PLCs have a long and storied history, with Allen-Bradley itself coining the term “programmable logic controller” in 1971 when it introduced its version of what was then called the “programmable controller.” For anyone who cut their teeth on ladder logic can testify, PLCs at the time were an elegantly simple solution to an age-old problem: making control systems reconfigurable without having to manually rewire or reconnect the hardware. The modern programmable logic controller (PLC) is still today very important part of factory, industrial, and manufacturing automation. It’s this flexibility, combined with more powerful processing, programming simplicity, and ruggedness that keep PLCs at the forefront of industrial control platforms. Over time the decision between PLC and PC/embedded-computer-based systems has become more to do with installed base, designer familiarity and legacy perceptions, than real technological or ruggedness differentiators. As we move toward the Internet of Things (IoT) and Industry 4.0 or 4.2, the choice may sway back and forth again for new factories and systems, but odds are the two architectures will coexist for many years to come.
Teardown: Ruggedness and flexibility keep PLCs strong in industrial article shows a tear down a popular PLC, the Allen-Bradley Micro850. The article explore some of the choices made in its design to shed light on core I/O isolation options along with some of the elements that go into a well-known PLC design.