controlling speed and direction of a small DC motor

Introduction

This example shows how to control a small DC motor using the motor shield v3 for Arduino compatible boards.

Scenario

The scenario of use is as shown on this picture:

(c) 2009 Picture courtesy of Rui Costa

Code

The following sketch for Arduino shows how to control the speed and direction of the motor connected as shown in the previous picture.

int dirA = 12;
int dirB = 13;  // not used in this example
int speedA = 10;
int speedB = 11; // not used in this example


void setup()
{
  pinMode (dirA, OUTPUT);
  pinMode (dirB, OUTPUT);
  pinMode (speedA, OUTPUT);
  pinMode (speedB, OUTPUT);
}

void loop()
{
  // move the motor A to one direction increasing speed
  digitalWrite (dirA, HIGH);
  for (int j = 0; j < 255; j += 10) {
     analogWrite (speedA, j);
     delay (100);
  }

delay(1000); // keep the motor rolling for one second

// move the motor A to one direction decreasing speed
  digitalWrite (dirA, HIGH);
  for (int j = 255; j >= 0; j -= 10) {
     analogWrite (speedA, j);
     delay (100);
  }

// stop the motor
  digitalWrite(speedA, LOW);

delay(1000); // keep the motor stopped for one second

}