a small lua file to make an ESP01 turn on a relay for 20 minutes then off for 20 minutes and repeat.

init.lua

-- luacheck: globals gpio tmr

gpio.mode(3, gpio.OUTPUT) -- GPIO0
gpio.write(3, gpio.LOW)
-- gpio.mode(4, gpio.OUTPUT) -- GPIO2

local TWENTY_MINUTES = 20 * 60 * 1000
local THIRTY_MINUTES = 30 * 60 * 1000
local SIXTY_MINUTES = 60 * 60 * 1000


local on

local function off()
    print("off")
    gpio.write(3, gpio.HIGH)
    local t = tmr.create()
    t:register(TWENTY_MINUTES, tmr.ALARM_SINGLE, on)
    t:start()
end

on = function ()
    print("on")
    gpio.write(3, gpio.LOW)
    local t = tmr.create()
    t:register(TWENTY_MINUTES, tmr.ALARM_SINGLE, off)
    t:start()

end

print("starting")
on()