Controlling a 28BYJ-48 Stepper Motor with Wemos D1 Mini and ULN2003A

Overview

This guide demonstrates how to control a 28BYJ-48 stepper motor using a Wemos D1 Mini (ESP8266) board and ULN2003A driver module. The 28BYJ-48 is a popular, inexpensive stepper motor commonly used in DIY projects for precise positioning and automation.

Components Required

Wemos D1 Mini (ESP8266 board)
28BYJ-48 stepper motor (5V or 12V version)
ULN2003A stepper motor driver module
Jumper wires
Power supply (5V or 12V depending on motor)
USB cable for programming

Wiring Diagram

flowchart LR
    subgraph "Wemos D1 Mini"
        D1[D1 GPIO5]
        D2[D2 GPIO4]
        D3[D3 GPIO0]
        D4[D4 GPIO2]
    end
    
    subgraph "ULN2003A Driver"
        IN1[IN1]
        IN2[IN2]
        IN3[IN3]
        IN4[IN4]
        VCC[VCC +]
        GND[GND -]
    end
    
    subgraph "28BYJ-48 Motor"
        BLUE[Blue Wire]
        PINK[Pink Wire]
        YELLOW[Yellow Wire]
        ORANGE[Orange Wire]
        RED[Red Wire +5V]
    end
    
    D1 --> IN1
    D2 --> IN2
    D3 --> IN3
    D4 --> IN4
    
    IN1 --> BLUE
    IN2 --> PINK
    IN3 --> YELLOW
    IN4 --> ORANGE
    
    VCC --> RED

Pin Connections

Wemos D1 Mini Pin	ULN2003A Pin	Motor Wire Color
D1 (GPIO5)	IN1	Blue
D2 (GPIO4)	IN2	Pink
D3 (GPIO0)	IN3	Yellow
D4 (GPIO2)	IN4	Orange
5V	VCC (+)	Red
GND	GND (-)	-

Arduino IDE Setup

Install ESP8266 Board Support

Open Arduino IDE and go to File > Preferences. Add this URL to “Additional Boards Manager URLs”:
```
http://arduino.esp8266.com/stable/package_esp8266com_index.json
```
Install ESP8266 Board

Go to Tools > Board > Boards Manager, search for “esp8266”, and install the ESP8266 package.
Select Board

Go to Tools > Board and select “LOLIN(WEMOS) D1 R2 & mini”.
Install Stepper Library

Go to Sketch > Include Library > Manage Libraries, search for “Stepper”, and install the built-in Stepper library.

Basic Control Code

#include <Stepper.h>

// Define number of steps per revolution
const int stepsPerRevolution = 2048;  // 28BYJ-48 has 2048 steps per revolution

// Initialize stepper motor on pins D1, D2, D3, D4
Stepper myStepper(stepsPerRevolution, D1, D3, D2, D4);  // Note the pin order for proper sequence

void setup() {
  // Set the speed to 10 rpm
  myStepper.setSpeed(10);

  // Initialize serial communication
  Serial.begin(115200);
  Serial.println("Stepper Motor Control Ready");
}

void loop() {
  // Rotate clockwise 1 revolution
  Serial.println("Clockwise");
  myStepper.step(stepsPerRevolution);
  delay(1000);

  // Rotate counterclockwise 1 revolution
  Serial.println("Counterclockwise");
  myStepper.step(-stepsPerRevolution);
  delay(1000);
}

Advanced Control Features

Speed Control

// Different speeds for different applications
myStepper.setSpeed(5);   // Slow for precision
myStepper.step(512);     // Quarter turn

myStepper.setSpeed(15);  // Faster for quick movements
myStepper.step(1024);    // Half turn

Microstepping

The 28BYJ-48 can be controlled with half-steps for smoother operation:

// Half-step mode (4096 steps per revolution)
const int halfStepsPerRevolution = 4096;
Stepper myStepper(halfStepsPerRevolution, D1, D3, D2, D4);

Position Control

void rotateDegrees(float degrees) {
  // Calculate steps needed (2048 steps = 360 degrees)
  int steps = (degrees / 360.0) * stepsPerRevolution;
  myStepper.step(steps);
}

// Example usage
rotateDegrees(90);   // Rotate 90 degrees clockwise
rotateDegrees(-45);  // Rotate 45 degrees counterclockwise

WiFi Control (ESP8266 Feature)

Since the Wemos D1 Mini has WiFi capabilities, you can control the motor remotely:

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <Stepper.h>

const char* ssid = "YourWiFiSSID";
const char* password = "YourWiFiPassword";

ESP8266WebServer server(80);
Stepper myStepper(stepsPerRevolution, D1, D3, D2, D4);

void setup() {
  myStepper.setSpeed(10);

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }

  server.on("/clockwise", []() {
    myStepper.step(512);  // Quarter turn
    server.send(200, "text/plain", "Rotated clockwise");
  });

  server.on("/counterclockwise", []() {
    myStepper.step(-512);
    server.send(200, "text/plain", "Rotated counterclockwise");
  });

  server.begin();
}

void loop() {
  server.handleClient();
}

Applications

Robotics and Automation

Robot arm positioning
CNC machine control
Automated blinds/curtains
Camera pan/tilt mechanisms

Measurement Devices

Precision gauges
Antenna rotators
Solar panel trackers
Laboratory equipment

Consumer Products

Vending machines
ATM machines
Printers and scanners
DVD players

Troubleshooting

Motor Not Moving

Check power supply voltage (5V or 12V as required)
Verify all connections are secure
Ensure correct pin mapping in code
Check if ULN2003A module has power

Motor Vibrating but Not Rotating

Wrong stepper motor type (unipolar vs bipolar)
Incorrect coil sequence in code
Insufficient power supply current

Motor Running Slowly

Increase speed setting in setSpeed()
Check power supply capacity
Reduce load on motor shaft

WiFi Connection Issues

Verify SSID and password
Check WiFi signal strength
Ensure ESP8266 firmware is up to date

Performance Specifications

Parameter	Value
Step Angle	5.625° / 64 (half-step mode)
Steps per Revolution	2048 (full step), 4096 (half step)
Rated Voltage	5V or 12V DC
Current per Phase	~150mA
Holding Torque	34.3mN·m (3.3kg·cm)
Operating Temperature	-10°C to +40°C

Safety Considerations

Always disconnect power when making wiring changes
Ensure proper ventilation for motor during extended operation
Use appropriate power supply ratings
Avoid overloading the motor shaft
Keep motor away from flammable materials