Blog Archives

Birth of the Programmable Controller

Today’s post is extracted from my new “generic” PLC course manual, PLC Hardware and Programming – Multi-Platform. In the manual, I also cover the origins of the computer, beginning with the Babbage Analytical Engine, all the way back in 1823!

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Posted in PLCs

Ladder Logic 305: ASCII and Strings

Today’s post covers ASCII, string manipulation and how to deal with readable text in a PLC. The picture above is from a ControlLogix program (Allen-Bradley, RSLogix5000 v.16) I wrote back in 2006. The program communicated with a PC-based Cognex machine

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Posted in PLCs, Software & Programming, The Book

Tag Structures and Dotfields

Today’s post is in response to an e-mail I received asking for my thoughts on Tag Structure. In part, George Steel wrote: Great site, thanks for all your efforts. I am working on positioning my org to move from RS500

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Posted in Controls Design, Documentation, Software & Programming

PLC Memory

As I have mentioned previously, I have been working on a generic PLC course that I hope to release in some kind of online software format soon. I was able to test a prototype a few weeks ago with a

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Posted in PLCs, Software & Programming, The Course

Request for PLC Information and Samples

I mentioned last week that I am working on what I believe is the first truly advanced non-platform-specific book on PLC Programming. My friend Tony over on Factory Automation Software Blog has reviewed some books that come the closest, but

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Posted in PLCs, Software & Programming, The Book

Ladder Logic 105: PLC Scanning

In my last post on PLC Memory Organization, I mentioned that I had not really covered how scanning actually works in a programmable controller. This is certainly a topic that needs to be discussed for an understanding of PLC programming,

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Posted in PLCs, Software & Programming

Ladder Logic 104: Memory Organization

One of the first decisions that needs to be made when designing a PLC system is memory allocation and organization. In the early years of the PLC memory came at a premium… 1K (one kilobyte) of memory for the program

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Posted in PLCs, Software & Programming

Ladder Logic 304: Timer Application

Today’s post is in response to Dave Tompkins, who posted a request for help last week for an application. Since he posted it on one of my series posts on ladder logic (204: Auto Sequences) I decided to frame it

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Posted in Applications, PLCs, Software & Programming

Non-Native Devices: .eds and .gsd files

When designing a control system, sometimes it becomes necessary or advantageous to communicate with devices that were not made by the PLC manufacturer. If these devices need to be placed on an Ethernet, DeviceNet or Profibus network there are methods

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Posted in Integration, PLCs, Software & Programming, Vendors and Manufacturers

Ladder Logic 303: PLC Forensics

Today’s topic involves a project I have been working on over the last few months. The project consists of adding process equipment including tanks, pumps, valves and instrumentation to an existing system… while it is running. Because production runs 24

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Posted in Integration, PLCs, Software & Programming
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