Minimum Viable Product: Pan-Tilt Turret System

Minimum Viable Product

This week focused on tackling the most challenging aspects of my final project by developing both the hardware and software components independently. I completed the mechanical pan-tilt servo mechanism and integrated it with electronic control, while also building upon Week 6's ESP32-CAM human detection system. These parallel development tracks represent the core subsystems that will combine into the final AI-controlled turret.

CAD Model

The pan-tilt platform was designed in Fusion 360 with careful consideration for servo mounting, gear ratios, and structural rigidity. The design incorporates a lazy susan bearing for the pan axis and a direct-drive servo for the tilt axis, providing smooth motion across the full range of movement.

Gear train and servo mounting detail

Circuit Design

The control system uses an ESP32 microcontroller to read two potentiometers and control two MG996R servos. The servos are powered by a separate 5V AC-to-DC power supply to handle their current requirements, while the potentiometers run on the ESP32's 3.3V rail.

Circuit schematic showing connections and power distribution

Physical breadboard implementation with components

Code Implementation

The code uses C++ classes to encapsulate potentiometer reading and servo control functionality. The ServoWrapper and Potentiometer classes provide clean interfaces for hardware interaction, making the code modular and easy to extend. The loop continuously reads potentiometer values and maps them to servo positions without using delay().

#include <ESP32Servo.h>

class Potentiometer {
  int potPin;

  public:
    Potentiometer(int pin) {
      potPin = pin;
      pinMode(potPin, INPUT);
    }

    int read() {
      return analogRead(potPin);
    }
};

// Wrapper function to add more functionality later
class ServoWrapper {
  Servo servo;
  int servoPin;
  int startPos;

  public:
    ServoWrapper(int pin, int pos) {
      servoPin = pin;
      startPos = pos;
    }

    void attach() {
      servo.attach(servoPin);
      servo.write(startPos);
    }

    void move(int pos) {
      servo.write(pos);
    }
};

ServoWrapper s1(32, 0);
ServoWrapper s2(33, 0);
Potentiometer p1(34);
Potentiometer p2(35);

void setup() {
  Serial.begin(115200);
  delay(200);                         // let USB/driver settle
  Serial.println("\nBooting…");
  s1.attach();
  s2.attach();
}

void loop() {
  // put your main code here, to run repeatedly:
  int potVal1 = p1.read();
  int potVal2 = p2.read();

  Serial.printf("Pot 1: %d  Pot 2: %d\n", potVal1, potVal2);

  int servoVal1 = map(potVal1, 0, 4095, 0, 180);
  int servoVal2 = map(potVal2, 0, 4095, 0, 180);

  s1.move(servoVal1);
  s2.move(servoVal2);
}

Signal Characteristics

Using an oscilloscope, I measured the PWM signals sent from the ESP32 (pins 32 and 33) to the MG996R servos. The analysis revealed the timing characteristics of standard RC servo control signals and how pulse width modulation translates to servo position.

Minimum pulse: 520µs (0° position)

Signal period: 20ms between pulses (50Hz)

Maximum pulse: 2.44ms (180° position)