Arduino vs PLC: Can We Replace PLC with Arduino?

In the realm of industrial automation, Programmable Logic Controllers (PLCs) and Arduino have long been two different tools used for control and automation tasks. However, the growing popularity and flexibility of Arduino have led many to question whether an Arduino can be a viable alternative to a PLC in certain applications. This article explores the pros and cons of using Arduino vs. PLC and provides insights from real-world experiences in industrial settings.

Understanding PLCs and Arduino

Programmable Logic Controllers (PLCs) are specialized computers used for automation of electromechanical processes in manufacturing or other enterprises. They are designed to control machinery and systems in harsh industrial environments. PLCs typically feature a rugged design, high reliability, and specialized programming languages such as ladder logic to meet the demands of industrial automation.

Arduino, on the other hand, is an open-source hardware and software platform for building digital projects, particularly in embedded systems. It is popular among hobbyists, students, and professionals due to its simplicity, flexibility, and ease of use. Arduino boards are not designed to withstand the harsh conditions often present in industrial environments and may not be as rugged as PLCs.

When Arduino Might Be Overkill

In many cases, using an Arduino might be considered overkill compared to a PLC. This is because:

Programming Complexity: The programming model used in PLCs is generally more complex and designed to handle industrial automation needs. While Arduino has an easy-to-understand programming language, it may not be as robust for more complex control tasks. Reliability: PLCs are built to endure harsh industrial conditions and have a longer lifespan. Arduino boards, on the other hand, may not be able to withstand the same level of wear and tear in industrial settings. Industrial Grade: Arduino boards are not designed for industrial-grade applications. They may fail due to physical, electrical, or magnetic interference in harsh environments.

However, there are scenarios where Arduino can be a suitable and cost-effective alternative to PLCs. This is especially true when customized solutions are needed, or when simple automation tasks are required.

Real-World Applications and Success Stories

Despite the apparent limitations, there are several instances where Arduino has been used successfully in industrial settings:

Case Study 1: Hydraulic Motor Control

My team replaced a broken PLC that had no sources in an industrial setting where 10 hydraulic motors were involved in cutting, bending, welding, and rebar wire operations. The power consumption was in the MW range, and the electromagnetic interference (EMI) was so strong that it would cause an Android phone to reboot. We replaced it with an Arduino-based system using an STM32 microcontroller and GCC firmware. While the native Atollic Studio and STM32Cube Studio are more commonly used, the same MCU could theoretically be used as an Arduino board. The system performed better than the original PLC and lasted for years.

Case Study 2: Temperature and Humidity Controller

A literal Arduino-based temperature and humidity controller replaced a dead PLC in a clean room setting in a glass factory. The environment was clean, both physically and electrically, with minimal magnetic interference. The person who implemented the solution used an Arduino Nano, added sensors, and optoisolated outputs to drive 24V relays. The controller was encased in a proper metal box and functioned flawlessly for years, outperforming the original PLC.

Key Considerations and Limitations

While Arduino can be a powerful tool for industrial automation, it is essential to consider the following limitations:

Customization: Arduino is highly customizable, but this can also mean increased complexity and development time. Reliability: Arduino boards may not have the same industrial-grade reliability as PLCs. Programming: While Arduino has a user-friendly programming interface, it may not be suitable for all types of complex automation tasks.

These limitations mean that the answer to the question “Can we use Arduino instead of PLC?” is not a straightforward “yes” or “no.” Instead, it depends on the specific application, the complexity of the task, and the environment in which the system will be used.

Conclusion

In conclusion, while Arduino may not be a drop-in replacement for PLCs in all industrial settings, there are scenarios where it can be a suitable and cost-effective alternative. With careful planning, customization, and an understanding of the specific requirements, Arduino-based systems can be successful in industrial automation projects.