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ESP32-S3 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 ESP32-S3 DevKitC-1 and turning live in your browser: a quarter turn forward, a quarter turn back, with the shaft angle drawn as it goes.

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  • 3.3 V logic
  • Library: Stepper.h
  • IN1 to IN4 on 4, 5, 6, 7
  • 2048 steps a turn
ESP32-S3 · 28BYJ-48 Stepperlive0.000 s 0.00x
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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.
Connections

Wiring the 28BYJ-48 Stepper to the ESP32-S3

Four control wires to 4, 5, 6, 7, and the motor’s power from 5V. It uses the stock Stepper library.

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

28BYJ-48 Stepper pinESP32-S3 pinWhy
IN1GPIO 4Coil A, through the ULN2003’s first Darlington.
IN2GPIO 5Coil B.
IN3GPIO 6Coil C.
IN4GPIO 7Coil D.
VCC (+)5VThe motor’s 5 V supply: a couple of hundred milliamps, more than USB likes to spare.
GND (-)GCommon ground.

Power

The motor runs from 5V, while IN1 to IN4 come from 3.3 V pins. The ULN2003 switches happily from 3.3 V, so no level shifting is needed. On a real bench, a stepper on USB power can brown out the board when it starts; a separate 5 V supply with the grounds joined is safer.

Pins to leave alone on the ESP32-S3

GPIO 19 and 20 are the USB port’s data lines, GPIO 35 to 37 belong to the PSRAM on octal-PSRAM boards such as the N8R8, and GPIO 0, 3, 45 and 46 are strapping pins.

On a real bench

The DevKitC-1 has two USB sockets: UART for uploading and the serial monitor, USB for the S3’s own USB device. Plug into UART while you work with the 28BYJ-48 Stepper. The board is wide, so a single breadboard leaves only one row free on one side.

The sketch

The code, and what it does.

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 ESP32-S3
#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, 4, 6, 5, 7);

void setup() {
  Serial.begin(115200);
  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(115200) opens the serial monitor. Serial is UART0 on the board’s UART socket, at 115200 baud in this sketch.

Pitfalls

Common mistakes with the 28BYJ-48 Stepper on the ESP32-S3

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.

FAQ

Questions and answers

Can I simulate a 28BYJ-48 stepper with an ESP32-S3 DevKitC-1?

Yes. The circuit at the top of this page is an ESP32-S3 DevKitC-1 with a 28BYJ-48 stepper and ULN2003 driver, running in your browser on a simulated ESP32-S3 (Xtensa LX7). 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.

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