There’s no single way to build an automation system. As engineers and end users, we have a variety of choices to make when it comes to nearly every component of an application. This is especially true for controllers and motion systems. Do you go with a safety PLC or standard PLC? Do you even choose a PLC? Is it better to go with a PC-based system? As if the choices weren’t plentiful enough, and although PC and PLC systems are the industry standard, there is another choice: microcontrollers. But are microcontrollers like Raspberry Pi and Arduino worth your time, and are they a good choice for your application?
Today we are comparing microcontrollers and PLC systems.
What is a PLC System?
A PLC (programmable logic controller) is an industrial computer used to monitor input devices and make certain decisions based on a previously input program. This generally controls some type of manufacturing or industrial process. In essence, a PLC is the control system behind an application.
Most PLCs are versatile and can generally be used to control nearly anything an engineer will need it to within the system. Most types of hardware and brands can be used with most modern, mainstream brands of PLCs.
Why Use PLCs?
There are three main benefits of using a PLC: versatility, ease of use, and durability. PLCs can be used in nearly any automation system. They are made to connect with a wide variety of sensors and devices and generally do not need any type of external conversion. They also come with a lot of built-in features and capabilities, making them fairly easy to use within a system. There is not a lot of user-required programming needed to use a PLC. They can quickly be mounted, plugged in and used within a system.
PLCs are also durable and long lasting. They are specifically designed to be used in rugged industrial environments. They generally do not need to be encased or protected from shocks, vibrations, corrosion, dust, and other environmental factors that are very common in industrial settings. These machines are able to run for decades in even the harshest industrial environments.
The Drawbacks of PLCs
While PLCs are versatile, durable and easy to use, they do have their drawbacks, the largest of which being the cost. Although they are powerful and make things easy, they do not come cheap, and engineers looking to run a small automated process may not be able to justify their price tag. While this isn’t generally a problem for large-scale machinery, smaller, high volume, and perhaps less complex machines may require an alternative automation control solution.
The second drawback comes in the form of program flexibility. Although PLCs are versatile in that they can be used with a wide variety of products, they generally run on a limited set of programs, commands, routines, and instructions. These limitations make it hard to create a customized control solution for an automation system. Those well versed on coding may prefer to use a PC-based system or microcontroller, both of which are essentially a blank slate when it comes to creating a control program.
Why Use Microcontrollers?
Arduino and Raspberry Pi microcontrollers are small, inexpensive computers capable of running virtually any program that you can code and place into the device. It’s like PC-based control but run on a very inexpensive and smaller scale. This isn’t to say that microcontrollers lack capability; they can be used to control a smaller industrial/commercial system effectively.
The main benefits are cost and flexibility in programming. Traditional PLCs strictly run on ladder logic, though some have an enhanced instruction set that includes structured text, function block, sequential function chart, and more. Typically, microcontrollers can run programs coded in a wide variety of languages and platforms. This gives engineers the option to control a system using a language they are comfortable with. Microcontrollers are also cheap; a Raspberry Pi can be purchased for as little as $25. This insignificant cost can be attractive to people who wish to use the device to control very small applications on large commercial applications that do not necessitate a full-scale PLC.
The Drawbacks of Microcontrollers
The main cons of using microcontrollers come back to one point: they simply weren’t designed with industrial environments in mind. Not only are do they use low voltage, they are not often tested for high shock and vibration, wide temperature ranges, and may not be suited for environments where corrosion, condensation, electrical noise, and dust are prevalent. If you are considering using a microcontroller instead of a PLC, you will have to invest significant amounts of time and money in environmental testing to ensure it will meet the requirements to work in your application.
Microcontrollers generally are not built to handle external errors, so they can easily become stuck in an infinite feedback loop during a process – this requires an extra level of program/system level programming and management. Although they offer a great amount of flexibility in programming, their blank slates mean that they have few pre-programmed solutions for any manufacturing or automation processes. This can be solved by a talented programmer, but those who lack programming and integration skills will find themselves with a powerful little device that is a challenge to use.
Need help choosing a PLC or PC-based controller for your application? Let us help! Get in touch with the automation experts at AMMC today.