My Little Factory – April 2017
This post is the first in a series I am writing about a project I am working on, hence the “April 2017” designation. As most of my regular readers know, I have spent much of the past several years teaching …
Tag: Allen-Bradley
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! …
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 …
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 …
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 …
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 …
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, …
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 …
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 …
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 …