Open the editorEditor
Arduino Uno · 28BYJ-48 Stepper

Arduino Uno 28BYJ-48 Stepper Simulator: Wiring, Code and a Live Circuit

This is a 28BYJ-48 stepper motor on its ULN2003 driver board, wired to an Arduino Uno and turning live in your browser: a quarter turn forward, a quarter turn back, with the shaft angle drawn as it goes.

Four control wires to 8, 9, 10, 11, and the motor’s power from 5V. It uses the stock Stepper library.

Run it in the editorRead the code
  • 5 V logic
  • Library: Stepper.h
  • IN1 to IN4 on 8, 9, 10, 11
  • 2048 steps a turn
Arduino Uno · 28BYJ-48 Stepperlive0.000 s 0.00x
Click to open it in the editor
The circuit itself, running on the simulator with the sketch below. Press what can be pressed; click anything else to open it in the editor.

Wiring the 28BYJ-48 Stepper to the Arduino Uno

Every connection in the circuit above, with the board’s own pin names.

28BYJ-48 Stepper pinArduino Uno pinWhy
IN1pin 8Coil A, through the ULN2003’s first Darlington.
IN2pin 9Coil B.
IN3pin 10Coil C.
IN4pin 11Coil D.
VCC (+)5VThe motor’s 5 V supply: a couple of hundred milliamps, more than USB likes to spare.
GND (-)GNDCommon ground.

The ULN2003 board carries the coil current, so the Arduino Uno’s pins only drive its inputs. The motor’s 5 V comes from the 5V pin here; on a real bench a separate 5 V supply with the grounds joined keeps the board from resetting.

Pins to leave alone on the Arduino Uno

Pins 0 and 1 are the USB serial port on a real Uno, so anything wired there fights the upload and the serial monitor. Pin 13 carries the onboard LED.

On a real bench

On a real bench the Uno stands beside the breadboard: the 28BYJ-48 Stepper goes into the breadboard and male-to-male jumpers run from the Uno’s female headers to its rows. Power the Uno from USB while you build, and unplug it before you move a wire.

The code

The sketch the circuit above runs. Open it in the editor, change a line and press Run: it compiles in your browser.

28BYJ-48 stepper on Arduino Uno
#include <Stepper.h>

// The 28BYJ-48 through its ULN2003 board: 2048 full steps a turn.
const int STEPS_PER_TURN = 2048;

// Note the order: IN1, IN3, IN2, IN4. The Stepper library's sequence
// matches the motor's coils that way.
Stepper motor(STEPS_PER_TURN, 8, 10, 9, 11);

void setup() {
  Serial.begin(9600);
  motor.setSpeed(12);               // rpm; the 28BYJ-48 tops out near 15
  Serial.println("Stepper ready");
}

void loop() {
  Serial.println("Quarter turn forward");
  motor.step(STEPS_PER_TURN / 4);
  delay(300);
  Serial.println("Quarter turn back");
  motor.step(-STEPS_PER_TURN / 4);
  delay(300);
}

Stepper motor(2048, IN1, IN3, IN2, IN4) is the line everybody gets wrong. The library energizes its four pins in a fixed sequence, and for this motor the middle two have to be swapped, or it buzzes in place instead of turning.

setSpeed(12) sets the step rate for 12 revolutions a minute. step(512) blocks until a quarter turn is done, about 1.25 seconds at that speed, then step(-512) comes back. Nothing else in the sketch runs while it steps; AccelStepper.h is the library for moving without blocking.

Serial.begin(9600) opens the serial monitor. Serial goes over the USB cable, and the serial monitor in the editor reads it at whatever baud rate the sketch sets.

Common mistakes with the 28BYJ-48 Stepper on the Arduino Uno

The pin order in the constructor

Stepper(steps, IN1, IN2, IN3, IN4) makes the 28BYJ-48 vibrate without turning. The order has to be IN1, IN3, IN2, IN4, as in the sketch.

Asking for more than 15 rpm

The gearbox makes this motor slow. Above about 15 rpm it skips steps or stalls, and because nothing reports the shaft’s position, the sketch never knows. Keep setSpeed() low.

Assuming the motor knows where it is

A stepper has no sensor: the sketch counts the steps it sent. After a stall or a power cycle that count is wrong, which is why real machines home against a limit switch at start-up.

Questions and answers

Can I simulate a 28BYJ-48 stepper with an Arduino Uno?

Yes. The circuit at the top of this page is an Arduino Uno with a 28BYJ-48 stepper and ULN2003 driver, running in your browser on a simulated ATmega328P. The simulated motor follows the coil sequence on the four pins, so a wrong order makes it stall on the drawing too. Press Run it in the editor to change the wiring or the code; it is free and needs no account.

How many steps is one turn?

2048 in full-step mode and 4096 in half-step mode, because of the motor’s 64 to 1 gearbox. The Stepper library uses full steps.

Can I run two steppers at once?

Not with Stepper.h, whose step() blocks. AccelStepper.h moves several motors at once by calling run() for each in loop().

What about a NEMA 17?

A NEMA 17 needs a current-limiting driver such as the A4988, driven with STEP and DIR pins. The simulator has both, and the A4988 tutorial covers it.

Build your own 28BYJ-48 Stepper project

Open this circuit in the editor, change the wiring or the code, and keep your version in a free account.

Start building freeOpen the editor