PLCs can range from small modular devices with tens of inputs and outputs (I/O), in a housing integral with the processor, to large rack-mounted modular devices with a count of thousands of I/O, and which are often networked to other PLC and SCADA systems.
It is needed to automate machines in the industry so that human efforts can be reduced thus minimizing the human errors that might occur in the process. Consider a situation where a human handling a system missed to switched the motor on. Imagine the delay it might cause in the operation to begin. The simple solution to solve this is by automating the motor using PLC. So the basic and most important use of PLC is in the automation of machines.
There are many PLC manufacturers, for example Siemens, Beckhoff, ABB, Allen Bradley etc. We shall focus on mainly Beckhoff and Siemens PLC in this site.
There are many ways to program PLC. 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.