Automatic Power Off after print

Hi!

How about automatic powering off your printer when printing is done?
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>*Update! New, better, safe version is published. Go there for it!
https://www.thingiverse.com/thing:3335522

I want to share my upgrade for 3D printer which gives Auto Power Off functionality.
Some printers, equipped with ATX PSU may do this by simple M81 command. Lucky owners!!!!
All others, or almost all others, know these timers to switch off the printer