#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);
int trigger = 12;
int echo = 11;
int time = 0;
int distance = 0;
int pinR = 3;
int pinG = 4;
int pinB = 5;

void setup() {
  // put your setup code here, to run once:
  pinMode(echo, INPUT);
  pinMode(trigger, OUTPUT);
  lcd.init();
  lcd.backlight();
  Serial.begin(9600);
  lcd.begin(16,2);
  pinMode(pinR, OUTPUT);
  pinMode(pinG, OUTPUT);
  pinMode(pinB, OUTPUT);
}

void loop() {
  lcd.clear();
  digitalWrite(trigger, LOW);
  digitalWrite(trigger, HIGH);
  time = pulseIn(echo, HIGH);
  distance = (time*0.0172);
  lcd.setCursor(5, 0);
  lcd.print(distance);
  lcd.print("cm");
  delay(1000);
  if(distance <= 20) {
    digitalWrite(pinR, HIGH);
    digitalWrite(pinG, LOW);
    digitalWrite(pinB, LOW);
  } else if(distance <= 40) {
    digitalWrite(pinR, LOW);
    digitalWrite(pinG, HIGH);
    digitalWrite(pinB, LOW); 
  } else {
    digitalWrite(pinR, LOW);
    digitalWrite(pinG, LOW);
    digitalWrite(pinB, HIGH);
  }
}