The History and Evolution of PLCs

The Programmable Logic Controller (PLC) has transformed industrial automation, replacing relay-based control systems and revolutionizing manufacturing, process control, and infrastructure management. But how did PLCs evolve into today’s powerful, smart automation tools?

The journey of PLCs dates back to the 1960s, when industries needed more efficient and flexible control systems. From basic logic controllers to AI-powered smart PLCs, their evolution has been driven by technological advancements and industrial demands.

Let’s explore how PLCs originated, evolved, and continue to shape the future of industrial automation.

The Origin of PLCs: The 1960s – A New Era in Automation

Before PLCs, industrial control systems relied on hardwired relays, timers, and mechanical switches. These systems had significant limitations:

• Time-consuming setup and modifications
• High maintenance costs
• Frequent wiring errors
• Limited scalability

In the mid-1960s, the automotive industry (particularly General Motors) needed a faster, more flexible solution for controlling automated assembly lines. The goal was to replace complex relay-based logic with a programmable system.

The First PLC: 1968 – Modicon 084

In 1968, Dick Morley, known as the "Father of PLCs," developed the first-ever PLC: Modicon 084. The name "Modicon" stood for Modular Digital Controller, highlighting its modular and programmable nature.

Key Features of the First PLC (Modicon 084):

• Eliminated relay logic wiring
• Used digital programming (instead of physical relays)
• Offered reprogrammability via software-based control logic
• Enabled faster troubleshooting and modifications

This breakthrough marked the beginning of modern industrial automation, and soon, PLC adoption spread across various industries.

The 1970s: Expansion and Standardization

During the 1970s, PLCs became more reliable and widely adopted across industries like manufacturing, oil and gas, power plants, and water treatment.

Major advancements in the 1970s:

• Introduction of Ladder Logic Programming – A language resembling relay circuits
• Memory & Processing Improvements – Supporting more complex control logic
• Industry Standardization – Emergence of standards like IEC 61131

Companies like Siemens, Allen-Bradley, Mitsubishi, and Omron began producing more advanced modular PLCs.

The 1980s: PLCs Become Smarter and More Powerful

The 1980s brought major technological breakthroughs, evolving PLCs into high-performance systems.

Key developments in the 1980s:

• Microprocessor Integration – Enabling faster, more complex automation tasks
• Modular Expansion – Scalable I/O module additions
• Networking Capabilities – Protocols like Modbus and Profibus
• Better Memory & Storage – Introduction of RAM and EEPROM

By the late 1980s, PLCs were replacing traditional relay systems across industries.

The 1990s: The Rise of Software-Based Automation

The 1990s saw software enhancements that made PLCs easier to program, diagnose, and troubleshoot.

Notable PLC advancements in the 1990s:

• Graphical Programming – With Function Block Diagram (FBD) and Sequential Function Chart (SFC)
• SCADA & HMI Integration – Better process monitoring and control
• Remote Access – Engineers could troubleshoot and update PLCs remotely
• Widespread Industry Adoption – Became dominant in control systems

The 2000s: Internet and Advanced Connectivity

The internet era brought smarter and more connected PLCs.

Key advancements in the 2000s:

• Ethernet/IP, Profinet, and IIoT protocol adoption
• Wireless PLCs for real-time remote control
• Faster processors for efficiency
• Enhanced cybersecurity with encryption layers

These advancements laid the foundation for Industry 4.0 and smart automation.

The 2010s & Beyond: Smart PLCs, AI, and Industry 4.0

Today, PLCs are smarter and integrated with emerging technologies.

Recent Trends in PLCs:

• IIoT Integration – Cloud-connected for predictive analytics
• Edge Computing – Local data processing for faster response
• AI & Machine Learning – For predictive maintenance and optimization
• Cybersecurity – Built-in protections against modern threats

The future of PLCs lies in self-learning automation systems that combine AI, ML, and IoT to enable real-time optimization and intelligent control.

Conclusion

The evolution of PLCs from basic relay replacements to AI-powered smart controllers highlights their vital role in modern industry.

Today’s PLCs are faster, smarter, and more connected than ever before—driving the future of automation, Industry 4.0, and smart manufacturing.

As industries continue to evolve, PLCs will remain central to intelligent automation—ensuring efficiency, safety, and productivity.