I have a problem with my NodeMCU v2 board and my WS2812B led matrix with 256 (32x8) LEDs.

The Board cannot be able to turn on the 191th led and stops working after the 190th without changing the color of the rest of the strip.

I'm using an external power supply 5V 20A and the strip is connected as shown below


I tested the problem with the FastLED library.

#include <Arduino.h>
#include <FastLED.h>
#define NUM_LEDS 256
#define DATA_PIN 2


void setup() {
  FastLED.addLeds<NEOPIXEL, DATA_PIN>(leds, NUM_LEDS);

void loop() {
  for(int dot = 0; dot < NUM_LEDS; dot++) {
      leds[dot] = CRGB::Red;
  for(int dot = 0; dot < NUM_LEDS; dot++) {
      leds[dot] = CRGB::Black;

The result is this

sad problem

How I can solve this?

  • possibly a bad LED
    – jsotola
    Oct 21, 2019 at 2:33
  • 1
    do not run power for the LEDs through the breadboard
    – jsotola
    Oct 21, 2019 at 3:11
  • The LED 5V is directly connected to the PSU without passing through the breadboard. Looks like that LED is not the trouble because It works fine with an Arduino Uno.
    – Gianlo
    Oct 21, 2019 at 9:07
  • power connections involve two wires ...the GND wire is shown as being routed through the breadboard
    – jsotola
    Oct 21, 2019 at 14:43
  • sometimes i have to run the esp at 3.5 or 3.6v (instead of 3.3v) to get them perfect
    – dandavis
    Oct 21, 2019 at 21:27


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