Press the "hour" "minute" and "second" button separately to set the countdown time, then the screen shows "ON". Press the "start/restart" button to start work. For example: need to set the expose time 5 minutes 30 seconds.
Ress "C" button to remove the original set. Press "minute" set to "5"; press "seconds" set to "30"; Then press "start/restart" to start machine, light on. After 5 minutes 30 seconds, light will turn off automatically. If this setting do not need to be changed, it will be saved automatically. When the machine start again, timer will start again from 5 minutes and 30 seconds.