from machine import pin
from time import ticks_us

relay = pin(12,pin.out)
sw = pin(18,pin.in,pin.pull_up)

isactive = false
start = ticks_ms()

while true:
     if ticks-ms()-start >= 300:
        if sw.value() == 0:
          isactive = not is active
          relay.value(is active)
      start = ticks_ms()