#include <Servo.h>

Servo lidServo;
const int trigPin = 9;
const int echoPin = 10;
const int servoPin = 3;

long duration;
int distance;

void setup() {
  Serial.begin(9600);
  lidServo.attach(servoPin);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  lidServo.write(0); // Lid closed initially
}

void loop() {
  // Ultrasonic sensor reading
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.println(distance);

  if (distance < 20) {  // Detect hand within 20cm
    lidServo.write(90); // Open lid
    delay(3000);        // Wait 3 seconds
    lidServo.write(0);  // Close lid
  }

  delay(500);
}