Siemens PLC Versus Allen Bradley PLC

Siemens PLC and Allen Bradley PLC – Which is better for industrial automation?

Siemens PLC and Allen Bradley PLC are two of the biggest PLC manufacturers. When Dick Morley invented the first Programmable Logic Controller (PLC) in 1969 up to now, PLCs have been of great contribution to the industrial segment. A PLC which is also known as the industrial computer control system greatly enhances an industrial process while allowing you to easily replicate or change the process. Secondly, it allows you to mix input and output systems for a modular environment.

There are really no two bigger names in industrial automation than Siemens and Rockwell. Both are great companies employing vast armies of people and generating thousands of jobs at distributors, systems integrators and customers. Both have dominated their respective markets for years and years. Both have fought each other tooth and nail for customers all over the world. In no market was the fight more intense than for the auto-motive customers: GM Ford, Chrysler, Fiat and all the rest.

Both have incredibly engaging stories of rags to riches. Two brothers Werner and Wilhelm von Siemens began product development in the early 19th century Germany. Their first successful product, an electrolytic method for gold and silver plating, found great success in the 1840s and 1850s. From plating they moved on to build their own telegraph. That extremely simple and reliable device led to the founding of Telegraphen-Bauanstalt von Siemens & Halske in October of 1847, the company that would later become what we know today as Siemens.

The Allen-Bradley (Rockwell) story is even more compelling. A schoolmate of Lynde Bradley in 1893, knowing of Lynde’s interest in electricity, brought the book “Electricity for Engineers” by Charles Desmond, to school one day. That book and its description of how Carbon plates could be used for variable contact resistance changed Lynde’s life and led to the founding of Allen-Bradley. From that book, Lynde created a crude rheostat which later led to his partnership with Dr. Allen and the forming of the Compression Rheostat Company in 1903. The compression Rheostat company was renamed Allen-Bradley in 1909.

Here is a comparison of these PLC heavyweights.

Siemens PLC Vs Allen Bradley PLC

Hardware between Siemens PLC and Allen Bradley PLC

When it comes to hardware, both these automation tools work the same way and are reliable. They only differ in fewer areas. For instance, when you install the Allen Bradley PLC, you need to connect the Allen Bradley power supply and the Allen Bradley rack as well. Moreover, you need to install additional cards for safety communication ports. Siemens works with any 24V DC power supply. They come with built-in safety communication ports. AB uses American native protocols such as EthernetIP, DeviceNet and ControlNet. Siemens uses European protocols such as ASI and Profibus.

Automation procedure management

Allen Bradley PLC is easy to configure and manage. The intuitive interface allows users to easily monitor and manage the system. Features such as communication with 3rd party hardware, mass production of code and export/import tags from Excel to scada databases make it popular among endusers. On the other hand, Siemens seems to be complex for regular maintenance staff and require more computer programming background. However, it offers more options to program and customize the process. Siemens PLC offers two safety runtime groups. It means you can divide the infrastructure into two groups and set controller parameters with different priorities and time cycles. This ability allows you to program blocks and download them to the PLC without stopping any process. With Rockwell PLC, this is not possible as it supports only one safety group. Siemens also offers more programming techniques such as FBD, SCL, STL, LAD etc. However, high-end AB systems support function blocks as well as multiple programming techniques.

Support & Pricing

While pricing is not the first aspect to compare, it has significant important as well. The AB Rockwell automation system with Allen Bradley PLC is expensive when compared with that of Siemens PLC solutions. For instance, the Compact GuardLogix which is the least expensive product from AB is still priced at a higher level. Siemens PLC offers standard technical support for free. When it comes to Rockwell, technical support charges are based on the amount of hardware installed.

Conclusion

While both these automation systems are similar in most areas, the difference lies in the software segment. Allen Bradley PLC is easy to use and manage but offers limited customization options. Siemens PLC  is comparatively inexpensive, allows you to program the software to customize different program blocks but requires more computer programming knowledge. Rockwell is more popular in the US while Siemens enjoys an international market.

Source: PLC Manual

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