Do you know how to scale your analog input? Or wire your analog output?
Many people struggle with analog signals in PLC programming. The wiring and how to use an analog input or output in your PLC program can be tricky. Most often you will see digital example PLC programs and in my Structured Text Tutorial most of the examples are digital programs.
I’m writing this article because many of you wanted to learn how to use analog signals in PLC programming. Analog signals are used widely in PLC programs but also often used in a SCADA system. So how do you connect that 4-20mA analog transmitter to your PLC and use it in your PLC program? How do you scale an analog [...]
One of the official and widely used PLC programming languages is Function Block Diagram (FBD). It is a simple and graphical way to program any functions together in a PLC program. Function Block Diagram is easy to learn and provides a lot of possibilities.
Do you also struggle reading your own and others huge ladder diagrams?
The truth is, that even though ladder diagram (LD) is an easy programming language for beginners, it can be very hard to read and understand. That’s why Structured Text is a better PLC programming language, and you can learn it in this tutorial.
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.
Now, that we know what hardware is inside the PLC, the next step will be to take a look at the software inside the PLC and how it runs. Every PLC has a scan time and a scan cycle. This is how the PLC and the software inside the PLC works. The scan cycle is the cycle of which the PLC gathers the inputs, runs your PLC program and then updates the outputs. This will take some amount of time often measured in milliseconds or ms. The amount of time it takes for the PLC to make one scan cycle is called the scan time of the PLC.