SoftLogix 5800 and VBA Data Collection

[edward2 0]

I have setup several Data Collection Systems in the past using VBA code to read "data" from a ControlLogix processor via a DDE/OPC topic, and put it into an ACCESS database. The ControlLogix PLC would save 10-30 minutes worth of data, and then the VBA code would run every 10-30 minutes to retrieve the data and put it into the database. I'm now looking at a project that has two SLC500 PLCs and one CompactLogix PLC. I was thinking about using SoftLogix 5800 on my data collection computer to gather all of the "data" from the other PLCs, and store about 30 minutes worth of the data. Then the VBA code could read the data from the SoftLogix PLC and put it into the database. One of the reasons that I am considering this is that I don't want to make any changes to the three PLCs, since they were supplied and programmed by another company. Has anyone done this, and do you have any suggestions and/or comments? I assume that I could still use a DDE/OPC topic to communicate with the SoftLogix processor. Thanks,

[paulengr 44]

You can, BUT.... Access databases will eventually become corrupt. It's in the nature of the JET SQL engine to do this. A quick google search will reveal just how bad the problem is. In a word, don't use it or you will eventually be disappointed. DDE is officially obsoleted by Microsoft. It's also not very stable in the first place. You can still get it to work at least up to Windows XP but beyond that it's getting dicey. Also it occasionally crashes no matter what the OS. Hence the reason that DDE was abandoned years ago by most folks. OPC is also officialy obsoleted because the whole COM/DCOM object model is as well. Right now it's still supported in as far as you can still use software out of the box without loading a special driver (unlike DDE) but it's days are numbered. This is one of the big drivers for OPC-UA. Similarly, VBA is officially obsoleted. Again, it's still there inside Microsoft Office and there's sort of a "legacy support" for 3rd party products last I knew, but the writing is clearly on the wall. If you want to get off the "obsoletion/daily patch" tread mill, get away from ANYTHING Microsoft produces. Check out Ignition from Inductive Automation. At it's heart, it already has the data logger and it's based on a stable SQL platform. It probably does everything you want already. Even if you don't use Ignition, their OPC-UA server/client is free and bypasses the entire OPC/DDE issue. High quality SQL servers are available all over the place as well for free, even Microsoft SQL Server. If you haven't used any others and there's no pressing need for a specific one, I recommend PostgresSQL for a "big" version, or one of the many Java embedded versions for a "local" one.