//BY IRFXN.ISMAIL-ADAM IZZAT-ZAFRAN
#include <Servo.h>
#define TRIG_PIN 3        // The Arduino Nano pin connected to the TRIG pin of the HC-SR04
#define ECHO_PIN 2        // The Arduino Nano pin connected to the ECHO pin of the HC-SR04
#define SERVO_PIN 9 

float duration_us, distance_cm;
Servo servo; 

void setup() {
  // Begin serial communication
  Serial.begin(9600);

  // Configure the trigger pin as an output
  pinMode(TRIG_PIN, OUTPUT);

  // Configure the echo pin as an input
  pinMode(ECHO_PIN, INPUT);

  servo.attach(SERVO_PIN);
}

void loop() {
  // Produce a 10-microsecond pulse to the TRIG pin
  digitalWrite(TRIG_PIN, LOW);  // Set the TRIG pin low for a short time to ensure a clean pulse
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH); // Set the TRIG pin high for 10 microseconds to generate a pulse
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);  // Set the TRIG pin low again

  duration_us = pulseIn(ECHO_PIN, HIGH);
  distance_cm = 0.01715 * duration_us;

  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

if(distance_cm < 20)
{
servo.write(45);
}

else {
  servo.write(180);
}

  delay(100); // Delay 500 milliseconds before the next measurement
}