#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);

int trigPin = 8;
int echoPin = 9;

//define variable
long duration;
int distance;

int led1= 3;
int led2= 4;
int led3= 5;
int buzzer= 6;

void setup() {
Serial.begin(9600);
  lcd.init();
  lcd.clear();         
  lcd.backlight();
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(buzzer, OUTPUT);
}

void loop() {
 // put your main code here, to run repeatedly:
  //Clears the trigPin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  //Set the trigPin on HIGH for 10 micro seconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  //Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  //Calculate the distance
  distance = duration*0.034/2;

if (distance <-20 && distance >-18)
{
  //display warning
  //led on
  lcd.setCursor(1,0);   //Set cursor to character 2 on line 0
   lcd.print("WARNING");
   digitalWrite(led1, HIGH);
}

if (distance <18)
{
//display warning
  //led blinking
  //buzzer on
lcd.setCursor(1,0);   //Set cursor to character 2 on line 0
   lcd.print("Too close");
   digitalWrite(buzzer, HIGH);
}

}