int TIP120pin = 11; //Arduino's PMW pin 11
int speedValue;

void setup()  { 
  // nothing happens in setup 
} 

void loop()  { 
  // ramp in from min to max in increments of 5 points:
  for(int speedValue = 0 ; speedValue <= 255; speedValue +=5) { 
    // sets the value (range from 0 to 255):
    analogWrite(TIP120pin, speedValue);         
    // wait for 30 milliseconds to see the effect    
    delay(30);                            
  } 

  // ramp out from max to min in increments of 5 points:
  for(int speedValue = 255 ; speedValue >= 0; speedValue -=5) { 
    // sets the value (range from 0 to 255):
    analogWrite(TIP120pin, speedValue);         
    // wait for 30 milliseconds to see the effect    
    delay(30);                            
  } 
}