S7300 comms to VB

I have an application which is written in VB. It is a sequencial operation however and struggles with the sequence.

I am proposing to put in a PLC to take control of the sequence and control logic but leave the VB visualisation intact. To do this however, I need to know how to access data in the PLC via VB. Has anyone done this? Thanks,

Hi Stuart.

Look at Libnodave which is freeware.

That, or go the full OPC way, which may be easier than one might fear.
You will need an OPC server for Siemens, and you will need an OPC Client wrapper for VB. For that part look here:
http://www.opcconnect.com/complib.php
here is one that looks good for VB (ignore the cheesy layout of the site): http://www.opcware.com/OPCWare.html .

Anyway, I commend you decision to move any sequencing program away from VB and putting it in a PLC.

Thanks,

I will check out those links. Have you used OPC in VB before is it akward? Im not entirely sure what the first package does. I will have a look tomorow