#include <Servo.h>

const int triggerPin = 9;
const int EchoPin = 10;
const int ServoPin = 3;
Servo servo;

const int DetectDistance = 20; 
const int delayTime = 20000;     
const int GapTime = 6000;         


void setup() {
  pinMode(triggerPin, OUTPUT);
  pinMode(EchoPin, INPUT);
  servo.attach(ServoPin);
  servo.write(0);
}

void loop() {
  if (isObjectDetected()) {
    delay(delayTime);
    for (int i = 0; i < 3; i++) {
      moveServo();
    }

  }
}

bool isObjectDetected() {
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  long duration = pulseIn(EchoPin, HIGH);
  int distance = duration * 0.034 / 2;
  return (distance > 0 && distance <= DetectDistance);
}

void moveServo() {
  servo.write(90); 
  delay(5000);    
  servo.write(0);  
  delay(5000);   
}