Lab: DC Motor Control Using an H-Bridge

In this lab I learned to control the functions of a DC motor through a motor driver board that handles power functions for the motor and communicates with an Arduino.

The motor controller on hand was a A4988 Stepper Motor Driver Carrier from Pololu. The A4988 board pinout and basic wiring diagram here:

My setup with the Arduino Mega and a 12-volt DC computer fan looked like this:

While the motor controller was designed for a stepper motor, which has two separate coils, the DC motor I was using only had one so I only need to wire up the “A” motor pins.

Next I added a switch to the circuit that would be read by the Arduino Mega to then set the DC motor to ON or OFF.

Using a tutorial from MarkerGuides.com as a starting point I revised their Arduino sketch into the code below and was able to turn the DC fan motor ON and OFF. I a not entirely sure why but it was necessary toggle the digitalWrite() for the motor driver pin multiple times in the code to set the state to ON or OFF.

/*Example sketch to control a stepper motor with A4988 stepper motor driver and Arduino without a library. More info: https://www.makerguides.com */

// Define stepper motor connections and steps per revolution:
#define dirPin 2
#define stepPin 3
#define switchPin 4
#define stepsPerRevolution 200
int switchState = LOW;

void setup() {
  // configure the serial connection:
  Serial.begin(9600);
  // Declare pins as output:
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(switchPin, INPUT);
}

void loop() {
  
  // if the switch is high, motor will turn on one direction:
    if (digitalRead(switchPin) == HIGH && switchState == LOW) {
      digitalWrite(stepPin, LOW);  // set motor driver high
      digitalWrite(stepPin, HIGH);  // set motor driver high
      digitalWrite(stepPin, LOW);   // set motor driver low
      digitalWrite(stepPin, HIGH);  // set motor driver high
      Serial.println("HIGH");
      switchState = HIGH;
    }
    // if the switch is low, motor will turn in the other direction:
    else if(digitalRead(switchPin) == LOW && switchState == HIGH) {
      digitalWrite(stepPin, LOW);   // set motor driver low
      digitalWrite(stepPin, HIGH);  // set motor driver high
      digitalWrite(stepPin, LOW);  // set motor driver high
      digitalWrite(stepPin, HIGH);  // set motor driver high
      Serial.println("LOW");
      switchState = LOW;
    }

  delay(10);

}