#include <LiquidCrystal_I2C.h>
#include <Wire.h>

LiquidCrystal_I2C lcd (0x27, 16, 2);

#define trig 12
#define echo 11
#define red 2
#define yellow 3
#define green 4
#define buzz 5

long duration;
int distance;
int frequency;

void setup() {
  
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(buzz, OUTPUT);
  lcd.setCursor (1, 0);
  lcd.print ("Distance:");

}

void loop() {
  
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  duration = pulseIn(echo, HIGH);
  distance = (duration * 0.034)/2;
  frequency = map(distance, 2, 200, 2000, 200);
  tone(buzz, frequency);

  if (distance >= 150) {
    digitalWrite(red, LOW);
    digitalWrite(yellow, LOW);
    digitalWrite(green, HIGH);
  } else if (distance >= 75) {
    digitalWrite(red, LOW);
    digitalWrite(yellow, HIGH);
    digitalWrite(green, LOW);
  } else {
    digitalWrite(red, HIGH);
    digitalWrite(yellow, LOW);
    digitalWrite(green, LOW);
  }

  lcd.setCursor (11, 0);
  lcd.print (distance);  

}