#include <LiquidCrystal.h>
int trig_pin = A0;
int echo_pin = A1;
long echotime;
float distance;
LiquidCrystal lcd(0x27, 16, 2);
int buzzer = 13;
void setup() {
Serial.begin(9600);
pinMode(trig_pin, OUTPUT);
pinMode(echo_pin, INPUT);
digitalWrite(trig_pin, LOW);
lcd.begin(16,2);
pinMode(buzzer, OUTPUT);
}
void loop() {
// put your main code here, to run repeatedly:
digitalWrite(trig_pin, HIGH);
delayMicroseconds(10);
digitalWrite(trig_pin, LOW);
echotime = pulseIn(echo_pin, HIGH);
distance = 0.0001*((float)echotime*340.0)/2.0;
lcd.setCursor(0,0);
lcd.print(distance);
lcd.println(" cm");
delay(1000);
if (distance < 31) {
tone (buzzer, 1000);
delay (2000);
noTone (buzzer);
delay (500);
tone (buzzer, 1000);
delay (2000);
noTone (buzzer);
delay (500);}
}