I am encountering an issue where the servos connected to the board are not receiving power from the external power supply, despite extensive troubleshooting.
Here's a summary of my setup and the diagnostic steps I've already performed:
My Setup:
Microcontroller: Arduino Uno
Servo Driver: PCA9685 16-Channel Servo Motor Driver
External Power Supply: "5V DC 2A wall adapter"
Connections:
Arduino Uno 5V to PCA9685 VCC
Arduino Uno GND to PCA9685 GND (logic)
Arduino Uno A4 (SDA) to PCA9685 SDA
Arduino Uno A5 (SCL) to PCA9685 SCL
External Power Supply Positive (+) to PCA9685 V+ **** terminal
External Power Supply Negative (-) to PCA9685 GND **** terminal
Troubleshooting Performed & Results:
I2C Communication Test: I ran an I2C scanner sketch on the Arduino. The PCA9685 board is successfully detected at address 0x40. This confirms that the PCA9685 chip is functional and communicating with the Arduino.
External Power Supply Verification: I directly measured the output of my external 5V power supply with a multimeter (disconnected from the PCA9685). It consistently provides 5.0V.
Servo Operation with Arduino Power (Diagnostic): As a diagnostic step, I temporarily connected the 5V from the Arduino Uno directly to the PCA9685's V+ power rail (bypassing the external supply connection). In this configuration, the servos moved and operated correctly with the code. This confirms that the servos themselves are functional, the PCA9685 board's internal power distribution (when supplied), and the control signals from the Arduino are all working.
Voltage Measurement at PCA9685 Servo Power Rail (with external supply connected):
voltage between the V+ and GND pins on the individual servo output headers (e.g., Channel 0's V+ and GND pins). The reading was consistently "0.50V".
Voltage Measurement with External Power Disconnected: Even after completely disconnecting the external power supply from the PCA9685's V+ terminal, the servo output pins still showed approximately 0.50V, indicating that the external 5V is not reaching this rail.
Conclusion:
Based on these tests, it appears that the 5V from the external power supply is not being properly passed through or distributed by the PCA9685 board from its V+ input terminal to the servo output V+ pins. Since the board functions when supplied directly from the Arduino's 5V (which is only for testing, not operation), and the external supply itself is verified, this suggests a defect with the PCA9685 board itself in its power input or distribution pathway for the V+ rail.
Could anyone please assist me with this issue?
Thank you for your time and assistance.