const int TRIG = 9;
const int ECHO = 10;
const int BUZZER = 8;
const int LED = 7;

const int SEUIL_BAS = 15; // cm (ajuster selon ton réservoir)

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(BUZZER, OUTPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

long mesurerDistance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  long duree = pulseIn(ECHO, HIGH);
  return duree * 0.034 / 2;
}

void loop() {
  long distance = mesurerDistance();
  Serial.print("Distance : ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance > SEUIL_BAS) {
    digitalWrite(LED, HIGH);
    digitalWrite(BUZZER, HIGH);
    delay(200);
    digitalWrite(BUZZER, LOW);
    delay(800);
  } else {
    digitalWrite(LED, LOW);
    digitalWrite(BUZZER, LOW);
    delay(1000);
  }
}