How a PLC Programming works


A Programmable Logic Controller or a PLC is a computer or machine that comes with an operating system that is highly specific in managing processes in real-time. The PLC plays a very important role in the industry, especially in the processing, producing and manufacturing of different goods. So, if you are in a company with high tech facilities, then you might be working with engineers, who operates the PLC for monitoring and maintenance.

Not everybody understands how a PLC work. You have to be an expert in using the software for this type of environment as well as having a mastery of the language used in manipulating the system. For example, you must have a special training for RSLogix 5000, if this is the platform that the company you are working on is using. Without enough knowledge and skills of a PLC, then you would find it difficult to understand the operation of the system.

Even an engineer, who did not attend a specific training about PLCs won’t have sufficient skill to work for a PLC. That is why, if you have attended a training, then that would be your advantage to work as a PLC expert or operator. You will always have a lead over the other engineers because the PLC has a complicated process and learning it in a short time won’t be enough. Remember that this machine accepts various digital as well as analog inputs, executes a program and writes output.


The PLC Operation

Most PLC’s make use of a scan-cycle formatting, where it starts scanning the program from the top going to the bottom and then, from left going to the right. Every input that was scanned from the input card will be stored in the memory table.

After scanning the input, it will be logically executed using a program. And then, the input will also undergo a certain diagnosis, where it will be decided to perform a task and communicates this process or simply not to do anything.

When the process is completely diagnosed and executed, it will provide an output coming from the output memory table and it will be written through the output modules. Anyway, I have here a related site for you to check.


The PLC System


One of the components of a PLC is the rack, which holds every tangible part of the PLC. It may vary in size and shape, depending on the module that a company needs. This rack has a backplane, allowing communication between the cards and the Central Processing Unit or the CPU. The power supply is also needed to run the system. Most PLC’s works with a 120 VAC or a 24 VDC power source.

Another component is the CPU, which is actually the brain of the module and this one also varies, depending on how complex the system is. The CPU contains important parts, such as the memory chip, microprocessor and different circuits for monitoring, communicating and controlling logic. It also comes with various operating modes, such as programming, where accepting downloaded logics from computers are allowed. And then, the other mode is the run for executing programs and operating processes.

The last component is the Input and the Output for connecting the equipment and the PLC. Different I/O cards are also used for the logic and addresses in the program of the CPU. The I/O devices may be a digital or an analog device. Some of the examples of the Input devices are the push-buttons, the switches and the sensors. The Output may also be signals used in controlling and regulating positions.


The PLC Programming


There is a dedicated software used for programming a PLC. The most popular type of programming used is the ladder logic, which uses symbols in emulating the logic control to the real-time or real world. Lines are used to interconnect the symbols and these lines are also used in indicating the current flow. But, as the years passed, these symbols were enhanced and developed, providing a higher level of functionality. This sample at would be a good example of a basic ladder logic program for PLC’s.

If you are going to look at a complete ladder logic program, it will resemble a ladder formation, but it actually, it represents the electrical circuit of the system. This program, of course, is understood by the CPU of the PLC system. So, as an engineer, you really need to study this program and not only understanding the flow of electricity alone.


Who is required to do the PLC?

A PLC engineer may install, operate and maintain a PLC, if he has enough knowledge of the digital technology. Remember that the programming is not merely an understanding of the Boolean Logic and the Number Systems, but the ladder logic as well. With the PLC programming, you must have a fast response in developing the program. This is just like a mathematical problem that needs a specific solution. In such a way, you can come up with the desired result. You also need to know about the software that a company is using. Through this, you will be able to operate the system and perform various tasks.

Aside from that, you must also have knowledge on internal hardware of a computer. The other parts of the PLC machine are also necessary because you are in-charged with the maintenance. So, if there is something wrong with the other hardware or internal parts, then you must be able to determine what part needs to be checked or changed.

As a PLC engineer, you must know how to control the hardware because you need to operate the machine. You must be equipped with the right skills on how to control the input devices as well as the output devices. Other external devices, controls and relays may also be needed, depending on the complexity of the modules that the PLC needs to run or execute. Lastly, you must be able to validate the input as well as the output that the PLC is processing or executing.