Long Run to First WS2811 Addressable LED in a Strand. Requires WS2811 as Repeater

[marksy95]

I have a string of what used to be 100 bullet WS2811 LEDs (these to be exact Amazon.com) that I've now cut down to 24 after mounting in a 2x2. I've got them working with a 10" pigtail connector:

They seem to work ok when I just use the 10" pigtails, but I've extended the 10" pigtails into a 16.5' cable to run from the wall to my desk and it's not working correctly any more. The wiring is identical and the only thing that changes is the length of the pigtail.

I've checked resistance of each conductor (0.1 - 0.2 ohms) and I've checked for shorts. Everything checks out.

You can see red is power, black/white/blue is ground, and yellow is data. The Arduino is grounded to the 12V power supply ground (10A power supply for the LEDs). I have a 470 ohm resistor on the data line as recommended by Adafruit.
10" pigtail:

16.5' cable:

Using an Elegoo Uno R3 (Amazon.com)
The Arduino program was not changed between swapping the cables.

#include <Adafruit_NeoPixel.h>
Adafruit_NeoPixel strip(24, 3, NEO_RGB + NEO_KHZ800);

void setup() {
  strip.begin();
  strip.clear();
  strip.setBrightness(155);
}

void loop() {
  for (int i =0; i < 24; i++)
  {
    strip.setPixelColor(i, strip.Color(0,0,255));
  }
  strip.show();
}

Do I need a data repeater/amplifier for the WS2811?

[er_name_not_found]

The power can drop off, you may need to power the strip in a few places, you may also need a larger power supply.
How many LEDs are there in your 16.5' cable?

[marksy95]

I think you misunderstood what the 16.5' cable is. The 16.5' is the new pigtail length. There are no
LEDs in that length. It only carries power to the strip and signal to the first LED.

I checked voltage at the Wago's pictured (right before the strip); it's 12.2V. These LEDs are rated at 0.24 W (0.6 W max) each. Its a 12V/10A power supply, so 120 W. 0.6 * 24 = 14.4 W max. There should be no issues with power delivery.

[er_name_not_found]

Indeed I did. My mistake.
Do you have a decoupling capacitor at the beginning of the string of LEDs?

[er_name_not_found]

Also, data cable length is discussed in this article: Maximum length data wire LEDs (ws2812b, sk6812, ws2815) - quinled.info

[marksy95]

I do not. Is that the one that would go in parallel with the power source and LEDs?
Looks like I might need to use anoter WS2811 as a repeater:

Adafruit NeoPixel Überguide

• Try to minimize the distance between the Arduino and first pixel, so the signal is clear. A meter or two is usually no problem. Much longer and things can become unreliable. Individual NeoPixels can act as repeaters for long runs.

[marksy95]

I have resolved the issue. I did, in fact need to use WS2811s repeaters. I ended up putting 3 LEDs ~4' apart on the 16.5' cable. I am using these as repeaters only, so the code looks like this now:

#include <Adafruit_NeoPixel.h>
#define NUM_PIXELS 24
#define NUM_REPEATERS 3
#define LED_PIN 3
Adafruit_NeoPixel lights((NUM_PIXELS + NUM_REPEATERS), LED_PIN, NEO_RGB + NEO_KHZ800);

void setup() {
  lights.begin();
  lights.setBrightness(100); // x/255
  lights.clear();
}

void loop() {
  for (int i = NUM_REPEATERS; i < (NUM_PIXELS + NUM_REPEATERS); i++)
  {
    strip.setPixelColor(i, strip.Color(0,0,255));
  }
  strip.show();
}

[er_name_not_found]

Cool, thanks for providing the follow-up. It will help others in the future.

[marksy95]

That's the goal. I'm sure I'm not the only one who's run into this and now next time someone does (if they find this), they'll have a definite answer.

[Deva_Rishi]

Ok well i've explained the cause before on this forum. And the cause is capacitance of the cable. The capacitance of the cable is distorting the signal. The longer the cable or the thicker the data cable, the more capacitance.
You have found 'a' solution, there are more. You can instead of using LED chips, use a 7400 series TTL chip in the cable like running the signal 2x thru a not gate of a 74HCT04 or 74HCT14 IC works. Of course if you are using 12v strip you would need a 5v regulator as well.
Thinner cable may also help really quite a lot, but my favorite solution is using 2x MAX485 transceivers and a twisted pair cable. This also allows for a separate power supply without any issue.