int relay_1 = 7;
/*int relay_2 = 7;
int relay_3 = 8;
int relay_4 = 12;*/

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  pinMode(relay_1, OUTPUT);
  /*pinMode(relay_2, OUTPUT);
  pinMode(relay_3, OUTPUT);
  pinMode(relay_4, OUTPUT);*/

}

void loop() {

  digitalWrite(relay_1, HIGH);
  /*digitalWrite(relay_2, HIGH);
  digitalWrite(relay_3, HIGH);
  digitalWrite(relay_4, HIGH);*/

  Serial.println("All relays ON");

  delay(1000);

  digitalWrite(relay_1, LOW);
  /*digitalWrite(relay_2, LOW);
  digitalWrite(relay_3, LOW);
  digitalWrite(relay_4, LOW);*/

  Serial.println("All relays OFF");

  delay(1000);
}