LED strip command only works if connected to PC

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1

Hi everyone! Here's my issue : I'm using an arduino uno R3 to command an LED strip. The LED strip is powered in 24V on its own, and the arduino is powered in 12V separately. The arduino GND and the LEDs GND are connected, and i'm using pin6 in output pull down mode connected to the signal line of the LED strip. No resistors, no capacitors, since the LED strip has controllers and resistors every 6 LEDs.
It worked perfectly connected through USB, and through the jack too for a while. But after 2h, nothing worked and the L LED stays on and looses intensity when i touch the metal casing of the USB port. Until I powered it through the USB and everything works fine.

I checked the 5V and 3.3V outputs and they're fine so i'm at a loss... Can someone help me?

2

Tu be sure, can You draw and post a hand drawn schematics showing the troubelling setup?

3

There is no "output pull down mode", there is only "OUTPUT" mode.

4

Install resistor (470R from Arduino DIO to LED DIN) and electrolytic capacitor (power to ground) to protect your Arduino.

You compiled for something other than Uno R3 because OUTPUT_PULLDOWN does not exist for the Uno R3. Was this pulldown external?

C:\Users\user\AppData\Local\Temp\.arduinoIDE-unsaved202561-20368-s42o4f.e7jfq\sketch_jul1a\sketch_jul1a.ino: In function 'void setup()':
C:\Users\user\AppData\Local\Temp\.arduinoIDE-unsaved202561-20368-s42o4f.e7jfq\sketch_jul1a\sketch_jul1a.ino:4:19: error: 'OUTPUT_PULLDOWN' was not declared in this scope
   pinMode(LEDPIN, OUTPUT_PULLDOWN);
                   ^~~~~~~~~~~~~~~
C:\Users\user\AppData\Local\Temp\.arduinoIDE-unsaved202561-20368-s42o4f.e7jfq\sketch_jul1a\sketch_jul1a.ino:4:19: note: suggested alternative: 'INPUT_PULLUP'
   pinMode(LEDPIN, OUTPUT_PULLDOWN);
                   ^~~~~~~~~~~~~~~
                   INPUT_PULLUP
exit status 1

Compilation error: 'OUTPUT_PULLDOWN' was not declared in this scope

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