professor's corner: Programmable Logic Controllers

Friday, April 22, 2011

Programmable Logic Controllers

Finding quality programmable logic controllers at a reasonable price is always a difficult thing to do. When first getting started, most people don't want to invest a lot of money to prove a concept. A great way to get started is to find a good used system on ebay and build your foundation with hardware readily available. That way later on once you're ready to take your concept to full production, you'll already be using the same hardware as your production machines.

PLC Basics

What is a PLC?
You may have heard of Programmable Logic Controllers (PLC), but still find yourself wondering, how to get started learning PLC Basics? With the the different types of PLC products and brands available, it is easy to get lost before even getting started learning PLC Basics. Today, the most common PLC products are manufactured by the following companies:

Allen Bradley
GE Fanuc
Klockner Moeller
Mitsubishi
Omron
Schneider Electric
Siemens

As you can see, with the various choices in manufacturers all claiming different technology claims, it is easy to wonder where to start
So what exactly is a PLC?
A PLC is a device that gathers information (inputs) and uses a preconfigured program inside (logic) to make decisions and generate desired results (outputs).
How much training is required to learn PLC Basics?
Even PLC experts started their journey to a wealth of PLC knowledge with a few first steps. The easiest way to start learning about PLCs is to begin by building a solid foundation that all other knowledge will be built upon. With that in mind, the following books are non-brand specific and will build that solid foundation.

What are some good uses for a PLC?
In case you're looking for a reason to learn about PLCs, here are some great uses for them:

Manufacturing - Escalators, lifting operations and complete plant control
Food Industry - Filling machines, Batch and Process control
Textile Industry - Washing machine controls
Plastics Industry - Extruder, Injection molding control systems
Agriculture - watering systems
Amusement Parks - Roller coaster ride and effects systems

This is just a sampling of how a PLC can help control a process or operation. The 10 billion dollar PLC market continues to grow annually as the technology improves and expands into new applications.

How to find PLC training?

Many individuals struggle to find PLC Training specific enough to address their needs. The trouble is, Classroom style PLC training is expensive and generic. It’s almost impossible to learn PLC programming without traveling to a class or searching all over the internet. Both of these methods waste countless hours searching though unorganized or non pertinent information. Before investing large amounts of time or money on PLC training, the following resources are a great way to learn the specific pertinent information you’re looking for.

Programmable Logic Controllers - Frank D. Petruzella

Programmable Logic Controllers - James A. Rehg

Introduction to Programmable Logic Controllers - Gary Dunning

As you can see, there are many different options to train yourself on PLC Basics. Building the solid foundation is a key first step to ensuring success down the road.

How much PLC training is required?

Because each person’s definition of PLC training is different, there is no single answer. This is why PLC classroom trainings are not the most effective way to learn. Putting many students with different goals in the same classroom results in a lot of time wasted listening to facts that don’t matter.

How to maximize the effectiveness of PLC training?

Understanding what needs to be learned is a key first step. Individuals who have had the most success learning about PLC training apply the following principles.
1. Make a list of specific learning objectives.
2. Search out those items in books or using other resources.
Once a solid foundation has been built, it is easy to apply just in time learning principles by contacting training companies and asking about how their training would address remaining learning objectives left over from the initial list.
PLC training is the start to an incredible journey. Initial research evaluating the specific learning topics saves time and thousands of dollars worth of formal training. Intuition has brought you here and by continuing to invest in yourself, the technology of the future becomes easier to grasp.

PLC Programming

How to Learn PLC Programming?

You may be familiar various forms of Programmable Logic Controllers (PLC), but still find yourself wondering, how to get started PLC Programming. Don't worry; it's a completely legitimate question, especially because of the different languages available. You may commonly find PLC programming using the following methods:

Function Blocks
Ladder Logic
Sequential Function Charts
Structured Text

As you can see, with the various choices in PLC programming languages available, it is easy to wonder where to start.

Where to use PLC Programming Languages?

In most cases, each PLC programming language has a unique purpose. The uses will vary slightly from person to person but here are the general strengths of each PLC programming language:

Ladder Logic – Most common, general purpose and easy to troubleshoot
Function Blocks – Process Applications
Sequential Function Charts – Events occurring over and over in the same order
Structured Text –Text based programming option is preferred

This is just a sampling of the different types PLC programming languages available. Each language has benefits and drawbacks that vary based upon application.

How Exactly to Learn PLC Programming?

After identifying the PLC programming language for a specific application, learning objectives become easier to focus on. The resources below are some great places to get started.

The Hands on Approach to PLC Programming

If you’re the type of person who learns best by doing, a simulator with instruction manual may be a great place to start. Simulators also come in handy down the road for testing out logic when you cannot take down a machine to try something out.