int relayPin =  2;    // Relay connected to digital pin 2 
void setup()   {                
  // initialize the digital pin as an output:
  pinMode(relayPin, OUTPUT);     
}
void loop()                     
{
  digitalWrite(relayPin, HIGH);   // set the LED on
  delay(1000);                  // wait for a second
  digitalWrite(relayPin, LOW);    // set the LED off
  delay(1000);                  // wait for a second
}