Problem with weld led strip

Hi everyone,

I have a problem with a led strip, I want to cut it in 3 pieces and weld them together with electric wire and put them in one of my shelf, so I weld them together and fix the weld with my glue gun, with that I'm sure that none of my weld will break and it work fine and all the led are lighting up I use a very basic code that just light up the led in white color. (I use this strip because it's an extra from a previous project)

but, here's my problem, the last strip just don't light up when I turn on the whole set, but, the strange thing here and the reason why I'm writing here is: when I hit the strip with my finger it just light up but with some very random and unwanted effect (some led light up and other just don't, they sometimes light up with a bad color) and when I hit it again the effect change. and when I update my code via Arduino the first 2 strip are updated correctly but the last one just don't do anything.

I don't think it's because of my welding because the led are lighting up good (they don't blink or anything) but it can be a part of the problem, I'm not a pro in this domain.

Maybe the strip is just broke and there is nothing to do but I want to search for a solution first.

Do you know if there is a way to put back this rebel strip into the right path?

Thank You.

Check the data line. If the power lines are good but the data line has a bad connection it could cause the issue because they're getting power but not clean control signals.

Did you use a TIG or a MIG welder?

What temperature is your glue gun set at?

Put your ear at the end of the strip when you first turn it on. What do you hear?

Thanks for your answer.

Pert : how can I check that? I’m a beginner in programing with Arduino.

Boolrules : I use the classical duo: soldering iron and some tin. I use a very old glue gun there’s no control of the temperature.

If they are addressable RGB also check which way round the data line is on the "bad" strip.

Done that trick myself and spent over an hour trying to figure it out.

How can I do that? I'm pretty sure that the bad strip can work good because when I first weld them together, I made some test just by connecting my arduino card and all the strip were lighting up correcty, the problem happen after that. just before I use the glue gun to fix the last weld (which is not the weld on the last strip but the weld on the second one to connect the wire who lead to the bad strip).

There is usually a small arrow on the data line near the cut points that shows the direction towards the END.
Make sure that is pointing AWAY from the arduino.

Yep it's pointing in the right direction.

Maybe post the sketch you are using for the strip in case it is a simple error in there ?

Or there is a bad connection.

here it is.

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
  #include <avr/power.h>

#define PIN            6

#define NUMPIXELS      150

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

 int delayval = 10; 

void setup() {

void loop() {

  for(int i=0;i<43;i++){

    pixels.setPixelColor(i, pixels.Color(50,50,50));; 

  for(int i=43;i<NUMPIXELS;i++){

    pixels.setPixelColor(i, pixels.Color(50,50,50));; 


I dfont have my neopixels to check right now but looking here

for(int i=43;i<NUMPIXELS;i++){

is that 43 correct ?

My bad if I am wrong.

What is the difference between:-

for(int i=0;i<43;i++){
    pixels.setPixelColor(i, pixels.Color(50,50,50));;
  for(int i=43;i<NUMPIXELS;i++){
    pixels.setPixelColor(i, pixels.Color(50,50,50));;


for(int i=0;i<NUMPIXELS;i++){
    pixels.setPixelColor(i, pixels.Color(50,50,50));;

And anyway should it not be:-

for(int i=0;i<NUMPIXELS;i++){
    pixels.setPixelColor(i, pixels.Color(50,50,50));

yes! normally it's 0, but I made some test to light up the strips with different color and I forgot to put it back to 0 before copy and paste it.

Grumpy_Mike : With the one I send the leds are lighting up one after another, with your solution all the leds lights up at the same time, the results is the same but with the one I use it add a little “animation” when I turn on the strips.

If that is your intention then fine. If you add avert small delay before each show then it becomes more pronounced.

However I would say that your origional problem is faulty wiring.