A4988 Stepper Driver with Heatsink

Pick a microstep mode

Three pins decide how finely the driver divides each step. Choose a mode to see the steps per turn for a standard 1.8° NEMA 17 motor.

Specifications

Pinout

What you can build

If it moves in exact steps, the A4988 can drive it.

Wiring it to Arduino UNO

Important: always connect the motor before switching on the power, and never unplug the motor while the board is powered. Doing so can destroy the driver. Also join the grounds of the Arduino and the motor supply.

Basic Arduino code

This sketch turns the motor one full revolution one way, waits, then turns it back. It assumes a 1.8° motor (200 steps per turn) with the MS pins left unconnected.

const int stepPin = 3;
const int dirPin = 2;
const int enPin = 8;
void setup() {
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enPin, OUTPUT);
  digitalWrite(enPin, LOW);   // LOW = driver on
}
void loop() {
  digitalWrite(dirPin, HIGH); // one direction
  for (int i = 0; i < 200; i++) {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(1000);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(1000);
  }
  delay(1000);
  digitalWrite(dirPin, LOW);  // other direction
  for (int i = 0; i < 200; i++) {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(1000);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(1000);
  }
  delay(1000);
}

To spin faster, reduce the 1000 microsecond delays. To use 1/16 microstepping, connect MS1, MS2 and MS3 to 5V and change 200 to 3200 steps per turn.

Set the motor current first

Turn the small trimmer on the board to set the current limit. Check the marking on the small current-sense resistors (for example R050, R068 or R100) and use: Vref = current × 8 × resistor value. For a 0.1 Ω resistor, a 1A limit means about 0.8V. Measure Vref between the trimmer’s metal top and GND with a multimeter. Set the current at or just below your motor’s rated current, and always use the heatsink.

Questions buyers ask