Wireless Light Switching

My student room did not have a regular light switch, thus I made a system which enables wireless switching. You can do this by waving your hand (or any object) in front of the sensor at a set distance. This was made using a supersonic distance sensor, a microcontroller (Arduino) with some simple code, a relay and some accomodating circuitry & soldering. It has been operational and safe since 2021. Fun fact: due to the nature of the sensor one can also switch using any supersonic (40kHz) sound source such as keys! Bug or feature? ;)