⚙️ DC Motor Speed Control (Arduino + L293N)

🎯 Objectives

Design and implement a microcontroller-based system that operates a DC motor with varying and constant speeds based on defined timing patterns, simulating industrial processes where precise speed control is critical.

🧩 Problem Description

🛠️ System Description

• Microcontroller: Arduino Uno (ATmega328P) — 8-bit MCU with 6 PWM channels.
• Motor Driver: L293N H-bridge — bidirectional control with PWM speed control.
• Motor: 12V brushed DC motor, continuous rotation, PWM capable.
• Power: 12V DC for motor, 5V regulated for Arduino.
• Software: Arduino IDE (development) and Proteus (simulation).

💻 Arduino Source Code

// Arduino Code for DC Motor Control

const int ENA = 9;    // PWM pin for speed control
const int IN1 = 13;   // Direction control
const int IN2 = 12;   // Direction control

// Speed parameters (PWM values 0-255)
const int speed1 = 50;   // Minimum speed to overcome friction
const int speed2 = 255;  // Maximum speed

void setup() {
  pinMode(ENA, OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);

  // Initial direction (forward)
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);

  Serial.begin(9600);
}

void loop() {
  Serial.println("Pattern 1:");
  Pattern1();

  delay(5000); // Pause between patterns

  Serial.println("Pattern 2:");
  Pattern2();

  delay(5000); // Pause before repeating
}

void printSpeed(int speed) {
  analogWrite(ENA, speed);
  Serial.print("Speed set to: ");
  Serial.print(speed);
  Serial.print(" (");
  Serial.print(map(speed, 0, 255, 0, 100));
  Serial.println("%)");
}

// Pattern 1: Constant acceleration and deceleration
void Pattern1() {
  const unsigned long rtime = 90000; // 1.5 minutes in ms
  const int steps = 100;

  // Ramp up
  for (int i = 0; i <= steps; i++) {
    int speed = map(i, 0, steps, speed1, speed2);
    printSpeed(speed);
    delay(rtime / steps);
  }

  // Ramp down
  for (int i = steps; i >= 0; i--) {
    int speed = map(i, 0, steps, speed1, speed2);
    printSpeed(speed);
    delay(rtime / steps);
  }

  // Turn off
  printSpeed(0);
  Serial.println("Motor OFF");
}

// Pattern 2: Double speed every 30s
void Pattern2() {
  const unsigned long sTime = 30000; // 30 seconds
  int baseSpeed = 60; // ~25% of max
  int speedLevels[] = { baseSpeed, baseSpeed*2, baseSpeed*4, baseSpeed*2, baseSpeed, 0 };

  for (int i = 0; i < 6; i++) {
    printSpeed(speedLevels[i]);
    Serial.print("Step "); Serial.print(i + 1);
    Serial.print(" - Speed: "); Serial.println(speedLevels[i]);
    delay(sTime);
  }

  Serial.println("Motor OFF");
}

📈 Simulation Results

• Pattern 1: Smooth acceleration to peak over 90s and symmetric deceleration to zero.
• Pattern 2: Step-wise speed doubling every 30s, then mirrored down to OFF.

🌍 Importance & Use Cases

This controller demonstrates techniques used in conveyors, pumps, fans, and process lines, where precise speed profiles reduce mechanical stress, improve throughput, and enable repeatable automation cycles.

🔗 Repository

View on GitHub