from machine import Pin
from time import sleep

ledRojo_pin     = 21
ledAmarillo_pin = 22
ledVerde_pin    = 23

ledRojo     = Pin(ledRojo_pin , Pin.OUT)
ledAmarillo = Pin(ledAmarillo_pin, Pin.OUT)
ledVerde    = Pin(ledVerde_pin , Pin.OUT)

while True:
    ledRojo.value(1)
    ledAmarillo.value(0)
    ledVerde.value(0)
    sleep(3)

    ledRojo.value(1)
    ledAmarillo.value(1)
    ledVerde.value(0)
    sleep(3)

    ledRojo.value(0)
    ledAmarillo.value(0)
    ledVerde.value(1)
    sleep(3)

    ledRojo.value(0)
    ledAmarillo.value(1)
    ledVerde.value(0)
    sleep(3)