Driver for Allen-Bradley PLCs


Thread Starter

Juan de Arajo

Does anybody know if exists a driver to comunnicate Visual Basic with Allen-Bradley's PLCs without use RSLinx ?


Juan de Arajo
There are a couple (ocx) controls and dll's available on the internet. The problem is, they are usually pretty expensive. Atleast I think so. If you're interested in developing your own control, I'd suggest reading the book "Home Automation Basics" by Thomas E. Leonik. It's going for about $25.00 at It will show you how to develop a communication protocol (for a micrologix), and get you started in the right direction if you should want to develop your own control. The code is all in VB 6, and explained thoroughly.
There is a file called SLCComm.ocx that can be downloaded from

It will communicate with SLC 5/04 and MicroLogix.
It is an evaluation package but only costs $35.00
to purchase. It comes with a help file and an example VB project that will show you how to use the control.


Michael R. Batchelor

Yes, we've used it quite a bit. For a small project it works great. And you can compile and distribute royalty free.

For a large project it's got a lot of overhead and has a few quirks that are maddening. Plus it's not able to coexist with RSLinx using a KTX card or serial port, so be careful if you want
to do anything else with the machine. I don't know if we've ever tried to use both simultaneously with an Ethernet PLC, but I'll
ask one of the guys if your interested.

I've heard good things about their OPC server, but it requires a seperate license for each and every PC it's installed on, much like RSLinx would require. So far, all of our customers have
opted for RSLinx.

Michael R. Batchelor - Industrial Informatics & Instrumentation, Inc.
Linux is like a wigwam...
No windows, no gates.
Apache inside.
Typically when purchasing OPC servers, you only have to pay for the license for the one that is used on the computer that is doing the development (on VB, C++ or whatever your doing the development on). You do not have to purchase a separate license for each computer you are running your developed executable file.
A number of companies make ActiveX components to communicate with AB PLC's. Search the web. Or look at Software Toolbox, Cimquest, or Automated Solutions. (and probably others)

Bill Sturm

This statement about licensing is generally inaccurate as it relates to OPC servers. You can purchase ActiveX controls for connecting VB/VC++ to OPC servers (i.e. that do not require any deployment licenses but the OPC server part itself usually requires a per machine license. I know it to be this way for OPC server licensing with Kepware, Matrikon, Cimquest,
Automated Solutions, Intellution, Wonderware, Rockwell, Software Toolbox, Merz, Softing and many other providers of OPC servers.

There are ActiveX controls available for communications for which you can purchase a development license for each development computer but do not need to purchase per machine deployment licenses for. Companies such as Cimquest, Software Toolbox, Automated Solutions, and Parijat offer these types of solutions.

Each approach to communications with VB has its relative merits based on the application requirements of the user, alas that is another topic for another day and another post.

John Weber