Battle of Giants - Differences of PLC by Siemens, Allen-Bradley and ABB

Many industrial equipment manufacturers in the world are producing PLC. The product and market competition between different companies is unavoidable. While top companies receiving great popularity for their products, the clashes and differences between them are always notable too.

Many industrial equipment manufacturers in the world are producing PLC. The product and market competition between different companies is unavoidable. While top companies receiving great popularity for their products, the clashes and differences between them are always notable too.

What is PLC?

Before PLC appeared, industrial control system was called relay contactor control system. The shortcomings of the traditional relay control system are very obvious: complex wiring, long period for design and manufacturing, difficult maintenance, too many adaption troubles, limited functions and so on.

Programmable Logic Controller (PLC) is a digital operation system, specifically designed for application in the industrial environment.

It uses programmable memory to store the instructions of logic operation, sequence control, timing, counting and arithmetic operation. By digital and analog input and output, PLC can automatically control various types of machinery or production process.

At present, in addition to artificial intelligence, computer-aided design and manufacturing, PLC has become one of the three pillars of modern industry. PLC usage has become a standard to measure a country's level of industrial automation.

The world's top companies usually claim a goal to define the industry, lead the world's development and benefit all humans. In fact, good companies and quality products do.

Here, we will discuss three top PLC manufacturers around the world: Siemens, Allen-Bradley and ABB.

Hopefully, this article can make clear their differences for you. As technicians, engineers and programmers, you can have many choices of PLC manufacturers. The choice depends on your aim, so you may need to be familiar with different PLC brands.

Some people probably choose to use devices from multiple manufacturers in one application environment. Let's sort out the three major brands, and see what the differences between them are.

Siemens PLC

Siemens may be one of the most famous manufacturers in the field of automation and PLC. It provides SIMATIC (Siemens automation) series controller so as to meet different performance requirements of users.

Siemens plays an important role in industrial automation and manufacture. SIMATIC controller is designed with excellent standard functions, which can easily be connected with Ethernet TCP/IP and communicate with PROFINET IO. Process Field Bus (Profibus) is included too and users can easily to add functional modules.

When it comes to SIMATIC software, Siemens claims that it is extremely efficient throughout the automation process. Through SIMATICSTEP7, users can configure, program, test and diagnose advanced and distributed controllers. Siemens platform is familiar to programmers and engineers around the world, so it has been a solid choice.

Allen-Bradley (AB) PLC

One of the largest PLC manufacturers in the United States is Rockwell Automation whose Allen - Bradley (AB) series controller is well known worldwide.

AB series provides controllers for projects of all sizes, which is being mentioned as Programmable Automation Controller (PAC). These are based on the automation project.

The controllers can be applied throughout the plant by proper design and plan. And this is achieved by the CompactLogix controllers and software. GuardPLC is used for security systems and SoftLogix software suite.

Allen-Bradley also provides systems for small applications. Among them, Micrologix is most popular, as well as SLC500 and CompactLogix systems.

Allen-Bradley meets the requirements of almost all industries, so its controllers have been installed on equipment of many factories. The programming of Allen-Bradley controller is in the form of RSLogix5000 and advanced Studio5000.
RSLogix series programming software has existed for many years and been developed into a strong automation tool. It is necessary to know about RSLogix and Allen-Bradley in the application of PLC.


ABB is another well-known high-end PLC manufacturer. Its AC500 product is suitable for high-end applications of all scales.
The concept "any module in any CPU" of AC500 series is one aspect that distinguishes it from some other brands. This means no matter what CPU is in your AC500PLC, you can use ABBAC500 module.Therefore, it is easy and affordable to find replacement parts.

The multiple choices of modular equipment is a common characteristic of the three manufacturers. All of these brands let customers set up the system according to their own needs.

You can add any number of input or output cards or module combinations required by the application. These manufacturers also offer fixed units in smaller applications. This means that a fixed PLC may have a certain number of inputs and outputs built into the device. These are usually cheaper and suitable for small applications.


Another convenience worth notice is, these brands providing a complete line of devices, including PLC, HMI to switches and motor drivers for the whole project.

Among them, Siemens is probably the most famous in the world that supports all applications.

One of the biggest and most famous manufacturers is Allen-Bradley of Rockwell Automation, whose RSLogix programming software has existed for a long time. And the latest version is Studio5000.

Besides, ABB is another strong manufacturer that has been in the automation field for many years, and its AC500 series provides everything a modern factory may need.

Note that these manufacturers cover all the hardware and software required to complete the automation project from beginning to end. What's more, there are also many other top manufacturers, such as Mitsubishi, Schneider, Omron, etc.

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