In the world of food blending and packaging where I make my mark on the world, it is easy to forget that not every control system has a programmable logic controller (PLC) as the heartbeat of the control system. PLCs were designed specifically to control machines and processes in harsh environments where extremes in temperature and humidity would render its counterpart, the personal computer (PC) inoperable.
PCs, on the other hand, are well-suited for an office or a climate-controlled room. PLCs would tend to be programmed using pneumonic or ladder logic whereas a PC would be programmed using a text-based programming language. PCs, therefore, were ideally suited for process control where they could be isolated from the environment in which the process operates. Isolating the control system from the environment tended to be costly and require a great deal of extra effort to make it work successfully.
Traditionally, a PC would sit on a table in an office or a laboratory with a monitor, keyboard and mouse plugged in to the base unit to provide the interface with the control system. Interface cards would be added to the PC to reach the field devices. These could be industrial network protocol expansion cards for the likes of DeviceNet, ControlNet, Profinet or Ethernet I/P but could also be specialty input or output cards, as well.
One of the main advantages of that PC is the powerful processor and significant onboard memory over a traditional PLC. The process control can be developed using high-level programming languages and can feature custom graphical user interfaces (GUIs) that just are not normally available at the PLC level of hardware.
A PC can directly interact with a server in a number of ways that a PLC cannot. In fact, a PC can reside on a server-based operating system. For this reason, PCs are often used as high-end supervisory control and data acquisition (SCADA) systems.
The need to bridge the gap between PLCs and PCs led to the development of the industrial programmable controller (IPC). With the introduction of the IPC, the computer and interface—screen—were relocated back out to the floor, right at the heart of the process.
The core benefits of an IPC, located near the process being controlled, start with using the same technology as a desktop computer. Units are full-strength industrial computers, able to withstand harsh environments. The base unit is fanless, meaning that the computer is in a sealed package with cooling fins on the outside to manage the internal operating temperature. Most come with either Windows 11 or Windows 10 or Linux operating systems and, as such, can run any software package available to those platforms.
Many hardware suppliers offer IPCs, and they can come in a variety of configurations. Suppliers offer versions where the base computer is standalone and peripherals are plugged into it, while other versions can be panel-mounted where the PC is integrated with a touchscreen for the graphical interface and processor in a complete package.
Industrial PCs have their own commercial operating systems and, as mentioned previously, can run any software platform designed for that operating system. Programs can be written in Visual Basic, C++, Python or any other programming platform, providing great flexibility in the finished design. Many hardware suppliers provide developer libraries to aid in integrating peripheral devices into the control design.
Unlike a PLC or programmable automation controller (PAC), an IPC can run multiple software applications at the same time. The huge advantage here, for example, is running a customized main control algorithm and being able to open up instances of other software products at the same time. Imagine a part-checking solution where the operator interface is a customized graphical interface that opens a pop-up window executing the vendor-supplied software for the vision system.
IPCs are the ideal platform for running high-end SCADA packages that take advantage of huge processing power and large static memory in the IPC to provide a slick, fast interface to the process.
It would be remiss to extol the virtues of an industrial PC without mentioning a potential pitfalls of using a IPC in a controls solution versus a PLC or PAC. This has to do with the basic design of an industrial PC. At its core is a computer. It is a motherboard with a processor, graphics card, peripheral boards and an operating system. Technology moves on in great leaps, and operating systems have to follow or become obsolete. When we first purchase a PC, we are usually getting the latest and greatest technology with the best operating system available today. We install software on that PC that works with that operating system.
A PLC is based on a dedicated operating system and all of the add-on components are designed back on that dedicated system. For this reason, it is not unusual to have PLCs still operating in a production environment as many as 30-40 years after they were first installed.
To take advantage of the broader design possibilities, many hardware manufacturers of products that will sit on a plant floor or in a processing facility will choose to base their projects on an industrial PC. At first, it makes sense. The development environment is much more powerful, the graphics are very eye-pleasing and the base software product can be designed and tested on a PC or laptop and then transferred into the finished hardware product. Examples of these types of products are check weighers and marking equipment but can also include operator stations.
There is no argument that the advent of industrial PCs has enhanced the development of large-scale SCADA systems and opened up possibilities when it comes to control design by allowing for IT programming languages to be used in the OT world. As long as we are careful about where we choose to use this technology, the advantages far outweigh the risks.
