Simple PC - PLC Communications Part I

A simple PC application structure that communicates to PLC

In most cases PLC is enough to solve automation tasks with its programming interface and special designed architecture.

However, it is not always possible to solve all problems such as database support. Some PLC brands have command sets supporting table search but it is not intended for complex operations.

In this post, we will focus on a PC application that supports PLC by exchanging data.

Most common PC – PLC communication methods are RS 232 and Ethernet, they do not differ in
basic software structure, so you can apply this structure for both RS232 and Ethernet communications. Also it is possible to use parallel hardware I/O cards on PC for communication, the same structure also fits for I/O cards.

The most convenient way for communicating is continuously exchanging snapshots of memory areas between PC and PLC.

Actually, all PLC systems do the same thing at the background:

Reading inputs, evaluating them to calculate necessary outputs and writing outputs continuously in a loop.

If we adopt this to a PC application, same algorithm could be as follows:

This structure simplifies PC evaluation algorithm.

Next post is going to be a simple case study, we will design a station that gives feedback to PC for
recording a products information to maintain traceability.

First Post

This is the very first post, I hope we will share lots of experience in this blog.

I am an automation engineer and using PC for many industrial automation problems.

In da notes stands for 'Industrial Automation Notes' and I am planning to publish some of my experiences as case studies in this blog. As I said, my favourite tool is PC for automation, so probably you will find more tips and trics with PC.

However, automation without PLC is impossible, for that reason this blog will contain example applications with PC and PLC.

If you are also an automation guy, you should be so busy and can understand me if I can't feed this blog so frequently. All experiences from readers are wellcome.

I am planning to post tutorials from simple to complex, this structure requires references links to older posts. Probably my second post will be about simple PC - PLC communication basics.

I offer you to subscribe this blog to be informed on new posts because I may not feed so frequently. Unfortunately you may fed up checking this blog without any new posts, so it should be better to subscribe.

See you in next post !