RGB led strips flicker with PCA9685

[vinuthgamage]

Hi guys,
l am quite a newbie to arduino and lately I have been messing around with SMD5050 rgb strips for my balcony fence. I have used exactly 13 strips, each strip being 0.3 m long. To control all the channels I used 3 PCA9685 chained and connected to 13 uln2003a IC and each strip was wired as follows:

previous problems I encountered were discussed in the following topics:

PCA9685 not working properly with arduino UNO

[image] Hi guys, I am quite a newbie to arduino and lately I have been needing to expand the number of pwm pins in the arduino board for one of my projects. So, I have used a PCA9685 module I bought online to do this. To test this board's capabilities I hooked it up to an led as shown in the diagram above. But it only worked when I connected the led to channel 0 of the board using the code, PCA9685.setPWM(0, 0, 4095); and the rest of the channels did not work. This is the exact board I used: …

PCA9685 how to get the duty cycles figured out for RGB

Hey everyone, I am new to arduino and recently I have been messing with some dumb arduino non-addressable strips. I am currently doing a project with them where I am trying to control 14 individual strips using pwm signals. For expanding the pwm outputs in the arduino I have used 3 PCA9685 boards chained together giving me 45 pwm outputs and as the driver to the LEDs I have used a couple of uln2003a modules connected to the PCA9685 boards. But to get a wider range of colors for these LEDs I have…

Using uln2003a ic with PCA9685 servo driver

Hi all I am quite new to arduino and lately I have been experimenting about led strip lights for arduino. I am currently doing a project where I need to control 14 rgb led strips that need 12V to operate. Since I need to control each of them individually I am planning to use uln2003a darlington array ICs to switch ground connections to the strips. But I will need 42 pwm pins from my arduino mega to control the strips. So I decided to chain 3 of PCA9685 servo motor drivers together. I want to kno…

Will software pwm be reliable in this project?

Hello everyone, I am quite new to arduino and new to the forum. I lately have been messing with these smd5050 (dumb/non-adressable) rgb strips. I decided to take on this project of making something like an animation thing using them for my balcony fence. I will be needing pwm outputs from the arduino to control each fo the led strips. But I will be needing 42 of these pwm outputs. I am using an arduino mega but the number of pwm pins it has is not enough. I was thinking of using software pwm to …

But due to all the help of the people in this forum I was able to solve them, So I really do appreciate it!

But I have tried to implement a fade animations for all the strips at once using the following code:

#include "Wire.h"
#include "Adafruit_PWMServoDriver.h"

int r, g, b;
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
Adafruit_PWMServoDriver pwm1 = Adafruit_PWMServoDriver(0x41, Wire);
Adafruit_PWMServoDriver pwm2 = Adafruit_PWMServoDriver(0x42, Wire);
void setup() {

  Wire.begin();
  pwm.begin();
  pwm.setPWMFreq(500);
  pwm1.begin();
  pwm1.setPWMFreq(500);
  pwm2.begin();
  pwm2.setPWMFreq(500);  
}

void colorFading(int F_DELAY) {
  for (r = 0; r < 4095; r+=1) {
  pwm.setPWM(0, 0, r);
  pwm.setPWM(3, 0, r);
  pwm.setPWM(6, 0, r);
  pwm.setPWM(9, 0, r);
  pwm.setPWM(12, 0, r);
  pwm.setPWM(15, 0, r);
  pwm1.setPWM(2, 0, r);
  pwm1.setPWM(5, 0, r);
  pwm1.setPWM(8, 0, r);
  pwm1.setPWM(11, 0, r);
  pwm1.setPWM(14, 0, r);
  pwm2.setPWM(1, 0, r);
  pwm2.setPWM(4, 0, r);
  }
  delay(F_DELAY);
  for (b = 4095; b > 0; b-=1) {
  pwm.setPWM(2, 0, b);
  pwm.setPWM(5, 0, b);
  pwm.setPWM(8, 0, b);
  pwm.setPWM(11, 0, b);
  pwm.setPWM(14, 0, b);
  pwm1.setPWM(1, 0, b);
  pwm1.setPWM(4, 0, b);
  pwm1.setPWM(7, 0, b);
  pwm1.setPWM(10, 0, b);
  pwm1.setPWM(13, 0, b);
  pwm2.setPWM(0, 0, b);
  pwm2.setPWM(3, 0, b);
  pwm2.setPWM(6, 0, b);
  
  }
  delay(F_DELAY);
  for (g = 0; g < 4095; g+=1) {
  pwm.setPWM(1, 0, g);
  pwm.setPWM(4, 0, g);
  pwm.setPWM(7, 0, g);
  pwm.setPWM(10, 0, g);
  pwm.setPWM(13, 0, g);
  pwm1.setPWM(0, 0, g);
  pwm1.setPWM(3, 0, g);
  pwm1.setPWM(6, 0, g);
  pwm1.setPWM(9, 0, g);
  pwm1.setPWM(12, 0, g);
  pwm1.setPWM(15, 0, g);
  pwm2.setPWM(2, 0, g);
  pwm2.setPWM(5, 0, g);
  }
  delay(F_DELAY);
  for (r = 4095; r > 0; r-=1) {
  pwm.setPWM(0, 0, r);
  pwm.setPWM(3, 0, r);
  pwm.setPWM(6, 0, r);
  pwm.setPWM(9, 0, r);
  pwm.setPWM(12, 0, r);
  pwm.setPWM(15, 0, r);
  pwm1.setPWM(2, 0, r);
  pwm1.setPWM(5, 0, r);
  pwm1.setPWM(8, 0, r);
  pwm1.setPWM(11, 0, r);
  pwm1.setPWM(14, 0, r);
  pwm2.setPWM(1, 0, r);
  pwm2.setPWM(4, 0, r);
  }
  delay(F_DELAY);
  for (b = 0; b < 4095; b+=1) {
  pwm.setPWM(2, 0, b);
  pwm.setPWM(5, 0, b);
  pwm.setPWM(8, 0, b);
  pwm.setPWM(11, 0, b);
  pwm.setPWM(14, 0, b);
  pwm1.setPWM(1, 0, b);
  pwm1.setPWM(4, 0, b);
  pwm1.setPWM(7, 0, b);
  pwm1.setPWM(10, 0, b);
  pwm1.setPWM(13, 0, b);
  pwm2.setPWM(0, 0, b);
  pwm2.setPWM(3, 0, b);
  pwm2.setPWM(6, 0, b);
  }
  delay(F_DELAY);
  for (g = 4095; g > 0; g-=1) {
  pwm.setPWM(1, 0, g);
  pwm.setPWM(4, 0, g);
  pwm.setPWM(7, 0, g);
  pwm.setPWM(10, 0, g);
  pwm.setPWM(13, 0, g);
  pwm1.setPWM(0, 0, g);
  pwm1.setPWM(3, 0, g);
  pwm1.setPWM(6, 0, g);
  pwm1.setPWM(9, 0, g);
  pwm1.setPWM(12, 0, g);
  pwm1.setPWM(15, 0, g);
  pwm2.setPWM(2, 0, g);
  pwm2.setPWM(5, 0, g);
  }
  delay(F_DELAY);
}
void loop() {
 colorFading(10);

}

The animations seem smooth but the problem is that when the fade happens the strips flicker and this is specially visible in the last few led strips connected to the third PCA9685 board. If anyone has their ideas, I would appreciate you guys very much if you can share them.

[UKHeliBob]

@vinuthgamage

this is specially visible in the last few led strips connected to the third PCA9685 board. If anyone has their ideas, I would appreciate you guys very much if you can share them.

This has surely been suggested in one or more of your other topics on your project, but have you tried providing power to both ends of your LED strips rather than just at one end ?

[vinuthgamage]

hi Mr. UKHeliBob. thanks for the response but how will that help this problem

[xfpd]

Power sags as it travels down a conductor (conductors have resistance, reducing the voltage, V = IR). "Injecting" power at multiple locations along the LED strip allows the LEDs to have full VCC rather than the sagging voltage.

[vinuthgamage]

But I do not think that really this is the problem since it works just fine when fading effect is not used or when fading effect is only used on one or two channels without using it on all chanels...

[xfpd]

@vinuthgamage

I do not think that really this is the problem

Why not? Why do you think resistance is not present in every wire?

How many LEDs are involved? How many in each channel? What is the size of the power supply?

@vinuthgamage

the strips flicker

PWM is "flickering".... and if you add resistance, the LEDs going OFF to ON to OFF will show that flickering.

@vinuthgamage

fading

An LED with increased resistance is "faded"

[SurferTim]

The PCA9685 has 200 ohm resistors on the signal outputs. Maybe that has an effect.

[vinuthgamage]

Ah ok thanks for the clarification. Well I am using smd5050 nonaddressable dumb rgb led strips and as the power supply I am using a 12v car battery.

[vinuthgamage]

Hi Mr SurferTim, thanks for the response. Yes this can also be the problem.

[xfpd]

@vinuthgamage

nonaddressable dumb rgb led strips

Monochrome LED strips still have resistance in their wires.

[vinuthgamage]

How to avoid PCA9685 flickering at high values when LEDn_ON > 0

Do you think this can be a the problem as well. Maybe I should use the library these peopl use and try it out.

[xfpd]

I do not know. Give it a try.

[vinuthgamage]

#include "PCA9685.h"

PCA9685 pwmController1(B000000);        // Library using B000000 (A5-A0) i2c address, and default Wire @400kHz
PCA9685 pwmController2(B000001);        // Library using B000001 (A5-A0) i2c address, and default Wire @400kHz

// Not a real device, will act as a proxy to pwmController1 and pwmController2, using all-call i2c address 0xE0, and default Wire @400kHz
PCA9685 pwmControllerAll(PCA9685_I2C_DEF_ALLCALL_PROXYADR);

void setup() {
    Serial.begin(115200);               // Begin Serial and Wire interfaces
    Wire.begin();

    pwmControllerAll.resetDevices();    // Resets all PCA9685 devices on i2c line

    pwmController1.init();              // Initializes first module using default totem-pole driver mode, and default disabled phase balancer
    pwmController2.init();              // Initializes second module using default totem-pole driver mode, and default disabled phase balancer

    pwmControllerAll.initAsProxyAddresser(); // Initializes 'fake' module as all-call proxy addresser

    // Enables all-call support to module from 'fake' all-call proxy addresser
    pwmController1.enableAllCallAddress(pwmControllerAll.getI2CAddress());
    pwmController2.enableAllCallAddress(pwmControllerAll.getI2CAddress()); // On both

    pwmController1.setChannelOff(0);    // Turn channel 0 off
    pwmController2.setChannelOff(0);    // On both

    pwmControllerAll.setChannelPWM(0, 4096); // Enables full on on both pwmController1 and pwmController2

    Serial.println(pwmController1.getChannelPWM(0)); // Should output 4096
    Serial.println(pwmController2.getChannelPWM(0)); // Should also output 4096

    // Note: Various parts of functionality of the proxy class instance are actually
    // disabled - typically anything that involves a read command being issued.
}

void loop() {
}

guys I wrote this code to test out some other abilities of this library but it does not out 4096 and 4096 in serial monitor.

[SurferTim]

It is 12 bit resolution. That is 0 to 4095. 4096 is the 13th bit.

[vinuthgamage]

I tried putting 4095 aswell but still does not work.

[SurferTim]

I've seen this before. Try setting an int variable to 0 and 4095 and use the variable in the calls. It had problems using a literal number. Don't know why.

[vinuthgamage]

Ok let me try, can you confirm my idea about what this program does btw by explaining what it does to me.

[vinuthgamage]

I was thinking it will set the given value to channel 0 in all boards.

[UKHeliBob]

@vinuthgamage

this program

Which program ?