int relayPin1 = 4;
int relayPin2= 2 ;

void setup()
{
  pinMode(relayPin1,OUTPUT);
  pinMode(relayPin2,OUTPUT);
}

void loop()
{
  digitalWrite(relayPin1, HIGH);
  digitalWrite(relayPin2, LOW);
  delay(500);
  digitalWrite(relayPin1, LOW);
  digitalWrite(relayPin2, HIGH);
  delay(500);

}