Welcome to the second part of my ladder logic tutorial. In part 1 of the ladder logic tutorial I introduced you to the very basics of ladder logic and to some basic instructions.
In this second part of the tutorial I will teach you how to solve actual problems with ladder logic and how to use it to build PLC programs. At the same time you will be introduced to several other ladder logic instructions:Set / Reset CoilsSet or Reset PrioritySet / Reset Function BlocksSR Function BlockRS Function BlockBuilding Logic with Ladder LogicLogic Gates with PLC InstructionsOR and AND GatesNOT Logic GateInterlocking with Ladder LogicLadder Logic Exercise 1: InterlockingOne [...]
One of the best visual programming languages is a PLC programming language. It’s called ladder logic or ladder diagram (LD) and you can learn it very fast.
The smart thing about ladder logic is that it looks very similar to electrical relay circuits. So if you already know a little bit about relay control and electrical circuits, you can learn ladder logic even faster.
You may know the difference between normally open and normally closed contacts, but do you know where to use them? This article will teach you where to use normally open and where to use normally closed for inputs and in your PLC program. You will learn how to connect your PLC program with the physical PLC inputs.
Ladder logic symbols are the basic building blocks for ladder diagrams. Right here you will find all the ladder diagram symbols which are described in IEC 61131-3. The symbols are available for download in all formats and in a PDF-file.
I will start this article by making a confession:
When I develop a PLC program, I steal other people’s ladder logic.
I am stealing ladder logic examples for inspiration and solutions to my PLC programs.
From time to time you will be facing the same problem, when you do PLC programming with ladder logic. By looking at examples of ladder logic programs, you will be able to find a solution to your problem very fast. You may even find a smarter solution in the ladder logic examples than your own solution.
This is an introduction to PLC logic. You can use PLC logic to build PLC programs with simple electrical circuit diagrams. In this article, I will use combinatorial logic to build the functionality of a PLC program.
And to get as close as possible to real a PLC programming language like ladder logic, the PLC logic in this article will be contacts and relays in an electrical circuit.