[Need help] Rectangular Area Detection

Hi all,

I am new in this forum and I wish to find help.

I have a rectangular area and I am looking for a set of components (i.e Sensors ) to detected if the object inside this area or not.

The output of the circuit should be suitable for a programming language.

I want to connect and program the circuit to a basic stamp parallax training kit.

Any idea, please help!

Thanks in advance.

My2k

what is the area size, object size and type, environment, etc.