Open PLCs and Linux-Based Controllers: Pros and Cons

Industrial control is evolving beyond proprietary rack PLCs. A new wave of open, Linux-based controllers — like PLCnext, Codesys Control, and OpenPLC — brings flexibility, openness, and edge-AI integration to automation engineers. But openness comes with trade-offs.

The Promise of Open PLCs

• Freedom of architecture: Run IEC 61131-3 code alongside Python or C++.
• Integration power: Easy connection to MQTT, REST, and OPC UA stacks.
• Hardware choice: Works on x86, ARM, and industrial PC platforms.

The Risks

• Hard-real-time limits: Linux scheduling adds micro-latency vs dedicated PLCs.
• Security footprint: Open OS requires patching, firewalls, and user control.
• Qualification effort: Regulatory approval may take longer in GMP or automotive environments.

Best-Fit Scenarios

• Hybrid systems where AI inference or data logging runs next to control logic.
• Retrofits where replacing I/O hardware isn’t viable.
• Applications needing web-based dashboards or APIs directly on the controller.

Case Example

A machine builder adopted a Codesys Linux runtime on IPC hardware. Integration with Python libraries for predictive maintenance saved two separate devices and cut latency by 40 ms.

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• Version Control for PLC Projects: Git without the Pain
• Lifecycle and Spares: Designing for 5-Year Support

Conclusion

Open PLCs aren’t for every factory, but they’re shaping the next decade of control. When combined with proper security and deterministic design, Linux-based control can deliver both flexibility and reliability.