![]() As the world moved into the twenty-first century, these advancements in PLC technology would help pave the way for manufacturers to implement a new era of internet connectivity, big data, and even forms of artificial intelligence on the factory floor. However, with continued development and growing demand for machine monitoring, HMIs gained the ability to translate the machine data being recorded by PLCs and display it in the form of system status, alarms, cycle times, reports, production counts, and more.īy the end of the 1990s, PLCs were becoming smaller, faster, more powerful, and equipped with significantly more memory. Initially, HMIs were merely a digital replacement for physical pushbuttons and were considered too expensive for applications that had less than 20 pushbuttons. This idea led to the development of the human-machine interface (HMI). In addition, the terminals would allow operators to quickly see what was wrong with their machines preventing them from having to spend hours troubleshooting. In the 1990s, manufacturers began requesting for machinery to include interactive terminals that allowed them to monitor their PLC software. ![]() The IEC also established five PLC compliant programming languages, consisting of LD function block diagrams (FBD), sequential function chart (SFC), structured text (ST), and IL. More specifically, the standard ensured functions and function blocks looked the same and had the same defined inputs and outputs, making it easier for engineers or maintenance personnel to understand the program. The IEC brings consistency to PLC software programs by defining various standards for data types, naming conventions, program flow, and other programming elements. The 1980s also saw the introduction of the IEC 61131-3 Standard for Programmable Controllers, which is the standard all PLC software is held against. ![]() This led PLC manufacturers to develop and market their own competing programming packages, as well as purchase many of the third-party software companies. These third-party software packages also offered vastly improved documentation and reporting capabilities over the OEM programming devices. Third-party software packages that worked with multiple PLC hardware platforms came available in the 1980s to alleviate the high cost of early programming devices. The programming devices were also only compatible with a single manufacturer’s controllers, further reducing their utility. Unfortunately, these programming devices were prohibitively expensive, often costing more than the PLC they were designed to program. These devices enabled PLCs to be digitally programmed with graphical representations for normally open and closed relay contacts, pushbuttons, switches, relay coils, motor starters, valves, timers, and more. ![]() With inexpensive microprocessors becoming available in the late 1970s, PLC manufacturers began developing graphical programming devices. In addition, the PLC was equipped with enough memory to retain loaded programs in the event of power outages and was also designed to operate in industrial environments where dirt, moisture, electromagnetism, and vibration were often present. The emergence of the first PLC in 1968 meant large banks of relays could be replaced by a single device that was easier to maintain and could be programmed with the already accepted relay ladder logic. Furthermore, implementing changes posed another set of challenges as they often required reconfiguring the entire system. If just one relay malfunctioned, the entire system would stop working, and troubleshooting could, at times, take hours to complete. Additionally, the relays had to be wired in a specific order for the machine to operate properly. Most of these challenges stemmed from the need to use several relays to control just one machine, which took up large amounts of space. At the time, using relays and timers for applications that are now handled by PLCs posed numerous challenges. The first programmable logic controllers were developed as a solution to replace large banks of hardwired relays and timers. Since then, PLCs have evolved to be smaller, faster, and more powerful to keep up with the increasing demands and sophistication of modern manufacturing. Developed in the 1960s, PLCs started out the size of suitcases and required logic programs to be drawn out on a drafting board before being loaded onto the device with a numeric keypad. Programmable logic controllers (PLCs) have become an essential device for automating manufacturing processes. ![]()
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