The most common types of control architectures used this day include programmable logic controllers known as PLC and Programmable Automation Controller known as PAC. If you are not sure about which one to choose, then you can use the following factors to make an informed decision.

Processing Speed

One of the most critical factors in making the right decision includes computation or processing speed. On that front, PLCs have a traditional edge. They are designed specifically for specific control tasks with the processor handling dedicated motion tasks.
PACs, on the other hand, may be involved in doing several tasks simultaneously along with motion control that can cause competitiveness between various computing resources.
However, the advanced systems these days are equipped with fast processors that eliminate this issue. In fact, they have a higher processing speed that makes them more reliable for complex functions that a PLC may not be able to carry out with efficiency.


Another critical issue impacting speed is memory. Needless to say, modern-day PCs have greater capacity and thus have a higher ability to store data. However, PLC is specifically designed to handle large amounts of Input/Output, therefore capable of processing data more efficiently.

System stability

Another critical issue faced by PCs is system stability. The operating systems are often vulnerable to complete breakdown, also known as the Blue Screen of Death. However, the advanced PC operating systems these days are more stable, circumventing this concern altogether.
PLCs, on the other hand, are scalable and also come equipped with the power of a programmable automation controller (PAC) in a cost-effective controller.


Easy user interface

Users these days are more familiar with PC OS, making it simpler to use and troubleshoot. Additionally, the Graphical User Interface (GUI) is similar to the one that makes it easier to work on the system. PLC, however, has a complicated interface.
PCs also have an added advantage of sophisticated hardware that gets updated on a regular basis, making it more practical to update as compared to PLC. Therefore, it is safe to assume that a PC-based PAC system is much simpler to use, maintain, and configure due to ease of use and understanding.


PLCs are designed to handle a certain number of tasks such as monitoring, I/O processing etc. However, they are incapable of doing other tasks such as upgrading and downloading system updates that a PC-based controller can handle easily.


With rising competition in the market, it is possible to get faster processors at a cheaper cost. These processors are usable in both PLCs and PACs. So, in a way, there is not much price difference when it comes to the systems. However, there are some other factors such as I/O, memory, and expansion modules that can influence the price.
In the end, it is safe to say that a large number of engineers always look towards PLCs as their preferred solution. However, with the increasing dependence on data storage and information exchange with IoT and automation, PAC based controllers may appear to be a more attractive choice.
Modern-day PLC and PACs have similar features, and both can be used interchangeably in many applications. However, the final selection gets determined based on multiple factors for different applications, company environment, future expansion plans, vendor relations, and previous experience with automation platforms.
Therefore, there is usually no right or wrong answer to the design problem. You only need to keep the essential aspects of engineering in mind when making a decision. Or, you can approach a certified professional for the same!


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