I remember from one of your other posts that in this case a "scanner" is a barcode scanner with an RS-485 connection.
Because RS-485 is a multi-drop electrical network technology, it is definitely possible to use multiple devices on a single RS-485 network.
The question is whether or not the protocol used by the barcode scanners is appropriate for a multi-device network.
If they are just sending out ASCII strings without being "polled" by a master device, there may be no automatic way to prevent multiple barcode scanners from transmitting at the same time, which would make the data corrupted. Making sure that only one scanner transmitted at one time would be a system configuration or function issue.
Or, if the barcode scanners do not identify themselves when they transmit, it may be more difficult to tell which scanner has transmitted.
Your other post made it sound like you are trying to use a controller that is too small, or avoid buying the appropriate I/O modules to perform the functions your system needs. I can't really give you advice other than to use a controller that has enough module capacity to perform the functions of the control system.
