int placa1 = 11;
int cont = 0;
int i = 1;

void setup()
{
  // begin the serial communication
  Serial.begin(9600);
  pinMode(placa1, OUTPUT);
  analogWrite(placa1, 0);
}

void loop()
{
  byte val;

  

 for(i = 0; i <= 255; i++)
  {
   analogWrite(placa1, i);
   delay(5);
  }
  
 for(i = 254; i >= 0; i--)
  {
   analogWrite(placa1, i);
   delay(10);
  }
  
  delay(200);

}