A simple watering system using a relay to activate a peristaltic pump

arduino-watering-relay.ino

const int RELAY_PIN = 2;
unsigned long LONG_DELAY_MS = 43200000; // 12 hours expressed in milliseconds
unsigned int WATERING_TIME = 2000;
unsigned long startMillis;

void setup() {
  pinMode(RELAY_PIN, OUTPUT);
  startMillis = millis();
  Serial.begin(9600);
  digitalWrite(RELAY_PIN, LOW);
  Serial.print("Long delay: ");
  Serial.println(LONG_DELAY_MS);
}

void loop() {
  
  if (millis() - startMillis > LONG_DELAY_MS){
    digitalWrite(RELAY_PIN, HIGH);
    Serial.println(millis());
    Serial.println("---------");
    Serial.println("watering!");
    Serial.println("---------");
    // reset the timer
    startMillis = millis();
    // wait the required time
    delay(WATERING_TIME);
  }
  else {
    digitalWrite(RELAY_PIN, LOW);
  }
}