The debate between Arduino and Programmable Logic Controllers (PLCs) is often framed as a battle between a hobbyist board and an industrial workhorse. While that’s partly true, the reality is more nuanced. Both are microcontroller-based systems designed to read inputs, execute logic, and control outputs. The real difference lies not in their basic capability, but in how they are engineered, validated, and supported for their target environments.
It’s true that an Arduino can perform the core logical tasks of most PLCs. You can read a sensor, run an if/else statement, and energize a relay. The real question is: for how long, under what conditions, and with what level of risk?
Detailed Comparison: Arduino vs Industrial PLC
Cost
Arduino boards are extremely low-cost, and even with added I/O shields, they remain inexpensive. PLCs are much more expensive, and software licenses can add thousands.
Ruggedness and Environment
Arduinos are not designed for harsh conditions. They are sensitive to temperature, humidity, dust, and voltage spikes.
PLCs, on the other hand, are engineered for rugged environments and can operate from 0 to 60°C or higher, in high humidity, dust, and noisy electrical conditions.
EMC and Electrical Noise
Arduinos offer minimal built-in protection and are susceptible to interference. Connecting them directly to industrial motors or VFDs is risky.
PLCs conform to strict EMC/EMI standards such as EN 61131-2, including surge protection, optical isolation, and noise filtering.
Determinism and Real-Time Performance
Arduino systems are non-deterministic. The loop execution time can vary, especially when libraries or background processes add delays.
PLCs are deterministic. They guarantee predictable scan times, ensuring a known response time—critical for safety and precision.
Reliability and Longevity
Arduinos use commercial-grade components with shorter lifecycles.
PLCs are designed for continuous 24/7 operation for decades and use components with guaranteed long-term availability.
Certifications and Safety
Arduino boards have no safety certifications. Using them in emergency stops or guard door applications would be unsafe and likely illegal.
PLCs often carry UL, CE, ATEX, and even SIL (Safety Integrity Level) certifications.
Development and Ecosystem
Arduinos have a vast open-source community and countless libraries for sensors, displays, and communications.
PLCs have structured, vendor-supported ecosystems with standardized software, documentation, and technical support.
I/O and Expansion
Arduino expansion is flexible but requires DIY wiring, isolation, and power management.
PLCs offer robust, modular I/O with plug-in modules for every need, often hot-swappable in higher-end systems.
Maintenance and Diagnostics
Arduino systems rely on user-created diagnostics.
PLCs include built-in diagnostics, status LEDs, and detailed fault codes that maintenance staff can interpret quickly.
Skill Set Required
Arduinos require programming knowledge in C or C++.
PLCs rely on electrical engineering knowledge and ladder logic, the standard language in industrial automation.
Where Each Should Be Used
Use Arduino or Arduino-based Controllers for:
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Prototyping and Proof-of-Concept: Rapidly test control logic ideas or sensor integrations before final design.
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Hobbyist and Educational Projects: Home automation, robotics, DIY experiments.
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Low-Volume, Non-Critical Embedded Products: Specialized displays, data loggers, or art installations.
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Benchtop R&D Equipment: Controlling small devices in lab environments.
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When Budget is the Primary Constraint: When a low-cost failure is acceptable.
The Grey Area: Industrial Arduino-Compatible Devices
Companies like CONTROLLINO, Industruino, and others sell Arduino-compatible controllers with rugged housings and industrial I/O. These bridge the gap for small-scale applications that need Arduino flexibility with added robustness.
Use Industrial PLCs for:
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Mission-Critical Industrial Processes: Production lines, robotic cells, packaging, or chemical processes where downtime costs money.
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Harsh Environments: Factories with high EMI, moisture, or outdoor conditions.
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Safety-Critical Functions: Emergency stops, light curtains, safety interlocks.
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Systems Requiring High Reliability and Determinism: Motion control, high-speed sorting, precision automation.
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Maintainability: Plant technicians are trained to troubleshoot ladder logic, not debug C++ code.
Crucial Factors: A Deeper Look
Ruggedness and Time Sensitivity
Arduinos can run fast, but their execution is not predictable. A 100 ms unexpected delay might cause a jam or product defect.
PLCs guarantee deterministic timing. Their scan cycle ensures inputs are read, logic is executed, and outputs updated in a fixed, repeatable time frame.
Electromagnetic Compatibility (EMC)
Placing an Arduino near industrial motors or solenoids can lead to resets, false readings, or permanent damage.
PLCs isolate the logic side using opto-isolators, breaking the electrical path with light, and protecting against spikes and noise.
Certifications
Certifications define what equipment can be safely used in regulated environments.
Arduino boards do not carry system-level certifications.
PLCs are certified for industrial safety standards like CE, UL, ATEX, and SIL.
Conclusion: It’s About Risk and Responsibility
The real question is not whether Arduino can do it—it’s whether it should.
If your project fails, will it just be an inconvenience or will it cause real damage or danger? Are you building a learning project or the main controller for a machine that a company relies on?
Final Verdict:
Use Arduino for prototyping, learning, and non-critical control.
Use PLCs for reliability, safety, and industrial uptime.
Think of it like engines:
The Arduino is the versatile go-kart engine—fast, flexible, and great for experimentation.
The PLC is the heavy-duty truck engine—engineered for safety, endurance, and consistent performance in any environment.
The Arduino Virtuous Cycle of Development
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From Idea to Proof in Hours
Arduino’s biggest strength is rapid development. You can connect a sensor, actuator, and write logic in an hour. This speed is perfect for feasibility tests, algorithm development, and user interface design. -
The Ultimate Software Emulator for Hardware
Arduino boards act as a hardware emulator for your future product. You can test the same firmware that will later run on your custom PCB. It’s the perfect sandbox for testing communication protocols, sensors, and displays. -
The Stepping Stone to Bare-Metal Programming
Arduino doesn’t trap you in its framework. You can integrate direct register-level code for time-critical sections, port projects to Atmel Studio or MPLAB, or even drop the Arduino layer completely for professional embedded development.
From Arduino Board to Industrial Product
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The Brain Transplant
Once your prototype works on an Arduino, you can use the same microcontroller (like ATmega328P) on your custom PCB. -
Designing the Body
Build a PCB that includes the MCU, crystal, capacitors, reset circuit, and the exact sensors and drivers your product needs. Add proper industrial protection: regulated power, opto-isolation, and EMC filtering. -
Flashing the Firmware
You can either include the Arduino bootloader and program via serial, or skip it and program the MCU directly with an ISP for maximum reliability and memory efficiency.
The Power of Democratization
Arduino democratized embedded systems. Before it, microcontroller development required expensive tools and deep expertise. With Arduino, anyone can experiment with hardware ideas using affordable boards and simple software. It has created a generation of innovators who can turn ideas into working prototypes in hours.
The Importance of Electronic Design
The real secret of industrial reliability is not the chip itself—it’s the surrounding electronic design. The silicon is only potential. Circuit design, PCB layout, and component selection turn that potential into an industrial-grade system.
Arduinos are designed for simplicity and low cost, creating a direct unprotected path from the environment to the microcontroller.
PLCs are designed for resilience, using isolation and protection to shield the MCU from electrical hazards.
The Industrial Shield: Key Design Layers
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The Power Fortress
Arduino uses simple linear regulators like the LM7805, which can fail under voltage spikes.
PLCs use wide-input-range switching supplies with TVS diodes and filters that absorb surges from motors and solenoids. -
The I/O Firewall
Opto-isolators break the electrical connection between field devices and the CPU. Screw terminals and industrial connectors ensure vibration resistance and secure wiring. -
The Noise Cancellation Field
PLCs use multi-layer PCBs with dedicated ground and power planes to control EMI and deliver stable power.
Arduinos typically use two-layer boards, which are more susceptible to interference.
The Engineering Trade-Off
Industrial-grade protection increases cost, size, and design complexity. Opto-isolators, TVS diodes, and EMI filters are expensive and require careful layout. This is why PLCs are costlier but far more reliable.
The Core Philosophy
It’s not that the Arduino’s MCU is weak. In fact, chips like the ATmega328P and ARM Cortex-M are often industrial-grade, rated for -40°C to +85°C operation.
The difference is that Arduino boards lack the industrial infrastructure—power conditioning, isolation, and certification—that PLCs include by design.
The Real-World Proof: Industrial Arduinos
Products like CONTROLLINO, Industruino, and Arduino Portenta Machine Control take Arduino’s flexibility and wrap it in industrial-grade hardware:
rugged enclosures, 24V power inputs, opto-isolated I/O, and screw terminals.
They show that the microcontroller was never the weak point—it was the board design around it.
The True Debate: Core vs System Design
The real difference is not in the MCU’s capability, but in the system engineering that surrounds it.
A PLC manufacturer doesn’t just mount an MCU—they build an entire ecosystem of protection, redundancy, and validation. That’s why a $30 Arduino board can never replace a $300 PLC, even if both use similar silicon.
Final Reflection
The Arduino gives you the brain and asks, “What can you create?”
The PLC gives you a fortified, certified system and declares, “This will work, no matter what.”
Both are built on the same foundation of logic and control—but they serve entirely different worlds.
