Experiment 7: Stepper Motor Control via Microcontroller

Objective

To control the rotation and direction of a stepper motor using Arduino and a ULN2003 driver.

Task

Connect stepper motor and driver to Arduino.
Write code to rotate motor clockwise and counter-clockwise.
Vary delay to change motor speed.

⚠️ Important Note:
1. Connect only the Arduino Uno (without any component connections) to the computer via USB.
2. Upload the code to the Arduino.
3. Disconnect the Arduino from the computer and remove the USB cable.
4. Make all component connections using patch cords as per the circuit diagram.
5. Then connect the 9V adapter to provide external power supply to the Arduino.

Circuit Diagram

Board Connections

Connections

Component	Arduino Pin	Description
Stepper Motor IN1	D8	Control input 1
Stepper Motor IN2	D9	Control input 2
Stepper Motor IN3	D10	Control input 3
Stepper Motor IN4	D11	Control input 4
ULN2003 VCC	5V	Power supply for driver
ULN2003 GND	GND	Common ground

Code

// © 2025, Cognifront. Member of The IoT Kits Family.

//Experiment 7: Stepper Motor Control via Microcontroller

// Include the Stepper motor library
#include <Stepper.h>

// Define the number of steps per revolution for the stepper motor
// For a 28BYJ-48 stepper, it's typically 2048 steps per revolution (with gear reduction)
const int stepsPerRevolution = 2048;  

// Create a Stepper object named myStepper
// Connected to digital pins 8, 9, 10, 11 (sequence matters!)
Stepper myStepper(stepsPerRevolution, 8, 10, 9, 11);

void setup() {
  // Start serial communication for debugging and monitoring
  Serial.begin(9600);
  Serial.println("Stepper Motor Speed Test"); // Initial message
}

void loop() {
  // Rotate clockwise (CW) at increasing speeds
  for (int spd = 5; spd <= 10; spd += 5) {
    Serial.print("Rotating CW at ");
    Serial.print(spd);
    Serial.println(" RPM");

    myStepper.setSpeed(spd);                        // Set stepper speed in RPM
    myStepper.step(stepsPerRevolution / 2);         // Rotate 1/2 revolution in CW direction
    delay(500);                                     // Short pause between speed changes
  }

  // Rotate counterclockwise (CCW) at decreasing speeds
  for (int spd = 10; spd >= 5; spd -= 5) {
    Serial.print("Rotating CCW at ");
    Serial.print(spd);
    Serial.println(" RPM");

    myStepper.setSpeed(spd);                        // Set stepper speed in RPM
    myStepper.step(-stepsPerRevolution / 2);        // Rotate 1/2 revolution in CCW direction
    delay(500);                                     // Short pause between speed changes
  }
}

Observation

The stepper motor rotates in both clockwise and counterclockwise directions.
The motor speed changes as per the programmed RPM values.
Smooth operation is observed with correct wiring sequence.

Conclusion

The experiment successfully demonstrates control of a stepper motor’s speed and direction using Arduino and a ULN2003 driver. This forms the basis for applications like robotic motion control, CNC systems, and precise positioning mechanisms.