#include <Servo.h>
#define SERVO_PIN 18

Servo servoMotor;

servoMotor.attach(SERVO_PIN);

const int trigPin = 4;
const int echoPin = 2;
const int buzzer = 12;
const int ledPin = 13;

long duration;

int distance;

int safetyDistance;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  safetyDistance = distance;
  if (safetyDistance <= 20) {
    for (int pos = 0; pos <= 180; pos += 1) {
      servoMotor.write(pos);
      delay(15);
    }
    digitalWrite(ledPin, HIGH);
  }
  Else {
    for (int pos = 180; pos >= 0; pos -= 1) {
      servoMotor.write(pos);
      delay(15);
    }
    digitalWrite(ledPin, LOW);
  }
  Serial.print("Distance: ");
  Serial.println(distance);
}