Good morning,
I would like to build a system that turn on a LED when inside a room there are a maximum number of persons. The led is outside the room in way that if a person look at the led and see it on doesn’t enter inside.
To achieve this task I yet developed the system inside with an Arduino board and a camera. For the LED outside I need a radio module able to communicate with a radio master connected with Arduino inside the room and able to turn on the LED standalone (without any other control boards (e.g. Arduino). This is necessary because the system outside should to be able to work with a battery for some months without charging or replacing.
Radio frequency communication is preferred than WiFi to avoid connection with external infrastructure.
Which is the best module that I could buy for this function?
Thankyou in advance for your precious and appreciated support.