#include <LiquidCrystal_I2C.h>

#define I2C_ADDR 0x27
#define LCD_COLUMNS 20
#define LCD_LINES 4

int trigpin = 12 ;
int echopin = 11 ;
long duration, cm, inches;

int ledred=8;
int ledyellow=5;
int ledgreen=3;

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);

  pinMode(ledred, OUTPUT);
  digitalWrite(ledred, LOW);
  pinMode(ledyellow, OUTPUT);
  digitalWrite(ledyellow, LOW);
  pinMode(ledgreen, OUTPUT);
  digitalWrite(ledgreen, LOW);

  lcd.init();
  lcd.backlight();
  
}

void loop() {
  // put your main code here, to run repeatedly:
  
  digitalWrite(trigpin, LOW);
  delayMicroseconds(0);
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(0);
  digitalWrite(trigpin, LOW);

  pinMode(echopin, INPUT);
  duration = pulseIn(echopin, HIGH);

  cm = (duration/2) / 29.1;
  inches = (duration/2) / 74;

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  lcd.setCursor (1,0);
  lcd.print ("cm : ");
  lcd.setCursor(5,0);
  lcd.print (cm);
  lcd.setCursor (1,1);
  lcd.print ("in : ");
  lcd.setCursor(5,1);
  lcd.print (inches);

if (cm < 30) {
  digitalWrite(ledred, HIGH);
  delay(100);
  digitalWrite(ledred, LOW);
  delay(100);
}
if (cm > 30 && cm < 50) {
  digitalWrite(ledyellow, HIGH);
  delay(100);
  digitalWrite(ledyellow, LOW);
  delay(100);
}
if (cm > 50) {
  digitalWrite(ledgreen, HIGH);
  delay(100);
  digitalWrite(ledgreen, LOW);
  delay(100);
}

}