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THE DEVIL SUGGESTS

Make a device that complains when you leave a light on

Unnecessary · Use what you have · Easy

Build a mildly judgemental gadget that notices a light has been left on and voices an opinion. Keep it charming enough that you do not immediately unplug it.

Do it

  1. Choose a safe way to detect light, such as a light sensor.
  2. Connect the sensor to a small controller.
  3. Pick a buzzer, screen or speaker for the complaint.
  4. Set a delay so it does not react to every passing shadow.
  5. Test it in one room and tune its level of annoyance.

What next?

Keep the useful notes, photograph the result if there is one, then go and find something else to do.