from machine import Pin, PWM
from time import sleep
from hcsr04 import HCSR04

sensor = HCSR04(trigger_pin=4, echo_pin=15)
servo_pin = Pin(18)
servo = PWM(servo_pin, freq=50)

def open_door():
    servo.duty(1023)
    sleep(1)

def close_door():
    servo.duty(0)
    sleep(1)

while True:
    distance = sensor.distance_cm()
    if distance <= 50:
        open_door()
    if distance > 50:
        close_door()