When designing a modern industrial machine, engineers increasingly face a choice:
Should a traditional PLC handle machine control while a separate industrial PC or gateway manages data processing?
Or should an EdgePLC combine both functions on one platform?
There is no universal answer. The right choice depends on control requirements, computing workloads, reliability targets, and the complexity you are willing to manage.
Let's look at the engineering trade-offs.
In a traditional architecture, each device has a relatively clear responsibility.
PLC → Real-time control
Executes machine sequences and interlocks
Controls motors, valves, and actuators
Handles I/O and time-critical tasks
Industrial PC / Gateway → Data and applications
Collects and processes operating data
Connects to SCADA, MES, and cloud platforms
Runs dashboards, databases, analytics, or other edge applications
Why this architecture works
The control and computing workloads are distributed across separate devices. A heavy data-processing workload on the industrial PC is less likely to directly compete for CPU and memory resources with the PLC's control tasks.
It also provides a clearer boundary for troubleshooting and maintenance.
However, separation introduces its own costs:
More hardware, wiring, and power requirements
Additional communication links and protocol configuration
More software environments and update procedures
Additional integration and maintenance points
Communication between devices also requires careful design. Network delays, data synchronization, and communication failures must be considered, especially when data from the computing layer influences machine behavior.
An EdgePLC takes a different approach by bringing industrial control and computing capabilities together on one platform.
With a supported CODESYS configuration, engineers can develop IEC 61131-3 PLC applications while using the available hardware and software resources for industrial communication and edge applications.
A typical architecture might look like this:
Sensors / Drives / Modular I/O
↓
EdgePLC + CODESYS
→ PLC logic and machine control
→ Industrial communication
→ Local data acquisition and processing
→ Edge applications and system integration
↓
SCADA / MES / Cloud
Why consider this approach?
Less system complexity. Fewer physical devices can mean less wiring, fewer communication links, and a more compact control cabinet.
Simpler integration. Control and data processing can share a common platform, reducing the number of device-to-device interfaces that need to be configured and maintained.
More flexible application development. CODESYS provides a standardized PLC programming environment, while supported edge software can extend the system beyond conventional machine control.
Room for future functions. Depending on the selected model, a machine can incorporate additional local data processing, visualization, analytics, or AI applications without necessarily adding another computing device.
For OEMs building multiple machine variants, this can create opportunities to standardize hardware and software around a common platform.
But there is an important qualification: combining control and computing on one device does not automatically guarantee deterministic performance or complete fault isolation.
Those properties depend on the hardware architecture, real-time configuration, workload management, software design, and validation.
① Communication: How much data must move between devices?
If control and edge applications exchange substantial amounts of data, consolidating them may reduce external communication overhead.
If the system already has a well-designed industrial network and clearly defined interfaces, however, the benefit of consolidation may be limited.
② Maintenance: Is one platform easier to manage?
One controller can reduce the number of devices, firmware packages, and communication links to maintain.
On the other hand, a software update or configuration problem affecting a combined platform may impact more functions at once. Maintenance procedures and recovery plans remain essential.
③ Fault isolation: What happens when something fails?
Separate devices can provide a useful fault boundary. An industrial PC failure may leave the PLC running, provided the control system is designed to operate safely without the PC.
With an EdgePLC, a shared hardware failure can affect both control and computing functions. Process isolation or containerization can help separate software workloads, but it cannot eliminate common hardware failure modes.
If independent operation is a critical requirement, separate devices may be the better design.
④ Resource competition: Can edge applications affect control?
This is one of the most important questions.
Data processing, database operations, network traffic, visualization, and AI inference can consume CPU, memory, storage bandwidth, and network resources.
CODESYS provides the PLC development and runtime environment, but real-time performance depends on the specific controller, operating system, runtime configuration, and competing workloads.
Time-critical control should be engineered and validated independently of best-effort computing tasks. Appropriate resource allocation, task scheduling, workload isolation, and performance testing are essential.
⑤ Real-time requirements: Does the application demand strict timing?
For conventional machine sequences, I/O handling, and supported motion applications, an appropriately configured EdgePLC may offer an effective integrated solution.
For applications with stringent timing requirements, high-axis-count motion, demanding synchronization, or strict functional-safety requirements, the architecture must be evaluated against the actual performance and safety specifications.
Do not assume that a more powerful CPU automatically means better real-time control.
An EdgePLC + CODESYS architecture is worth evaluating when:
You are developing compact machines or standardized equipment.
PLC control and local data processing need to work closely together.
Reducing hardware count, wiring, and integration effort is valuable.
Your edge workload can coexist with the required control tasks.
One platform can meet your I/O, communication, performance, and maintenance requirements.
A separate PLC + industrial PC or gateway may be preferable when:
Control must remain operational independently of the computing platform.
Edge applications have unpredictable or resource-intensive workloads.
Strong fault containment or independent maintenance is required.
The application needs computing resources beyond the selected EdgePLC's capabilities.
Existing PLC infrastructure is established, validated, and economical to maintain.
A hybrid architecture is also possible: use an EdgePLC for machine control and local processing, while keeping higher-level analytics or enterprise applications on a separate industrial computer or server.
The goal is not to minimize the device count at all costs. It is to minimize unnecessary complexity without compromising the system's requirements.
The BLIIOT EdgePLC family is designed for applications that need to bring industrial control, connectivity, and edge computing closer together.
With supported configurations, CODESYS provides an IEC 61131-3 programming environment for control applications, while the selected EdgePLC hardware provides the computing and connectivity resources required by the project.
Different hardware platforms are available for different application requirements, from conventional industrial control to more demanding edge-processing and AI-enabled applications.
For machine builders and system integrators, the practical question is not simply whether one device can replace two.
It is whether one well-designed platform can meet the control, computing, communication, and maintenance requirements of the entire machine.
That is where a careful architecture review makes the difference.
The best architecture is not necessarily the one with the fewest controllers. It is the one that puts each workload in the right place.
Integrate when it reduces complexity without compromising performance or reliability.
Separate when independent operation, resource isolation, or system requirements justify the additional hardware.
Before choosing, evaluate your real-time deadlines, computing workload, failure scenarios, and long-term maintenance plan.
What is your preference for a new machine design — PLC + IPC, EdgePLC + CODESYS, or a hybrid architecture? And what is the deciding factor in your projects?
Let's discuss.
Explore BLIIOT EdgePLC solutions: https://www.bliiot.com/collections/edgeplc-controllers
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