from hcsr04 import HCSR04
from machine import Pin
led= Pin(5,Pin.OUT)
sensor = HCSR04(trigger_pin=4, echo_pin=15)
while True:
    distance= sensor.distance_cm()
    print('Distance', distance,'cm')
    if distance <20:
        led.value(1)
    else:
        led.value(0)