PCA9685 - Multiple Servo Control Using Arduino

Project Overview

This project demonstrates how to control multiple servo motors simultaneously using the PCA9685 16-channel PWM/Servo Driver module with Arduino. The PCA9685 module solves the limitation of Arduino's 6 PWM pins by providing 16 independent PWM outputs through I2C communication.

Original Tutorial: PCA9685 Multiple Servo Control Using Arduino

Features

• Control up to 16 servo motors with a single PCA9685 module
• I2C communication using only 2 Arduino pins (SDA & SCL)
• Cascadable up to 62 modules (992 total outputs)
• Built-in clock eliminates continuous signal transmission
• 3.3V and 5V compatible
• Precise 12-bit PWM resolution

Components Required

Component	Quantity	Description
Arduino Uno R3	1	Main microcontroller
SG90 Servo Motor	8	Standard servo motors
PCA9685 16-Channel Module	1	PWM/Servo driver
External 5V Adapter	1	Power supply for servos
Jumper Wires	As needed	Connections

Pin Configuration

PCA9685 Module Pins

• VCC: Power supply (3.3V to 5V) for module circuitry
• GND: Ground connection
• SDA: I2C data line (connect to Arduino A4)
• SCL: I2C clock line (connect to Arduino A5)
• OE: Output Enable (optional, pull low to disable outputs)
• V+: External power for servos (connect to 5V adapter)

Arduino Connections

Arduino    PCA9685
VCC    ->  5V
GND    ->  GND
A4     ->  SDA
A5     ->  SCL

Circuit Diagram

1. Connect Arduino VCC and GND to PCA9685 VCC and GND
2. Connect Arduino A4 to PCA9685 SDA
3. Connect Arduino A5 to PCA9685 SCL
4. Connect external 5V adapter positive to PCA9685 V+
5. Connect external adapter ground to common ground
6. Connect servos to channels 0-7 on PCA9685

Library Installation

1. Open Arduino IDE
2. Go to Tools > Manage Libraries
3. Search for "Adafruit PWM Servo Driver"
4. Install the library

Code Implementation

Main Code Structure

#include <Adafruit_PWMServoDriver.h>

Adafruit_PWMServoDriver board1 = Adafruit_PWMServoDriver(0x40);

#define SERVOMIN 125  // Minimum pulse length (0 degrees)
#define SERVOMAX 625  // Maximum pulse length (180 degrees)

void setup() {
  Serial.begin(9600);
  Serial.println("16 channel Servo test!");
  board1.begin();
  board1.setPWMFreq(60); // Servos operate at ~60 Hz
}

void loop() {
  // Set all servos to 0 degrees
  for(int i=0; i<8; i++) {
    board1.setPWM(i, 0, angleToPulse(0));
  }
  delay(1000);
  
  // Sweep all servos from 0 to 180 degrees
  for(int angle = 0; angle < 181; angle += 10) {
    for(int i=0; i<8; i++) {
      board1.setPWM(i, 0, angleToPulse(angle));
    }
    delay(100);
  }
}

int angleToPulse(int ang) {
  int pulse = map(ang, 0, 180, SERVOMIN, SERVOMAX);
  Serial.print("Angle: "); Serial.print(ang);
  Serial.print(" pulse: "); Serial.println(pulse);
  return pulse;
}

Key Functions

• setPWM(channel, on, off): Sets PWM values for specific channel
• setPWMFreq(frequency): Sets PWM frequency (60Hz for servos)
• angleToPulse(angle): Converts angle to pulse width

Advanced Features

Multiple PCA9685 Modules

You can cascade multiple PCA9685 modules by:

1. Setting unique I2C addresses using address jumpers (A0-A5)
2. Creating separate objects for each module
3. Default address is 0x40, next would be 0x41, etc.

Adafruit_PWMServoDriver board1 = Adafruit_PWMServoDriver(0x40);
Adafruit_PWMServoDriver board2 = Adafruit_PWMServoDriver(0x41);

I2C Address Configuration

• Board 0: Address = 0x40 (no jumpers)
• Board 1: Address = 0x41 (bridge A0)
• Board 2: Address = 0x42 (bridge A1)
• Board 3: Address = 0x43 (bridge A0 & A1)

Technical Specifications

• PWM Resolution: 12-bit (4096 steps)
• I2C Address: 0x40 (default, configurable)
• Max Current per Pin: 25mA
• Operating Voltage: 3.3V to 5V
• PWM Frequency: Configurable (60Hz for servos)
• Output Resistance: 220Ω series resistor per pin

Troubleshooting

Common Issues

1. Servos not moving: Check external power supply connection
2. Erratic movement: Ensure proper ground connections
3. Communication errors: Verify I2C connections (SDA/SCL)
4. Power issues: Use adequate external power supply (not Arduino 5V)

Important Notes

• Arduino cannot power multiple servos directly
• PCA9685 provides control signals, not power
• All channels share the same PWM frequency
• Maximum 25mA per output pin

Applications

• Robotics: Multi-joint robot arms and legs
• Automation: Multiple actuator control systems
• Animatronics: Character movement systems
• RC Projects: Multi-servo aircraft/vehicle control
• IoT Devices: Smart home automation systems

Working Demonstration

Complete Project Code

The complete Arduino sketch is provided above. Modify the servo count in the for loops if using different numbers of servos.

Project Extensions

1. Web Control: Add ESP32/ESP8266 for web-based servo control
2. Sensor Integration: Add sensors for autonomous servo positioning
3. Multiple Modules: Cascade additional PCA9685 modules for more servos
4. Precise Control: Implement position feedback for closed-loop control

Resources

• Original Circuit Digest Tutorial
• Adafruit PCA9685 Library Documentation
• Servo Motor Basics
• Arduino Projects

License

This project is based on the open-source tutorial from Circuit Digest. Please refer to their terms and conditions for usage rights.

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Created by: Circuit Digest Team
Tutorial Source: https://circuitdigest.com/microcontroller-projects/pca9685-multiple-servo-control-using-arduino