Materials Used

Wiring Instructions

Rotary Encoder Connections:
• CLK → Pin 3
• DT → Pin 2
• SW (button) → Pin 1
• + → 5V
• GND → GND

Servo Motor Connections:
• Signal (Orange/Yellow) → Pin 7
• Power (Red) → 5V
• Ground (Brown/Black) → GND

L293D Motor Driver Connections:
• ENABLE → Pin 52 (PWM)
• INPUT 1 (DIRA) → Pin 50
• INPUT 2 (DIRB) → Pin 46
• OUTPUT 1 & 2 → DC Fan Motor
• VCC1 → 5V (logic power)
• VCC2 → External Power Supply (motor power)
• GND → GND (both logic and motor grounds)

Circuit Diagram

Project Photos & Demo

Arduino Code

#include <Servo.h>

Servo servo;

// ===== Rotary Encoder Pins =====
const int clkPin = 3;
const int dtPin  = 2;
const int swPin  = 1;

// ===== Servo =====
const int servoPin = 7;
int angle = 90;
const int stepSize = 10;
int lastClk;

// ===== L293D Motor Driver =====
const int ENABLE = 52;
const int DIRA   = 50;
const int DIRB   = 46;

// ===== Fan Control =====
int mode = 0;  // 0 = OFF, 1 = MEDIUM, 2 = FAST

// ===== PWM Levels =====
const int KICK_POWER = 255;
const int MEDIUM_POWER = 170;
const int FAST_POWER = 255;

void setup() {
  // Servo
  servo.attach(servoPin);
  servo.write(angle);

  // Encoder
  pinMode(clkPin, INPUT);
  pinMode(dtPin, INPUT);
  pinMode(swPin, INPUT_PULLUP);
  lastClk = digitalRead(clkPin);

  // Motor driver
  pinMode(ENABLE, OUTPUT);
  pinMode(DIRA, OUTPUT);
  pinMode(DIRB, OUTPUT);

  // Fixed direction
  digitalWrite(DIRA, HIGH);
  digitalWrite(DIRB, LOW);

  analogWrite(ENABLE, 0);  // fan off
}

void loop() {

  handleEncoder();
  handleFanButton();

}

// ===== ROTARY ENCODER → SERVO =====
void handleEncoder() {
  int currentClk = digitalRead(clkPin);

  if (currentClk != lastClk && currentClk == HIGH) {
    if (digitalRead(dtPin) == currentClk) {
      angle += stepSize;
    } else {
      angle -= stepSize;
    }

    angle = constrain(angle, 0, 180);
    servo.write(angle);
  }

  lastClk = currentClk;
}

// ===== BUTTON → FAN MODE =====
void handleFanButton() {
  if (digitalRead(swPin) == LOW) {
    delay(150);  // debounce

    mode++;
    if (mode > 2) mode = 0;

    switch (mode) {

      case 0:
        // OFF
        analogWrite(ENABLE, 0);
        break;

      case 1:
        // MEDIUM with aggressive jumpstart
        analogWrite(ENABLE, KICK_POWER);
        delay(1000);              // longer kick
        analogWrite(ENABLE, 0);
        delay(50);                // brief drop
        analogWrite(ENABLE, KICK_POWER);
        delay(500);
        analogWrite(ENABLE, MEDIUM_POWER);
        break;

      case 2:
        // FAST (full power)
        analogWrite(ENABLE, FAST_POWER);
        break;
    }

    // wait for button release
    while (digitalRead(swPin) == LOW);
    delay(150);
  }
}

🔧 Troubleshooting

Having issues with your circuit? Check these common problems and solutions:

What You Learned