thermal_timer

m = peripheral.wrap("bottom")
timer = 460

function countdown()
  sum = timer
  for i = timer,0,-1 do
    m.setCursorPos(1,1)
    m.write(sum)
    sum = sum - 1
    sleep(1)
    m.clear()
  end
end


while true do
  redstone.setAnalogOutput("back",15)
  sleep(3)
  redstone.setAnalogOutput("back",0)
  countdown()
end