Need Ideas

The ActiveX control will work and allow you to write the data directly from the VB app into the memory of the 90-30. If this is acceptable, you should only have to modify the VB app to point to the memory location that you want to change. Is the Wonderware also hitting the 90-30? If it is, are you talking via Ethernet or RS485? If you are using Ethernet, two devices hitting the port should not be a problem. If you are talking RS485, then two devices on the same network and timing may be an issue.

If this is the case, a cleaner solution would be to setup a small SQL DB table that the VB app and the Wonderware can hit. Then, using SQL instructions with InTouch, you could check the table and when the VB app sets the bit or writes the word that says everything is OK, Intouch would set the appropriate bit in the PLC.

Hopefully, you will be talking Ethernet and the ActiveX control will work for you. I would be a lot less code.

Regards

If I go the SQL route would there be any problems if I poll the database every second. If there are no problems going this way it'll be alot cheaper than going with the ActiveX control.

Intouch and the PLC are communicating over ethernet.

How is the VB application communicating with the Reliance PLC? If it is over an RS232 or RS485 serial link, what protocol is it using? If it is currently using Modbus, the change should be pretty easy.

It should not be a problem to hit the SQL DB every second, especially if the InTouch and VB app reside on the same PC or server. Going this route will require much more code, though. Not only will you have to program the InTouch app to hit the DB with SQL statements, you will also need to be able to use ADO or ADO.net, depending on the version of VB you are using.. Not to mention, you will also have to configure the SQL DB table.

If you already have the VB 6.0 or VB.net and the SQL DB, it would be cheaper than the ActiveX control, but it is a task that will take some time and effort. The quickest, easiest way out is to spend the money and get the VB ActiveX.Control.

Good Luck

How about polling an access database every second?

My experience with Access is that it would be a bad idea. Access just isn't optimized for speed like SQL Server is and if you are connecting to the data base remotely, you could have even worse perfomance. The good thing is that the DB table would not be very large, so you could write the code and build the Access DB and give it a try. With ADO or ADO.net, switching to a SQL DB after the code has already been written would be relatively easy as long as you have designed both data bases properly. In fact, it may be as simple as changing your connection string in VB, depending upon how you write the code and develop both data bases. I still like you ActiveX idea!

OK thanks for the suggestions , I will probaly go the ActiveX route beacuase of ease and the time saved programming will pay for cost of activex.