#define trigPin 2
#define echoPin 3
#define LEDlampRed 4
#define LEDlampYellow 5
#define LEDlampGreen 6
#define soundbuzzer 7
int sound = 500;

void setup() {
  Serial.begin(9600);  // Perbaikan: 9600 bukan 900
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(LEDlampRed, OUTPUT);
  pinMode(LEDlampYellow, OUTPUT);
  pinMode(LEDlampGreen, OUTPUT);
  pinMode(soundbuzzer, OUTPUT);
}

void loop() {
  long durationindigit, distanceincm;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  durationindigit = pulseIn(echoPin, HIGH);  // Perbaikan: pulseIn bukan pulseln
  distanceincm = (durationindigit / 5) / 29.1;

if (distanceincm < 50) {
  digitalWrite(LEDlampGreen, HIGH);
} else {
  digitalWrite(LEDlampGreen, LOW);
}

if (distanceincm < 20) {
  digitalWrite(LEDlampYellow, HIGH);
} else {
  digitalWrite(LEDlampYellow, LOW);
}

if (distanceincm < 5) {
  digitalWrite(LEDlampRed, HIGH);
  sound = 1000;
} else {
  digitalWrite(LEDlampRed, LOW);
}

if (distanceincm > 5 || distanceincm <= 0) {
  Serial.println("output the permissible range of distances");
  noTone(soundbuzzer);  // Perbaikan: nonTone bukan noTone
} else {
  Serial.print(distanceincm);
  Serial.println(" cm");
  tone(soundbuzzer, sound);
}

delay(300);
}