Sensor... Which one should I use?

Other Hardware Sensors
5

:wink:
well definitely will not work in the dark.

There are IR optical devices that may well satisfy your needs ... I use 'em on homemade clocks ... wave my hand to change the display mode.

https://www.amazon.com/XLX-TCRT5000L-Photoelectric-Reflective-Transistor/dp/B01N2HVRQP/ref=sr_1_6?keywords=ir+phototransistor&qid=1637593384&sr=8-6