#define ECHO_PIN 2
#define TRIG_PIN 15
int led1 = 19;
int led2 = 18;
int led3 = 5;
int led4 = 21;
int pinBuzzer = 4;

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(pinBuzzer, OUTPUT);
}

float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  return duration * 0.034 / 2 ;
}

void loop() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  float distance = duration * 0.034 / 2 ;

  delay(100);

  if (distance > 50) {
    digitalWrite(led1, HIGH);
    } else {
    digitalWrite(led1, LOW);    
  }
  if (distance > 100) {
    digitalWrite(led2, HIGH);
    } else {
    digitalWrite(led2, LOW);    
  }
  if (distance > 200) {
    digitalWrite(led3, HIGH);
    } else {
    digitalWrite(led3, LOW);    
  }
  if (distance > 300) {
    digitalWrite(pinBuzzer, HIGH);
    delay(distance);
    digitalWrite(pinBuzzer, LOW);
    digitalWrite(led4, HIGH);
    } else {
    digitalWrite(led4, LOW);    
  }
}