The Development Process of Programmable Controllers: 1968 to 2026
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The Development Process of Programmable Controllers: 1968 to 2026
As PLC professionals who have spent two decades sourcing, programming, and supporting programmable controllers across
Detail
systems, we have watched this technology evolve from cabinet-filling relays to today’s software-defined controllers. This Engineering Note revisits the development process of programmable controllers and brings the story current to mid-2026, with the soft-PLC, OPC UA over TSN, and on-device AI milestones that have reshaped the field since 2024.
The first programmable controller, the Modicon 084, shipped in 1968 as a solid-state relay replacement for General Motors.
Through the 1970s and 1980s, microprocessors turned PLCs into compact, affordable units with PID and analog I/O.
The 1990s brought graphical programming (ladder logic, function blocks) and the first fieldbus networks.
By the 2010s, PACs and PLCs converged, with Industrial Ethernet (Profinet, EtherNet/IP) becoming the default.
Since 2024, IEC 61499, soft-PLC runtimes, OPC UA over TSN, and on-device AI inference have defined the 2026 control architecture.
In 2026, the PLC is no longer a dedicated black box on a DIN rail; it is a software workload that runs wherever it makes sense. Sourcing spans CPU, runtime, and edge cloud.
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