#define Relay_Pin 2 // Relay pin Number is 2

void setup() {

// put your setup code here, to run   once:

pinMode(Relay_Pin, OUTPUT); 
Serial.begin(9600);

}

void loop() {
 // put your main code here, to run repeatedly: 
digitalWrite(Relay_Pin, HIGH);
Serial.println("Relay ON"); 
delay(2000); 
digitalWrite(Relay_Pin, LOW); 
Serial.println("Relay OFF");
delay(2000);

}