// connect motor controller pins to Arduino digital pins
// motor two
int enB = 5;
int in3 = 7;
int in4 = 6;
void setup()
{ // set all the motor control pins to outputs
  pinMode(enB, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
}
void demoOne()
{ 
  // this function will run the motor in both directions at a fixed speed
  // turn on motor B
  digitalWrite(in3, HIGH);
  digitalWrite(in4, LOW);
  // set speed to 200 out of possible range 0~255
  analogWrite(enB, 200);
  delay(2000);
  // now change motor directions
  digitalWrite(in3, LOW);
  digitalWrite(in4, HIGH);
  delay(2000);
  // now turn off motors
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW);
}
void demoTwo()
{ // this function will run the motor across the range of possible speeds, 
  // note that maximum speed is determined by the motor itself and the 
  // operating voltage the PWM values sent by analogWrite() are fractions 
  // of the maximum speed possible by your hardware
  // turn on motors
  digitalWrite(in3, LOW);
  digitalWrite(in4, HIGH);
  
// accelerate from zero to maximum speed
for (int i = 0; i < 256; i++) 
  {
    analogWrite(enB, i);
    delay(20);
  }
// decelerate from maximum speed to zero
for (int i = 255; i > 0; --i)
  {
    analogWrite(enB, i);
    delay(20);
  }
  // now turn off motors
  digitalWrite(in3, LOW);
  digitalWrite(in4, LOW); 
}
void loop()
{
  demoOne();
  delay(1000);
  demoTwo();
  delay(1000);
}