Programming Techniques

Here are a couple of presentations I run in class regarding PLC programming techniques and factoryio. The exercises are first done via the Whiteboard to encourage the Students to take notes and pay attention to the details. ​

Basic PLC Texts have their advantages but also come with limitations. Many that I have read take a look at basic hardware configurations and concentrate on Boolean Algebra, Logic Gates and Conversion to Ladder. Mostly this is due to the introductory nature of the material. Although good basic foundations for Logical Systems, most of this has very little to do with Programming Machines or Automation on a Factory Floor. The techniques I discuss include building a simple program covering Automatic and Manual Modes as well as ideas for Cycle Start and End of Cycle. Also discussed are simple Faults, their meaning and possible application.

PLC Programming Techniques - Part 1.pdf (283.7 KB)
PLC Programming Techniques - Part 2.pdf (570.4 KB)

You may view and print, but not edit these files for the time being as they are preliminary and may be updated in the future.


Thanks for sharing, great materials! :+1:

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Can you tell me why ladder is so much used in the U.S.? I have the feeling European companies are using text based languages much more than the U.S., or is this just my impression?

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Janbumer1: That is a great question. My experience is primarily with the Automotive Industry; however, I have worked with OEM’s from around the world over the years. General Motors has always been innovative and the Engineers willing the take risks. With that being said, we have experimented with other programming techniques such as Statement List, Sequence Diagrams and Flow Charting but always seem to come back to Standard Ladder for Basic Machine Control. The ease of visualization (power flow) does seem to help make Ladder more understandable to a wide variety of Personnel on the shop floor. Since our equipment is purchased from all over the world, Ladder is a platform that is common regardless of PLC / CNC / Robot manufacturer. This helps reduce confusion between departments and training costs overall. Sure, an Electrician / Technologist can become quite adept at other languages, and those may even be better in some fashion, but once personnel move to another department or piece of equipment, they would have to learn a new language. In a lean manufacturing environment, where reducing Mean Time to Repair is critical to success, Ladder just seems to be a good base.

Well, I have seen a lot of code in FBD or IL around here. That is more or less the standard and the people that are allowed and have the equipment to take a look into the PLC and thus the program are normally trained enough to understand the language.
What I have seen is that even stuff that has no reason to be done in ladder like TCP-connections, visualisation stuff, data handling and other more complicated stuff than “I0.0 AND I0.1 = Q0.0” is done with ladder. This seems a little counterproductive in my mind. I have done the comparison between FBD, IL and ST for some data handling or communication functions, and I gotta say you save a lot of time AND are less complex with ST than with FBD or IL.
I think maintenance on the floor shouldn’t have to look into the PLC program. Your code should either be robust enough or your visualisation/error codes should be detailed enough that the operator or someone from maintenance can get the machine running again without a laptop most of the time. We have machines that are running for years without us getting a call to check into the code.

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