A nice way to protect your and your guests' privacy with a red led that flashes when the door is closed!

The objective was to put, instead of the key, the circuit and the battery inside the door, leaving visible just a small magnet.

The use of the microcontroller and the related code allow to minimize the current consumption, which is about 3 mA for 30 ms with LED on, about 5 µA with LED off, and zero when the magnetic switch is open. The battery will therefore last  hundreds of hours.

In case you don't like the idea, a very small and low-power LED flasher will reamain anyway!

I've attached some pictures, schematic, the sketch and the firmware of the project and a short demo video.

Best regards,