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I am totally desperate and hope you can help me. I've been building a project for a while where I have to control several servos. For this I bought some MG996R servos and a PCA9685 16-Channel Servo Driver board. Furthermore, I bought a suitable power supply (DV 5V - max 3A).

First, I connected my controller and the board as follows and attached the power supply at the intended place: enter image description here

Everything worked as desired and I could control e.g. one servo with this example script.

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>

Adafruit_PWMServoDriver myServos = Adafruit_PWMServoDriver();

#define SERVOMIN  150
#define SERVOMAX  600

uint8_t servonum = 0;
uint8_t numberOfServos =  1;

void setup() {
  myServos.begin();
  myServos.setPWMFreq(60);
  delay(10);
}

void loop() {
  myServos.setPWM(0, 0, 500);
  delay(1000);
  myServos.setPWM(0, 0, 300);
  delay(1000);
}

Then I tried something and reconnected a few cables while the power supply was still on (my bad) - after that no servo moved with the original setup (see picture above). After that I tried to find the broken part but couldn't find any - so I bought a new Arduino, PCA board and power supply to try and find the error - unfortunately without success.

Then I found out by chance that the servos move again when I connect the ground of the external power supply to the Arduino and plug the positive pole of the power supply to the V+ with the PCA9685. That is, enter image description here

I ordered a pack of three new PCA9685s and again same problem - the servos no longer move when using the designated place for the power supply on the PCA9685 board - what is going on? Can anyone explain this and help me where the problem is?

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  • measure voltage at arduino
    – Abel
    Commented Nov 20, 2021 at 15:57
  • what are your thoughts? what voltage should I measure?
    – Ai4l2s
    Commented Nov 20, 2021 at 17:05
  • power for arduino as you run motors, in each the working and failing configurations. there are only 4 or 5 leads, at least one of which is ground so you could just measure everything one at a time and see the difference.
    – Abel
    Commented Nov 20, 2021 at 21:42

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