#bai2
from hcsr04 import HCSR04
from machine import Pin
sensor = HCSR04(trigger_pin=15, echo_pin=4)
led1 = Pin(2, Pin.OUT)
led2 = Pin(5, Pin.OUT)
led3 = Pin(18, Pin.OUT)
while True:
    distance = sensor.distance_cm()
    if distance < 20:
        led1.on()
        led2.off()
        led3.off()
    elif distance < 30:
        led1.on()
        led2.on()
        led3.off()
    elif distance < 40:
        led1.on()
        led2.on()
        led3.on()
    else:
        led1.off()
        led2.off()
        led3.off()
    print('Distance: ', distance, 'cm')