12V LED strips w/ Nano - power pulse/flickering issue

[alfermannw]

Hello,

I have an issue with my arduino nano beginning to pulse after a few seconds after triggering my 4 pwm outputs at full power (255). The pwm signals are going through TIP120's to regulate the current flow to ground for a 12V led strip. I have one strip with R, G, and B connected to pins 9, 10, and 11. I have the other attached to 6, and have the RGB pins on that strip all bridged together (illuminates white). My issue, is when I power them up, the lights stay on with the 12v supply to Vin/Gnd but then after a few seconds they begin to reset/pulse. I then plug in the usb connection to my computer and the issue goes away. My supply is a 12v 5A constant voltage supply. I tried adding 0.1 uF and 4.7uF capacitor across Vin/Gnd but that didn't help it. If I back down the pwm output to 200, then the issue takes much longer to occur (20ish seconds). once the issue starts, I can stop the flashing by plugging in the USB connection, but as soon as I unplug it begins again.

Any thoughts as to my issue? Thank you!

[alfermannw]

I monitored current during the flashing and it is dropping from 1.1A during normal operation all the way down to .5A during a flash. what could be causing this flashing to appear after 20-30 seconds?

[red_car]

Need:

• your code
• your circuit schematic

[alfermannw]

#include <stdio.h>
#include <stdlib.h>

#define white 6
#define red 9
#define blue 10
#define green 11

int brightness = 200;

void setup() {
  pinMode(red, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(white, OUTPUT);

  analogWrite(red, brightness);
  analogWrite(green, brightness);
  analogWrite(blue, brightness);
  analogWrite(white, brightness);
  
}

void loop() {
  
  
}

[alfermannw]

this in a nutshell granted I'm using pins 6, 9, 10, and 11.

[dlloyd]

Take another look in that nutshell, perhaps the base resistors are hiding in there.

[alfermannw]

good golly you were right! it was pulling too much power without resistors and was heating up the main chip really bad! I added 1.5k resistors between the base and pwm pins and that solved my flickering issue. thank you so so much!

[Paul_B]

So what was critically missing was the explanation in the OP that he was using some unspecified transistors - presumably rubbish TIP121s - instead of modern FETs!