#include <LiquidCrystal.h> 
 
const int rs=13,en=12,d4=10,d5=7,d6=6,d7=5; 
LiquidCrystal lcd(rs,en,d4,d5,d6,d7); 
int buttonState=0; 
 
#define trigPin 2 
#define echoPin 3 
#define ledGreen 8 
#define ledYellow 9 
#define alarm 11 
 
int range=2; 
 
void setup() { 
  Serial.begin(9600); 
  pinMode(trigPin,OUTPUT); 
  pinMode(echoPin,INPUT); 
  pinMode(ledGreen,OUTPUT); 
  pinMode(ledYellow,OUTPUT); 
  digitalWrite(ledGreen,HIGH); 
  digitalWrite(ledYellow,LOW); 
 
  pinMode(4,INPUT); 
  lcd.begin(16,4); 
 
} 
 
void loop() { 
  long duration, inches, cm; 
  digitalWrite(trigPin,LOW); 
  delayMicroseconds(2); 
  digitalWrite(trigPin,HIGH); 
  delayMicroseconds(5); 
  digitalWrite(trigPin,LOW); 
 
  duration=pulseIn(echoPin,HIGH); 
 
  inches=microsecondsToInches(duration); 
  cm=microsecondsToCentimeters(duration); 
 
  Serial.print(inches); 
  Serial.print("in, "); 
  Serial.print(cm); 
  Serial.print("cm"); 
  Serial.println(); 
 
   
  delay(200); 
 
  buttonState=digitalRead(4); 
  if(buttonState==HIGH) 
  { 
    lcd.clear(); 
    lcd.setCursor(0,0); 
    lcd.print("ALARM ON"); 
    lcd.setCursor(0,1); 
    lcd.print("SAFE"); 
    if(inches<range) 
  { 
    Serial.println("DANGER"); 
    lcd.setCursor(0,0); 
    lcd.print("ALARM ON");
    lcd.setCursor(0,1); 
    lcd.print("DANGER");
    digitalWrite(ledGreen,LOW); 
    digitalWrite(ledYellow,HIGH); 
    tone(alarm,2000); 
    delay(100); 
  } 
  else 
  { 
    Serial.println("GOOD"); 
    digitalWrite(ledGreen,HIGH); 
    digitalWrite(ledYellow,LOW); 
    noTone(alarm); 
    delay(100); 
  } 
  } 
  else 
  { 
    lcd.clear(); 
    lcd.setCursor(0,0); 
    lcd.print("ALARM OFF"); 
    
    Serial.println("GOOD"); 
    digitalWrite(ledGreen,LOW); 
    digitalWrite(ledYellow,LOW); 
    noTone(alarm); 
    delay(100); 
   
  } 
 
} 
long microsecondsToInches(long microseconds) 
{ 
  return microseconds/74/2; 
} 
long microsecondsToCentimeters(long microseconds) 
{ 
  return microseconds/29/2;
}