What I wanted to learn, and why it interested me:  I wanted to learn about the stepper motor because it seemed like a challenge compared to the hobby servo motor we covered before. It interested me because its structure seemed more complex, and the electrical components seemed fun to play with. Moreover, it has a smoother and more delicate movement compared to the hobby servo motor.

Final outcome: I got to my final build through a wiring process that was very challenging for me, along with learning how to code with the stepper motor. Wiring up the stepper motor was quite complex for me, matching all of the respective wires with their regions and learning what all the pins do. I decided on my final creative/exploratory output due to how I saw the stepper motor moves, along with the potentiometer controls.

Process and reflection: 

For this project, I began by focusing on correctly wiring the A4988 stepper motor driver to the Arduino Uno. Before connecting anything to power, I carefully reviewed the driver’s pinout and compared it to both the datasheet and example schematics. I first connected the logic side pins to the Arduino and ensured that RESET and SLEEP were tied together and pulled high so the driver would remain enabled. After that, I connected the motor coils to the output pins, which required identifying the correct wire pairs. Throughout the process, I learned how sensitive the driver is to correct wiring and power management. One of the biggest surprises was how easily the motor would vibrate instead of rotate if even one connection was incorrect. I also gained a stronger understanding of the difference between logic power and motor power, which initially confused me. Overall, I now feel much more confident working with stepper motors and external drivers.  

/*

    60-223 Intro to Physical Computing, fall 2025

    Domain-specific Skill Building exercise: Stepper Motor

    This sketch mainly connects to stepper motor through the A4988

    motor driver. We first read in the inputs through the step and direction

    pins from the A4988 driver, and then the motor knocks from side to

    side. Then, the potentiometer is able to read in input values to

    control the speed of the swinging.

    Pin mapping:

    Arduino pin | role  | details

    ------------------------------

    2             input   step pin

    3             input   direction pin

    A0            output  potentiometer reading

    Released to the public domain by the author, January 2024

    Robert Zacharias, rzachari@andrew.cmu.edu

*/

#include <AccelStepper.h>

const int STEP_PIN = 2;

const int DIR_PIN  = 3;

const int POT_PIN  = A0;

AccelStepper myMotor(AccelStepper::DRIVER, STEP_PIN, DIR_PIN);

// metronome swings

const long SWING_STEPS = 30;

long targetPos = SWING_STEPS;

void setup() {

  Serial.begin(9600);

  // defaults

  myMotor.setAcceleration(800);

  myMotor.setMaxSpeed(600);

  myMotor.setCurrentPosition(0);

  myMotor.moveTo(targetPos);

}

void loop() {

  // read pot

  int potRaw = analogRead(POT_PIN);

  // map pot to speed range

  int speedVal = map(potRaw, 0, 1023, 150, 1200);

  speedVal = constrain(speedVal, 150, 1200);

  myMotor.setMaxSpeed(speedVal);

  // metronome behavior

  if (myMotor.distanceToGo() == 0) {

    targetPos = -targetPos;

    myMotor.moveTo(targetPos);

  }

  myMotor.run();

  // debugging

  static unsigned long lastPrint = 0;

  if (millis() - lastPrint > 250) {

    lastPrint = millis();

    Serial.print("pot=");

    Serial.print(potRaw);

    Serial.print("  maxSpeed=");

    Serial.print(speedVal);

    Serial.print("  pos=");

    Serial.println(myMotor.currentPosition());

  }

}