First released in 1993, the International Electrotechnical Commission’s IEC 61131 programming standard remains a key element in the programmable logic controllers (PLCs) used in a variety of industries across the globe. The IEC 61131 standard is especially useful in Open Architecture control systems. These systems use standard programming languages to operate efficiently, accurately, and cost-effectively.

This article reviews what Open Architecture control systems are, IEC 61131 development, its programming languages, as well as their benefits.

Open Architecture Control Systems

Open Architecture control systems make adding and upgrading software components easier. Therefore allowing third-party vendors to improve their current systems. Upgrading to an Open Architecture control system offers owners and operators several benefits. Some of these include lower costs than switching to a proprietary system, minimal inventories of spare parts, and straightforward maintenance and service requirements. Other benefits include a more mature overall design than original systems, lower support costs due to their self-servicing capabilities, and higher standards for software and functionality than original systems. Also, because Open Architecture control systems use the same controller as other control systems, they also provide more flexibility for owners.

The Development of IEC 61131 and Its Programming Languages

In developing the 61131 standard, the IEC identified five programming languages as the most common for a variety of programmable controllers. These languages enjoy widespread adoption across industries, and more diverse methods for implementing various control functions. The IEC 61131’s five programming languages are Ladder Diagram, Instruction List, Function Block Diagram, Structured Text, and Sequential Function Chart. Each language has advantages and disadvantages depending on a control engineer’s desired application.

For example, Ladder Diagram has the advantages of universal language acceptance and increased ease of changing code. While Instruction List and Structured Text offer European acceptance and increased PLC ease of execution. Structured Text is also much easier for controls engineers to learn and use. Also, it allows complex mathematical operations to be implemented with ease. Sequential Function Chart makes final user maintenance simpler and is especially useful in applications that contain repeating processes. It is also effective in processes with interlocks and concurrent operations.

The Benefits of the IEC 61131 Standard in Open Architecture Control Systems

PLCs that use one of the IEC’s programming languages are beneficial in several ways. Users and vendors can expect less waste of human resources thanks to decreased training, debugging, and system maintenance times. The software will also experience fewer errors and increased performance. Controllers from different locations, projects, or companies can be used together harmoniously. And thanks to IEC 61131, various programming techniques are now applicable in a wider range of environments. It also provides more connectivity, which helps protect investments.

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