The programmable logic controller (PLC) was invented in the 1970s, in response to the needs of automotive manufacturers for real-time relay ladder logic programming that could be easily understood and accomplished by the average electrician. Also developed in the 1970s, distributed control systems (DCSs) were initially minicomputers, but moved quickly to specialized workstations and networked Intel-based PCs.

For several years, PLC applications remained focused around discrete automation markets, while DCSs expanded primarily in process control systems. The rapid growth of the PC in the 1980s soon led to extensive industrial use. PCs became the easiest way to connect DCSs, PLCs and remote I/O into the rapidly expanding hierarchy of factory and plant networks and the Internet.

The standard PC was not used widely in industrial applications for three primary reasons: The operating systems were not suitable for control; components such as disk drives and fans were prone to failure in industrial environments; and factory and plant engineers and technicians had completely different skills from IT personnel.

Because of higher-level capabilities, low-cost communications and networking, and driven by an increasing rate of technological advancements in hardware and software, industrialized PCs started to replace programmable controllers in many industrial applications. But the market still remains fragmented among many different suppliers.

The increasing use of the PC in industrial environments led to the definition of a new class of industrial computer: the programmable automation controller (PAC). This type of product employs open industry standards, combining the functionality of a PLC and a PC. The PAC acronym is now being used by both traditional PLC vendors and industrial control companies to describe their industrial control platforms.

Today, the use of PACs continues a shift in emphasis toward communication standards and software integration, with less emphasis on the hardware and more focus on total system performance.

Post-PC Era

The shift has begun to replace traditional PC hardware with "thin client" products - diskless, fan-less, with no hard drives, no storage space, no programs to upload or update, sometimes not even a resident operating system. This delivers vastly improved productivity and drastically reduces the total cost of ownership.

What we are seeing is not the death of the PC, but the gradual erosion of its importance - a shift in focus away from traditional systems and onto newer devices.

PCs are giving way to tethered (powered) and untethered thin clients and post-PC devices like smartphones and tablets. Raw horsepower is giving way to low power consumption. Processors are now so powerful that even inexpensive gadgets can handle most tasks.

Rarely do people consider smart processing and gigahertz anymore - power and performance have been sidelined. Local storage requirements are falling as more and more data is being pushed into the cloud, which also offers a convenient solution to syncing data across multiple devices.

The prolific and perennial inventor Dick Morley, acknowledged "father of the PLC," makes these projections: "More and more computer chips will be used in industrial monitoring; there will be less and less system complexity. To some extent, controls people consider computers and operating systems irrelevant. It's the connectivity that's critical, not the content."

A major inflection point is quickly approaching for industrial automation. It is simply a matter of time before significant new growth occurs. My own view is that it's happening right now. Big changes will be evident in less than a decade.