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 after printing is finished. We also know that expected finishing time may be different than calculated by slicer software. So we add one or two hours to not switch off the printer too early.
I started to be tired of this solution and invented my way of secure switching off the printer just after the printing. Tested with Ender 3. Should work with similar printers.
After finishing printer cools down and raises printhead frame to the maximum height. It triggers switch and disconnects power fr