I need to be able to trigger a Pico to run a routine when a person walks past a museum display. I thought the best way of doing this was to implement a form of broken beam detection, ie to bounce a narrow beam of light from the device to a small mirror on a wall about 6ft away and back to a detector on the device. When someone walks by, the beam is broken, and the detector connected to the Pico triggers the routine. The coding is not a problem, but generating and detecting the beam of light is. The devices that can implement the beam generation of detection either:
A. have very limited range (measured in mm’s), or
B. quite expensive
Has anyone faced the same problem, if so how did you solve it?