from machine import Pin
from utime import sleep, ticks_us, sleep_us

triger=Pin(25, Pin.OUT)
echo=Pin(33, Pin.IN)
def ultra():
    triger.off()
    sleep_us(2)
    triger.on()
    sleep_us(5)
    triger.off()
    while echo.value()==0:
        signal_off=ticks_us()
    while echo.value()==0:
        signal_on=ticks_us()
    try:
        time_pass=signal_on - signal_off
    except NameError:
        return 0
    return timepass/58

red_pin = Pin(23, Pin.OUT)
yellow_pin = Pin(22, Pin.OUT)
green_pin = Pin(21, Pin.OUT)

while True:
    dist = ultra()
    print(f'Distance: {dist:.1f}cm')
    sleep(0.1)
    if dist <=50:
        red_pin.on()
        yellow_pin.off()
        red_pin.off()
    elif dist <=100:
        red_pin.off()
        green_pin.off()
        yellow_pin.on()
    elif dist <=200:
        yellow_pin.off()
        red_pin.off()
        green_pin.on()
    else:
        yellow_pin.off()
        red_pin.off()
        green_pin.off()