Yes, I agree —— I have definitely worked with many different brands of printers and I can recall that many of them does not have their fans change on/off state as the extruder temperature changes. I will change my device right away so that it can measure the extruder temperature on its own and does not rely on any fans. However, the changes this device will bring remain the same: You get to do extra printings when not watching the printer, which gives you more efficient use of the printer without worrying about it even when you are not watching. Also, when someone once again attempts to lecture you on the significance of environmental protection and in general, sustainable development, you'll get to reply "but I AM practising it right now" by showing them the 3d Printer's Auto-off Switcher.
You can send me an email through wuyukun89@163.com so that after I updated the device again, I can send you its pictures and its demonstration videos. If you have any questions about this product, you can always ask me.
P.S. The "PS" in your replied post stands for Power Supply, doesn't it? I'll just explain it for anyone who's reading our posts and haven’t figured it out yet☺.