Arduino Stepper Motor Control with A4988 Driver and NEMA 17 Motor

Learning how to control a stepper motor using a microcontroller like Arduino can be incredibly useful for various projects. In this tutorial, we’ll use an Arduino UNO to control a NEMA 17 stepper motor via an A4988 stepper motor driver. This guide walks you through wiring, power setup, and programming without using libraries to control the motor in both clockwise and counterclockwise directions.

Interfacing Arduino, A4988, and NEMA 17

To start, the wiring diagram used in this tutorial is shown below:

Connecting NEMA 17 to the A4988 Stepper Motor Driver

The NEMA 17 is a bipolar stepper motor with four wires. Two wires belong to each of the motor’s internal coils.

Use a multimeter’s continuity tester to identify which two wires belong to the same coil. If there’s continuity, those wires belong to the same coil.
Connect one coil’s wires to the 2A and 2B pins on the A4988 driver.
Connect the other coil’s wires to the 1A and 1B pins.

Powering the A4988 Driver

Connect the VMOT pin to the positive terminal of a 12V power supply.
Connect the negative terminal to the GND pin just below the VMOT pin.
Add a 100µF capacitor between VMOT and GND to smooth the power signal. This is critical for proper operation of the A4988 and motor.

If the power supply voltage is insufficient, the stepper motor will not spin.

Connecting Arduino to the A4988 Driver

Pin Functions:

!Enable Pin: Enables/disables the A4988 driver. It’s active low, meaning the driver is enabled when this pin is LOW. You can leave it unconnected since it has an internal pull-down resistor.
MS1, MS2, MS3: Used for micro-stepping resolution selection. For full-step mode, leave these pins unconnected; internal pull-down resistors will keep them at logic LOW.
!SLEEP and !RESET Pins: Controls sleep and reset functions. Tie these pins together for continuous operation.
STEP Pin: Receives pulses from the Arduino to control the speed of the stepper motor. The speed depends on the pulse duration.
DIR Pin: Controls the motor’s rotation direction.
- HIGH: Clockwise rotation
- LOW: Counterclockwise rotation

Wiring:

Connect the STEP pin to Arduino digital pin 9.
Connect the DIR pin to Arduino digital pin 8.
Connect the VDD pin to the Arduino’s 5V.
Connect the A4988 GND to the Arduino GND.

Realizing the Circuit on a Breadboard

The complete circuit, including Arduino, A4988, and NEMA 17, can be assembled on a breadboard. Here’s how it looks:

Programming Arduino for Stepper Motor Control

In this example, we’ll rotate the NEMA 17 motor one full cycle clockwise, pause, and then rotate it one full cycle counterclockwise. The NEMA 17 has a 1.8° step angle, meaning it requires 200 pulses (360° / 1.8°) for a full rotation.

Arduino Code (Without Libraries)

// defines pins numbers
const int stepPin = 9;
const int dirPin = 8;

void setup() {
// Sets the STEP and DIR pins as Outputs
pinMode(stepPin,OUTPUT);
pinMode(dirPin,OUTPUT);
}

void loop() {
digitalWrite(dirPin,HIGH); // Send HIGH pulse to rotate the motor in clockwise direction
//For one full cycle rotation, send 200 pulses
for(int i = 0; i < 200; i++) {
digitalWrite(stepPin,HIGH);
delayMicroseconds(500);	//500us delay
digitalWrite(stepPin,LOW);
delayMicroseconds(500);	//500us delay
}
delay(1500); // wait for 1.5sec
digitalWrite(dirPin,LOW); // Send LOW pulse to rotate the motor in anti-clockwise direction
// Send 200 pulses to rotate the motor one full cycle in anti-clockwise direction
for(int i = 0; i < 200; i++) {
digitalWrite(stepPin,HIGH);
delayMicroseconds(500); //500us delay
digitalWrite(stepPin,LOW);
delayMicroseconds(500); //500us delay
}
delay(1500);   // wait for 1.5sec
}

Explanation

Speed Control: The duration of the pulse on the STEP pin determines motor speed. Shorter pulses increase speed; longer pulses decrease it.
Direction Control: The DIR pin sets the direction. HIGH for clockwise, LOW for counterclockwise.

Video Demonstration

Watch this video to see the NEMA 17 stepper motor in action: