Stepper Motors

A stepper motor moves in discrete steps rather than a continuous sweep. Each pulse to the driver advances the motor by one step, so position is tracked by counting steps — no position feedback sensor is needed for open-loop control.

The 28BYJ-48 is the most common starter stepper motor. It runs on 5 V, has an internal gear reduction of ~64:1, and comes bundled with a ULN2003A driver board that accepts 3.3 V logic directly from the ESP32.

// 28BYJ-48 with ULN2003 — Library Manager → "AccelStepper" by Mike McCauley
#include <AccelStepper.h>

// HALF4WIRE (8-step) mode: IN1=23, IN3=21, IN2=22, IN4=19
// Note: AccelStepper expects (pin1, pin2, pin3, pin4) = (IN1, IN3, IN2, IN4)
AccelStepper stepper(AccelStepper::HALF4WIRE, 23, 21, 22, 19);

// 28BYJ-48: 64 electrical steps × gear ratio ≈ 64 = 4096 steps/rev (half-step)
const int STEPS_PER_REV = 4096;

void setup() {
    stepper.setMaxSpeed(1000);       // steps/second
    stepper.setAcceleration(500);    // steps/second²
}

void loop() {
    stepper.moveTo(STEPS_PER_REV);   // one full clockwise revolution
    while (stepper.distanceToGo() != 0) {
        stepper.run();
    }
    delay(500);
    stepper.moveTo(0);               // return to home position
    while (stepper.distanceToGo() != 0) {
        stepper.run();
    }
    delay(500);
}

NEMA 17 is the industry-standard bipolar stepper motor for 3D printers and CNC machines. It delivers significantly more torque than the 28BYJ-48 and supports up to 1/16 microstepping for smooth motion. The A4988 driver requires a separate high-voltage motor supply (8–35 V) and a 3.3 V logic supply.

// NEMA 17 with A4988 driver — STEP / DIR interface
#include <AccelStepper.h>

const int STEP_PIN = 23;
const int DIR_PIN  = 22;
const int EN_PIN   = 21;  // active LOW — pull LOW to enable

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

// NEMA 17 standard: 200 full steps/rev (1.8° per step)
// With 1/16 microstepping on A4988: 3200 steps/rev
const int STEPS_PER_REV = 200;

void setup() {
    pinMode(EN_PIN, OUTPUT);
    digitalWrite(EN_PIN, LOW);       // enable the driver

    stepper.setMaxSpeed(800);
    stepper.setAcceleration(400);
}

void loop() {
    stepper.moveTo(STEPS_PER_REV);
    while (stepper.distanceToGo() != 0) { stepper.run(); }
    delay(500);
    stepper.moveTo(0);
    while (stepper.distanceToGo() != 0) { stepper.run(); }
    delay(500);
}