import time
from machine import Pin
from hcsr04 import HCSR04

led = Pin(0,Pin.OUT)
sensor = HCSR04(trigger_pin=18, echo_pin=19, echo_timeout_us=1000000)

while True:
    distance = sensor.distance_cm()
    print(distance,'cm')
    time.sleep(0.5)
    a = distance / 100

    if distance <= 200:
        led.value(1)
        time.sleep(a)
        led.value(0)
        time.sleep(a)