Interfacing PLC with ID System

I am currently working on a project that involves interfacing a PLC with a ID system such as barcodes or RFIDs. I am not sure how to begin. My project consists of reading a tag on a conveyor line that will signal a CPU to make a program change. The tag will have only a number burned on to it corresponding to a program number. The layout consists of as following: The ID reader will read a tag. The reader will send the tag number to a plc. The plc will send the number to a CPU that will then make the changes to the system.

Any ideas on what type of plc to use and the background on what format the program number is going to be in when it goes from machine to machine?

I presume the connection to the RFID is serial. If so, you could use Omron CS1 or CJ1 PLCs. They have inexpensive serial cards that mount in the processor (CS1) or rack (CJ1 and CS1). The CJ1 is really rackless and mounts on a DIN rail.

You would then require CX-Protocol software. This would enable you to very simply put together a serial communication to the RFID. They could probably supply the RFID as well with the protocol already written.

Access to the information collected in the serial card is very simply performed by the PMCR instruction in the PLC. Read the number and change the program to another task.

You can access any serial device in this way. I regularly access Modbus devices and GSM modems for SMS messaging.

The ID reader will read a tag. The reader will send the tag number to a plc. The plc will send the number to a CPU that will then make the changes to the system.

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What do you mean by this? Do you mean the PLC you're using has NO CPU????

I once simply connected a barcodereader to a serial port (CP521) in a Simatic S5-100U PLC and this little beggar did all the processing needed. When using an Allen-Bradley CompactLogix I don't even need a separate serial port, especially if I'm using an -L30 version. Because that version has two serial ports on board, I can program the darn thing while it's communicating with the barcode reader.

Kind regards,