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What are the main differences between Industrial PC’s and PLC’s? Why would you choose one over the other? Read on to explore 5 main differences that you need to know about when making this critical decision. 

With the advancement of technology in recent years, the performance and reliability of industrial computers has vastly improved. Additionally, the prices have reduced and they are now used widely in many control and automation processes. Industrial computers are highly reliable, respond in real-time and easily expandable. These computers can provide both digital and analogue connections and are built to last in harsh industrial environments. 

PLC

Photo courtesy of CyberVisuell

The PLC or Programmable Logic Controller is an industrial control device that was invented in the 1970s. This microprocessor controlled device makes use of relay-style logic control that manages counting, timing, pulse control, analogue quantities, mathematical calculations, and other important control tasks. PLCs can thus be considered as specialized computers for industrial control.  

Here are the key differences between industrial PC’s and PLC’s: 

1. The Structure:

Both PLCs and Industrial Computers consist of a Central Processing Unit (CPU) along with input and output units and memory. However, in the PLC, the processor is typically lower power and designed for executing repetitive logic style tasks, with a dedicated calculation unit. Software is typically built into the PLC with dedicated, proprietary operating system and control software. On the other hand Industrial PC’s are based on the evolution of Personal Computers, with a very powerful general-purpose CPU adhering to compatibility standards and running desktop-style operating systems. This means that the PC needs to have a suitable operating system installed (e.g. Windows or Linux), which then needs to be configured properly, before installing the control software.

2. Cost-Effectiveness:

Industrial computer devices are known for their high performance, wide applications, modularization, integration and flexibility. However, this comes at a much higher price point. By comparison, PLC’s are much more cost-effective as they are purpose designed and do not need to run third party software. With the integrated nature of the PLC, system integrators can meet all their requirements with a low cost control device. 

3. Peripherals and I/O:

When it comes to peripheral configuration, Industrial computers offer more flexibility than Programmable Logic Controllers, but require external add-ons for wiring up sensors and control devices. The available network interfaces (wired and wireless), displays, printers, local and remote I/O modules, human interface devices, and other components of an industrial computer are much richer. In such computers, even peripherals by different manufacturers can be brought together and used with corresponding driver software. However industrial PC’s generaly do not have built in inputs for wiring up sensors, solenoids, relays etc – it is necessary to add plug-in cards or USB I/O modules to provide such interfaces. With PLC’s, there are normally several sensor inputs and control outputs built into the PLC, with more available via expansion modules. The rage of other peripherals such as networks, displays, printers etc, is quite limited, and equipment from different manufacturers often cannot be attached. 

RENU Electronics PLC's and HMI touch screens

Photo courtesy of RENU Electronics

4. Human-Computer Interfaces:Human-computer interface devices such as touch displays are used to allow humans to monitor and control PLC systems. These devices are used for data display, animation, parameter setting, and other automation control processes, and help in simplifying the PLC program. When using industrial PC’s, there is more flexibility in the range of human-computer interfaces that can be used. In addition to the commonly used touch screens, you can also attach large screen displays, separate keyboards and pointing devices, and even set up remote access via the internet. Modern day PLC’s are beginning to offer similar capabilities but they are generally more limited in terms of compatibility and functionality.

5. Programming tools:Advanced programming languages like C, C#, Python can be used in industrial computers to make the application writing process intuitive and powerful. However, developing a control application in this kind of language can take a lot of engineering time and effort. To learn the language and write an application, the programmer needs to have a a deep knowledge about both good software design and how to interface with the hardware. The other option is to use a ready made SCADA package on the industrial PC, which can be configured and programmed at a very high level. This can be much quicker and easier than developing one’s own software. By comparison, PLCs are supplied with built-in control software, which is programmed using intuitive ladder diagrams and well defined languages such as Structured Text. This doesn’t take much time for software or hardware development. This also means PLCs are easy to maintain and modify by other personnel if the requirements change over time.

ESIS specializes in PLC’s and Industrial PC’s, and is the leading supplier of industrial electronic equipment in the Australian market since 1971. Choose from our wide range of products to best suit your requirements.

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