I have been writing PLC programs for over 20 years. I often get asked what is the best way to lean PLC programming. Programming in the way I was taught in college was with the Motorola 6809. (Yes, I know that I am dating myself) This was microprocessor programming, but it was the best way to sometimes explain the methods behind PLC programming. Manufacturers of PLCs had allot of proprietary software that were not even related in their appearance and methods of programming. Today we have a few standards that have changed the look and feel of the programming software packages so each manufacturer is similar. The following is the best recommendation that I have for beginners to start to learn PLC programming today.
The first place to start in order to learn PLC programming is the free publication by Kevin Collins. This PDF will teach you PLC programming without just telling you what a PLC is and how it functions. He also includes some test questions along the way in order for you to retain and understand the important points that he is making.
PLC Programming for Industrial Automation
by Kevin Collins
(Note: This book is now for sale on Amazon.)
Topics covered include:
- PLC Basics
- Ladder Programming
- Conditional Logic
- Ladder Diagrams
- Normally closed contacts
- Outputs and latches
- Internal relays
- The Pulse Generator
- Sequential Programming Introduction
- Evolution of the Sequential Function Chart
- Programming using the Sequential Function Chart
- Entering the SFC program into the PLC
- Modifying an SFC Program
- Selective Branching
- Parallel Branching
After learning the basics from the above manual, practice. Create programs yourself and test what you have learned. You can accomplish this by using simulators. Allot of the programming software will have simulators. The simulator will mimic the PLC hardware so you can test your programs before installing in the field. Traditionally I have not been a fan of simulators, but recently Automation Direct has introduced a simulator with their Do-More PLC. It is the Do-More Designer Software. This software simulator includes the entire instruction set (Not Just Bit Logic) as well as communication protocols. It can be downloaded and installed for free from the above link.
The next step I recommend is then to advance into some of the advanced instructions. An understanding of the numbering systems in the PLC will be a benefit. Math, PID, register manipulation and conversion instructions are just a few of the advanced programming you can learn. All of these and more instruction information can be obtained from reviewing the documentation from the PLC manual that you are programming. Once again all of these instructions are included in the Do-More Designer Software.
Program structure is the next topic. Allot of programmers would stop here and can do well with developing software, however there is much more that you can lean. Sequencers give programmers the methods to change logic on the fly and allow troubleshooting the system easier. This method of programming can benefit you greatly and reduce the development time of your logic.
The last step that I recommend learning is the sharing of information. I am meaning the information that you program through an HMI and/or SCADA package. This refers to understanding of the ways in which information can be gathered from the PLC and displayed in different ways. Here are a couple of previous articles that have been written on this subject:
As you can see, there is allot of information available to you to begin and lean PLC programming without spending a dime! Remember that PLCs are similar to computers, (Moore’s Law) they increase in size and ability. Systems are expanding and changing everyday. Happy programming.
Do you know of additional tips or methods to share?
PLC Beginner’ s Guide – There are many different PLC manufacturers with different hardware and software. All of the programmable logic controllers have similar basic features. Here is how I would approach learning about basic PLCs.
Watch on YouTube : How you can learn PLC Programming without spending a dime!
If you have any questions or need further information please contact me.
If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.
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The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.