#include <Servo.h>  // Include the Servo library

#define SERVO_PIN 9   // Define the pin for the servo motor signal
#define LED_PIN 13    // Define the pin for the LED
#define TRIG_PIN 3    // Define the pin for the ultrasonic sensor trigger
#define ECHO_PIN 2    // Define the pin for the ultrasonic sensor echo

Servo servo;  // Create a Servo object to control the servo motor
int pos = 0;  // Variable to store the servo position

void setup() {
  pinMode(LED_PIN, OUTPUT);  // Set the LED pin as an output
  pinMode(TRIG_PIN, OUTPUT); // Set the TRIG_PIN as an output
  pinMode(ECHO_PIN, INPUT);  // Set the ECHO_PIN as an input

  servo.attach(SERVO_PIN);   // Attach the servo motor to pin 9

  Serial.begin(9600);        // Initialize serial communication for debugging
}

void loop() {
  // Trigger the ultrasonic sensor to send out a pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read the pulse duration from the sensor
  float duration_us = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance in cm
  float distance_cm = 0.017 * duration_us;

  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  if (distance_cm < 20) {
    // Rotate the servo from 0 to 45 degrees
    for (pos = 0; pos <= 45; pos += 1) {
      servo.write(pos);  // Move the servo to the current position
      delay(10);         // Wait 10ms for the servo to reach the position
    }
    delay(500); // Add delay after reaching 45 degrees
    digitalWrite(LED_PIN, HIGH);  // Turn on the LED when the servo is at 45 degrees
  } else {
    // Rotate the servo from 45 to 180 degrees
    for (pos = 45; pos <= 180; pos += 1) {
      servo.write(pos);  // Move the servo to the current position
      delay(10);         // Wait 10ms for the servo to reach the position
    }
    delay(500); // Add delay after reaching 180 degrees
    digitalWrite(LED_PIN, LOW);   // Turn off the LED when the servo is at 180 degrees
  }

  delay(1000);  // Additional delay before the next loop iteration
}