The blurring lines between Programmable Logic Controllers and traditional PCs

Programmable logic controllers are one of the essentials of any modern factory. However, nowadays we are seeing a situation where traditional PCs are being designed to fulfil a lot of tasks that would be traditionally PLC’s purview and a lot of PLC’s which are taking forms resembling that of a traditional PCs. Let us explore this situation where the two are encroaching on each other’s territory and the differences that remain.

The history of programmable logic controllers

The industrial era has undoubtedly changed humanity. The advent of mechanised manufacturing increased productivity exponentially. However, the mechanised manufacturing involved many complex steps. A lot of them had to be managed manually by a machine operator who triggered the right functions according to what he observed or according to a set of sequences.

Some advanced machines used some clever mechanical contraptions that could physically trigger the right actions based on parameters such as fluid level or steam pressure. However, this was highly dependent on physical conditions and not very reliable or efficient. It was also very crude and could not be used for precise control.

The advent of electrical switches and relays moved things ahead. A lot of the industrial machines were operated by machines, which could be controlled by electric switches. A systematic arrangement of these in the form of relays in combination with physical triggers could be used to control a lot of industrial processes.

These switches were usually arranged in boxes, called switchboxes. These boxes started getting absurdly complicated as the complexity of the system being controlled became more complex. Hence, GM issued a requirement for a control system to replace it in the late 1960’s, in response to which the Modicom 084, the first PLC was developed. By mid-1970’s, the PLCs were using contemporary microprocessors. By the turn of the century, they had quite advanced functionalities and quite common in advanced factories.

The history of PCs

Personal computer had quite a different beginning. It began as a mostly information processing system but was not initially designed to actually do anything with the information. The early personal computers of the 1980’s were made to bring the information processing power of massive mainframes to the masses. What began as artillery table calculating and code-breaking machines in the second world war evolved to general purpose machines which could be used for playing games or maintaining business accounts.

The development of PCs has generally continued as an information-centric device. But recently, there has been the development of a lot of hardware that allows a PC to directly control physical devices. A PC can control industrial machines via hardware interfaces that connect usually via serial or, more recently, USB interfaces.

The current scenario and the future

Programmable logic controllers were purpose-built to fulfil industrial control role, but PCs emerged as a general purpose device. This nature has allowed them to adapt to control machines as well. On the other hand, many PLCs have PC like functions such as networking and graphical interfaces with applications. With the advent of smaller and cheaper computers such as Raspberry Pi and more expensive high-end industrial control computers, newer devices seem like a hybrid device that can be whatever you want to be.

Conclusion

Even though newer machines are controlled by such devices, traditional programmable logic controller still remain popular since their specialisation and momentum in the industry. There are many companies which use PLCs with several decades of remaining life, which is uncommon for a PC. Such systems can be serviced by reputed PLC service companies such as Ally-controls.com.

Ally Controls LLC

www.ally-controls.com