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() {

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

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?

  • 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


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.