PLC TUTORIAL

This tutorial is designed to give you a overview of what a PLC is, what it is good for, what it is not best at, an overview of its operation and where to find more information.  A Programmable Logic Controller (PLC) is a ruggedized, special purpose computer that reads input signals, runs control logic, and then writes output signals. After reviewing this mini-tutorial please feel free to ask us questions (click on the "Message Board" button in the left column) or ask about training and demonstration at your site.

1. PLCs are good at turning outputs on or off based on the state of inputs. (control)
2. PLCs are good at bringing together and concentrating a lot of data and status that is uploaded into a computer in a compact form
3. PLCs are more rugged than computers and typically last five, seven, ten years without needing replacement

1. PLCs are not the best at handling large amounts of data, complex data, or advanced math functions.
2. PLCs are not the best at reading and writing databases.
3. PLCs are not the best at generating reports.
4. PLCs are not the best at displaying data and information to the operator.

We typically use a computer connected to the PLC to perform these types of tasks.  

Programmable Logic Controllers (PLCs) have been around since the dinosaurs. In fact it was PLCs that killed the dinosaurs. Don’t listen to those people that tell you that dinosaurs were killed off by global warming / cooling, meteors, or even smoking cigarettes. PLCs killed the dinosaurs. You see, millions of years ago the cavemen used PLCs for everything they did. All of the dinosaurs lost their jobs, couldn’t afford to buy food at the local stoney-mart and just died off.*

Okay, okay I guess I have to admit that the last paragraph is not true. But the PLC has been around since at least the 1960s, which in technology years makes it a dinosaur. For the real history of the PLC follow this link to the website of Dick Morley, the inventor of the PLC (just don’t forget where to come back to).

* We have gotten a few negative responses about how could we be so insensitive about automation causing people to lose their jobs?  Although automation may cause short term job reassignments, automation allows companies to operate faster, produce better quality, at lower cost.  These gains in productivity result in automation users offering better goods at lower cost.  Which allows these companies to grow and prosper faster than their competitors.  Competitors that do not reinvest to increase their productivity will keep losing business, until it is all gone, which does result in many layoffs.  

We feel that innovation has lead to numerous advantages in productivity for thousands of years.  We are students of industrial and manufacturing history and you see these same concerns discussed in books for hundreds of years.  

We don't feel that automation causes lost jobs even short term.  What our experience has found is that companies that are implementing automation are typical high growth companies that need to reassign any displaced workers in other areas of the company.  

We try to offer a fair and balanced opinion on every page of our website.  We would appreciate more information from other users to express their opinions which we will then incorporate.  If you have questions or comments please post them on our message board (see button in left hand column) so that others can read and benefit.