Dual Stepper Differential Bevel Gear Mechanism

This project is a compact, fully 3D-printable dual-stepper differential gear system designed to be controlled by a microcontroller.

The mechanism uses two 28BYJ-48 stepper motor units mounted on a shared axis, driving a central bevel gear assembly. By controlling the motors independently, you can precisely manipulate the output motion.

🎮 Microcontroller Control (ESP32 Example)

This system is designed to be paired with a microcontroller such as an ESP32 DevKit V1, using a joystick or other input device.

With simple control logic:

• Push joystick forward → both motors move together
• Push left/right → motors rotate in opposite directions
• Diagonal movement → blended motion

This creates a smooth and intuitive control system ideal for interactive projects.

⚙️ How It Works

The mechanism acts as a mechanical mixer:

• 🔁 Same motor direction → rotational output
• 🔄 Opposite directions → differential motion
• 🎯 Balanced input → stable center (no movement)

This makes it useful for applications where controlled rotation without translation is required.

🧱 Design Features

• Fully 3D-printable
• Compact and modular layout
• Smooth bevel gear interaction
• Designed for common hobby electronics
• Easy integration with microcontrollers (ESP32 / Arduino)

🚀 Use Cases

• Turret or pan control systems
• Robotics joints
• Camera mounts
• Interactive displays

• STEM / engineering demonstrations
   

  Code can easily be customized in your favourite AI model.  

🔌 ESP32 Pin Mapping (D# style)

🕹️ Joystick

⚙️ Stepper Motor A (Left)

⚙️ Stepper Motor B (Right)

🔋 Power

⚠️ Important Notes 

GPIO 34 & 35 are input-only → perfect for joystick

Do NOT power motors from ESP32 5V pin

Use external 5V for stepper drivers

Common ground is required

🧠 Quick Summary (for users)

D34 / D35 → joystick

D14–27 → motor A

D33–19 → motor B

Here is the sample code to copy and paste in Arduino IDE app:

#include <AccelStepper.h>

// ---- Motor pins ----
#define M1_IN1 14
#define M1_IN2 27
#define M1_IN3 26
#define M1_IN4 25

#define M2_IN1 33
#define M2_IN2 32
#define M2_IN3 18
#define M2_IN4 19

// ---- Joystick ----
#define JOY_X 34
#define JOY_Y 35

AccelStepper stepperA(AccelStepper::HALF4WIRE, M1_IN1, M1_IN3, M1_IN2, M1_IN4);
AccelStepper stepperB(AccelStepper::HALF4WIRE, M2_IN1, M2_IN3, M2_IN2, M2_IN4);

// ---- tuning ----
float maxSpeed = 800;
float smoothing = 0.15;

// deadzones tuned for ESP32 stability
float inputDeadzone = 0.20;
float zeroLock = 0.18;

// smoothing state
float smoothX = 0;
float smoothY = 0;

// ---------------- FILTERED ADC READ ----------------
float readFiltered(int pin) {
 long sum = 0;
 for (int i = 0; i < 5; i++) {
   sum += analogRead(pin);
 }
 return sum / 5.0;
}

// ---------------- NORMALIZED AXIS ----------------
float readAxis(int pin) {
 float val = readFiltered(pin);

 // center around ~2048
 val = (val - 2048.0) / 2048.0;

 // input deadzone
 if (abs(val) < inputDeadzone) return 0;

 return val;
}

void setup() {
 analogReadResolution(12);

 stepperA.setMaxSpeed(maxSpeed);
 stepperB.setMaxSpeed(maxSpeed);
}

void loop() {

 // ---- read joystick ----
 float x = readAxis(JOY_X);
 float y = readAxis(JOY_Y);

 // ---- smoothing ----
 smoothX += smoothing * (x - smoothX);
 smoothY += smoothing * (y - smoothY);

 // ---- mix ----
 float motorA = smoothY + smoothX;
 float motorB = smoothY - smoothX;

 // ---- TRUE ZERO LOCK (prevents drift) ----
 if (abs(smoothX) < zeroLock && abs(smoothY) < zeroLock) {
   motorA = 0;
   motorB = 0;
 }

 // ---- normalize ----
 float maxVal = max(abs(motorA), abs(motorB));
 if (maxVal > 1.0) {
   motorA /= maxVal;
   motorB /= maxVal;
 }

 // ---- drive ----
 stepperA.setSpeed(motorA * maxSpeed);
 stepperB.setSpeed(motorB * maxSpeed);

 stepperA.runSpeed();
 stepperB.runSpeed();
}