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Why a Motor Driver?

Arduino GPIO pins can only source/sink ~40 mA — not enough to drive a motor directly. Motor drivers (H-bridges) use transistors to switch higher currents from an external power supply while keeping the Arduino safely isolated.

DC Motor with L298N

The L298N drives two DC motors. For one motor:

Arduino pin 6 (PWM) → L298N ENA   (speed)
Arduino pin 7       → L298N IN1   (direction)
Arduino pin 8       → L298N IN2   (direction)
External 6–12V      → L298N VIN
GND shared between Arduino and L298N

const int ENA = 6, IN1 = 7, IN2 = 8;

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

void forward(int speed) {
  analogWrite(ENA, speed); // 0–255
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
}

void backward(int speed) {
  analogWrite(ENA, speed);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
}

void stopMotor() { analogWrite(ENA, 0); }

Servo Control

Servos receive a PWM signal (50 Hz, 1–2 ms pulse width) to hold a specific angle. Arduino’s Servo library handles the timing:

#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(9); // any digital pin
}

void loop() {
  for (int angle = 0; angle <= 180; angle += 5) {
    myServo.write(angle);
    delay(20);
  }
  for (int angle = 180; angle >= 0; angle -= 5) {
    myServo.write(angle);
    delay(20);
  }
}

Stepper Motor (28BYJ-48 + ULN2003)

The 28BYJ-48 is an inexpensive 5V geared stepper (2048 steps/rev) driven by a ULN2003 board.

#include <AccelStepper.h> // install: "AccelStepper" by Mike McCauley

// ULN2003 driver pins: IN1 IN2 IN3 IN4
AccelStepper stepper(AccelStepper::HALF4WIRE, 8, 10, 9, 11);

void setup() {
  stepper.setMaxSpeed(500);    // steps/sec
  stepper.setAcceleration(200);
  stepper.moveTo(2048);        // one full revolution
}

void loop() {
  if (stepper.distanceToGo() == 0) {
    stepper.moveTo(-stepper.currentPosition()); // reverse
  }
  stepper.run(); // call as often as possible — non-blocking
}

Exercises

1. Control DC motor speed with a potentiometer; reverse direction with a button
2. Use a servo as a “gauge needle” that maps to ADC reading (0 → 0°, 1023 → 180°)
3. Combine stepper + button: press to advance exactly 512 steps (quarter turn)