#include <Wire.h>
#include<LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);
const int triggerPin_1 = 13;
const int echoPin_1 = 12;
unsigned int duration_1;
unsigned int distance_1;
const int triggerPin_2 = 11;
const int echoPin_2 = 10;
unsigned int duration_2;
unsigned int distance_2;
const int triggerPin_3 = 9;
const int echoPin_3 = 8;
unsigned int duration_3;
unsigned int distance_3;
const int triggerPin_4 = 7;
const int echoPin_4 = 6;
unsigned int duration_4;
unsigned int distance_4;
void setup() {
  
  pinMode(triggerPin_1, OUTPUT);
  pinMode(echoPin_1, INPUT);
  pinMode(triggerPin_2, OUTPUT);
  pinMode(echoPin_2, INPUT);
  pinMode(triggerPin_3, OUTPUT);
  pinMode(echoPin_3, INPUT);
  pinMode(triggerPin_4, OUTPUT);
  pinMode(echoPin_4, INPUT);
  Serial.begin(9600);
  }
void loop() {
  readSensor_1();
  readSensor_2();
  readSensor_3();
  readSensor_4();
  Serial.println(" ");
  delay(1000);
}
void readSensor_1() {
  digitalWrite(triggerPin_1, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin_1, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin_1, LOW);
  duration_1 = pulseIn(echoPin_1, HIGH);
  distance_1 = (duration_1 / 2) / 28.5;
  Serial.print("Sensor 1 = ");
  Serial.print(distance_1);
  Serial.println(" cm");
  if(distance_1<=100)
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("HERE IS EMPTY!!");
}
void readSensor_2() {
  digitalWrite(triggerPin_2, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin_2, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin_2, LOW);
  duration_2 = pulseIn(echoPin_2, HIGH);
  distance_2 = (duration_2 / 2) / 28.5;
  Serial.print("Sensor 2 = ");
  Serial.print(distance_2);
  Serial.println(" cm");
  if(distance_2<=101-200)
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("HERE IS EMPTY!!");
}
void readSensor_3() {
  digitalWrite(triggerPin_3, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin_3, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin_3, LOW);
  duration_3 = pulseIn(echoPin_3, HIGH);
  distance_3 = (duration_3 / 2) / 28.5;
  Serial.print("Sensor 3 = ");
  Serial.print(distance_3);
  Serial.println(" cm");
  if(distance_3<=201-300)
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("HERE IS EMPTY!!");
}
void readSensor_4() {
  digitalWrite(triggerPin_4, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin_4, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin_4, LOW);
  duration_4 = pulseIn(echoPin_4, HIGH);
  distance_4 = (duration_4 / 2) / 28.5;
  Serial.print("Sensor 4 = ");
  Serial.print(distance_4);
  Serial.println(" cm");
  if(distance_4<=301-400)
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("HERE IS EMPTY!!");
}