from machine import pin
import time
merah=pin(18,pin.out)
kuning=pin(19,pin.out)
hijau=pin(21,pin.out)

def traffic():
    merah.on()
    time.sleep(3)
    merah.off()
    kuning.on()
    time.sleep(1)
    kuning.off()
    hijau.on()
    time.sleep(5)
    hijau.off()

while True:
    traffic()