Difference Between Allen Bradley And Siemens PLC

One of the biggest boons that the industrial sector of the world at large received came in the last century. We are talking about the invention of the Programmable Logic Controller (PLC) by Dick Morely back in 1969.

Ever since then, there have been many innovations in terms of functionality and hardware features for the control system and needless to say, each new one has been tough to beat. There are predominantly two giants who have had the duopoly in the manufacture of efficient PLCs for a long time now and they are Siemens and Allen Bradley.  


While each of these are established and top notch companies who have already proved the worth of their super-efficient TLCs individually, there has forever been a debate over which of these is better.

So here is a detailed comparison between the Allen Bradley and Siemens PLCs.

Before we begin, a quick word about what a PLC is.

What is a PLC?

In the simplest of terms, a Programmable Logic Controller or PLC is an industrial computer control system that allows you to get the most out of industrial processes. It helps enhance the processes while at the same time allowing you to switch up, replicate or change the processes as well quite easily.

Allen Bradley Vs. Siemens PLC

First things first, the quality and functionality of the hardware are significantly distinct. Both the AB and the Siemens PLCs work pretty much the same way and are equally reliable. The difference lies in their installation processes.

While the Allen Bradley requires you to connect the PLC to both the Allen Bradley power supply as well as the Allen Bradley rack, the Siemens one works with pretty much any 24 V DC supply of power. Also, you might need to install additional safety communication ports for Rockwell while Siemens already comes with built-in communication ports.

Another major difference is in the protocols they use. AB uses mostly native American IPs such as DeviceNet, ControlNet and EthernetIP, and also the DH+ or DH485.

At the same time, Siemens uses European native IPs such as Profibus and ASI and also serial MODBUS or MODBUS TCP/IP.

image3Coming to the interface and ease of use, AB has a more intuitive and easier user interface and it allows users to manage and control their processes even without a lot of programming knowledge. It also has excellent features like communicative abilities with third party hardware, mass production of code and even export and import of tags from Excel to scada databases.

Siemens might be a little complex for the maintenance staff that may not have a programming background.

On the flip side, Siemens offers a lot of options to program and customise the process to suit your business model.


As for the pricing aspects, Allen Bradley definitely is more expensive when compared to the Siemens PLC. However, Siemens offers standard technical support at all times at no additional costs while AB does charge you for technical support according to the amount of hardware you have installed.

That said, it would be ideal to choose one of these according to your priorities in terms of business processes.

Now if you have both Allen Bradley and Siemens devices and you want them to communicate, then you can use Equustek DL3500-MODBUS/DH+ or DL3500-MODBUS/DH485 for All Siemens that can handle uses serial MODBUS and Allen Bradley that support DH+ or DH485, or use the DL6000-MEDH+ or DL6000-MEDH485 that allow Siemens with MODBUS TCP/IP to communicate with Allen Bradley DH+ or DH485 devices.