters, and the signal got lost.

While searching for a solution, I discovered a post by Teknynja (https://goo.gl/eOaU1U) where it is explained how to use SN75176 to be able to drive WS2812b on cables much longer than 10 meters. I did the experiment myself, and even though he uses CAT 5 cable, I was able to succesfully send signal over 50 meters of 22AWG cable.

After that, I used SN75176 not to use longer cables, but to split the signal from the output pin into 5, and then I could connect 22AWG cable to drive each piece of led strip apart from the board some 10 meters each. (images of the board at the bottom of the post)

so far, so good.

Now I was trying to drive 4 pieces of 2 meters of WS2812b that are some 8 meters away from the arduino board, and again they are all displaying the same program out of a single arduino pin. So I connected a 8 meters long 22AWG cable to the arduino, which is inside of the restraints previously mentioned, and at the end of this cable I connected one of my “splitter board”, to send the signal to the 4 Led strips. It didnt work.

I have the feeling that the SN75176 do the job only if it is connected close from the arduino board, but if there is already a lenght of cable between the pin and the driver (SN75176) the signal is already weak enough or noisy enough for the SN75176 to manipulate it properly.

I of course did a lot of try outs in different circumstances, different cables, lengths and a large list of etceteras, but I dont think it is worthy to post them here. Perhaps with the information already provided, some of you already has an idea on how to sort out these problems. How do you drive ws2812b over long distances?

I appreciate very much your interaction.

:smiley:

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Leo, the primary reason for 22AWG wire is for the power. Where the signal wire is for speed… I would suggest that you try your driver/splitter with the twisted pair wire on the DI strip pin and ground. Terminate this with a 10K pull-up and about 1000uF capacitor at each strip power terminals… signal line capacitance is the killer… have fun. :slight_smile:

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Leo, welcome to the mysterious world of data bus termination. You might remember that some sources suggest a resistor in series of the data line. This is not to limit current but acts as a source termination resistor.
Good link to understand the problem: https://electronics.stackexchange.com/questions/171557/what-and-whys-of-termination
When you search for more information you will find a myriad of explanations and formulas but you might wanna try a practical advice: The expected resistance will be somewhere between 25 and 150 Ohms. Take a 220 Ohm pot in series with your data line(s) and try your luck.

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Thank you guys for sharing! Until thursday I am away from home unable to try out things, but I will be readign and happy to receive opinions on the issue!

so much to learn!

there have been some other answer on https://electronics.stackexchange.com/questions/307664/about-driving-leds-over-long-distances