The Power of PLCs: Comparing Allen Bradley and Omron

Introduction

Programmable Logic Controllers (PLCs) are special-purpose digital computers widely used in industrial automation applications to control machines and processes. They accomplish this by continuously monitoring and receiving information from field input devices, such as sensors, limit switches, pushbuttons, etc. On processing the received data and based on their programmed internal logic, they trigger the appropriate field output devices, like motor starters, indicator lights, relays, etc., to complete the specified control task in the industrial process or machinery.

PLCs are simply the workhorse of industrial automation, as they can be programmed to monitor and control a wide range of industrial machinery/equipment, including conveyor systems, robotic devices, production lines, elevators, assembly lines, food processing machinery, etc.

As the industrial automation landscape evolves, many PLC manufacturers leverage advanced technologies to develop high-performance, high-speed, and scalable PLC solutions to keep up with the rapid technological changes and stay at the forefront of the automation curve. But like any other device, not all PLCs are built alike; each PLC brand available today has its features and benefits. In this article, we’ll compare two powerful PLC brands: Allen Bradley and Omron.

Factors to Consider when Selecting a PLC

Allen Bradley and Omron PLCs are available in different types and sizes for almost any industrial automation application. As such, there are various factors you should take into consideration to help narrow down which PLC brand or type would be the best option for a particular application. These include:

• CPU Speed: The CPU speed required of the PLC you intend to use will be determined by how big the system to be controlled is and the response rate it requires.

• Memory Capacity: What size of PLC memory will be enough? Will the application require an external memory module to be added to the PLC system?
• PLC Redundancy: Will the application require any level of redundancy? Is a redundant PLC system needed?  Will the redundancy be independent or synchronous?

• I/O Count: The I/O capability of a PLC refers to the maximum number of unique input and output devices it can scan and control, respectively. Therefore, when selecting a PLC, ensure that you review the number of input and output devices it will need to monitor or control at any given time. Also, will the PLC be required to connect to remote or external I/O interfaces? If yes, select the appropriate accessories to establish the connection.

Generally, PLCs are grouped into the following primary categories based on the maximum number of inputs and outputs they can handle:

• Nano PLCs: These can handle a maximum of 32 I/O functions.
• Micro PLCs: They offer up to 128 I/O points.
• Small PLCs: These are available with up to 256 I/O functions.
• Medium and Large PLCs: These PLCs control many discrete elements, more than 256 I/O points, using speedy I/O scan times.

• Communication Protocols: What field devices, programming terminals, other PLCs, SCADA systems, HMIs, or industrial controls will the selected PLC need to communicate with, and what communication protocols will be used? Examples of PLC communication protocols include EtherNet/IP, PROFINET, DeviceNet, Profibus, ControlNet, SERCOS interface, Modbus Plus, DF-1, EtherCAT, and CANopen.

• Hardware and Software Compatibility: Will the PLC control system be built from scratch? Or will it need to interface with existing control hardware and software?  Is the system being built from scratch, or does it need to interface with existing hardware and software?

• Special Functions: Will the selected PLC be required to have the capability to execute unique functions, such as robotics, motion control, or safety-related functions, in addition to standard control?
• Reliability: Is the PLC system expected to operate reliably with little or no downtime, like in mission-critical applications? What is the expected service life for the PLC system? 

• Scalability: Can the selected PLC system be scaled up or down to accommodate the future needs of the application?

• Environmental Considerations: What environmental conditions will the PLC be subjected to? Will it require special features such as an extended operating temperature range, conformal coating, or a more rugged option for extreme environments?   

• Cost: What is the budget cap for deploying the PLC system? Have the expenses been considered collectively for the entire PLC system, such as the cost of purchasing the PLC hardware, software licenses, installation, programming, integration with existing automation systems/plant, maintenance costs, tech support charges, and any expenses for future upgrades?

Overview: Allen Bradley PLCs

Rockwell Automation offers a wide variety of PLC systems under the Allen-Bradley brand name to meet the specific needs of every automation application – from large-scale to small-scale and even micro-control applications. Available Allen-Bradley PLC control systems are classified as follows:

• Large PLC Control Systems: These include ControlLogix^® 5570 control platforms, CompactLogix^™ and Compact GuardLogix^® 5380 process controllers, and ControlLogix^® and GuardLogix^® 5580 controllers.
• Small PLC Control Systems: Examples of Allen-Bradley small-sized PLC control platforms include SLC^™ 500 controllers, CompactLogix^™ 5480 controllers, and SmartGuard^™ 600 controllers, enhanced with safety-related features.
• Micro PLC Control Systems: They includeMicro870^® PLCs, MicroLogix^™ 1400 controllers, Micro820^® PLCs, Micro850^® PLCs, Micro830^® controllers, Micro810^® PLCs, and Micro800^™ PLC Plug-in modules and accessories.

Each Allen-Bradley PLC control system type is again divided into different controller types and sizes. For example, the “Logix” controller platform features the following:

• ControlLogix^® PLCs: These are high-performance PLCs intended for complicated and large-scale automation applications. They support many I/O points and provide a broad range of communication options.
• CompactLogix^™ PLCs: These are mid-range PLCs used to execute a wide array of control tasks. They provide a good blend of performance and cost-effectiveness.
• MicroLogix^™ PLCs: These are small, low-cost PLCs suited for small to medium-sized automation applications.

Overview: Omron PLCs

Omron Corporation offers many high-performing PLC options for almost every application, from small-scale production lines to large-scale manufacturing processes. These PLCs feature advanced communication networks and multi-axis motion control capabilities and are capable of robotics, sensing, vision systems, and safety control. They are also highly flexible and relatively easy to integrate with other systems, but they only feature software-based redundancy.

Omron PLC models are generally available in three categories, namely:

Compact PLC Series

These are integrated PLC systems in which all the PLC modules(e.g., CPU, I/O modules, power supply units, communication cards, etc.) are housed in a single casing. They feature an integral CPU unit with connection ports, an in-built power supply, and a fixed I/O count and are appropriate for small automation tasks. Examples of compact-type PLCs from Omron include CPM1A PLCs, CPM2A brick-style PLCs, CP1E high-speed controllers, and CP1L high-performing PLCs.

Modular PLC Series

These types of PLCs allow for expansion and customization of the PLC system through the use of different modules, i.e., you can expand the I/O capacities of the PLC system using additional I/O modules and also include peripheral devices such as A/D (Analog to Digital) signal converters. A modular PLC typically comprises multiple modules connected to a standard PLC chassis, such as CPU units, power supply modules, I/O modules, etc.  

The modular PLC series from Omron gives users more flexibility, and it features the following types of PLCs: CJ2M-CPU1 simple-type PLC, CJ2M-CPU3 standard-type PLC, CJ2H-CPU6 high-end controller, CJ2H-CPU6-EIP PLC with a built-in high-speed EtherNet/IP port, CJ1M PLC series, and CJ1G/CJ1H PLC series.

Rack-mount PLC Series

Rack-mounting PLCs are similar to modular PLCs, but unlike in modular PLC systems where each module is directly connected to the base unit, in rack-mount PLC systems, the modules (e.g., I/O modules, communication modules, CPU units, power modules, etc.) are held separately in well-organized racks and can be individually removed and re-inserted as needed. Expansion modules are connected through a communication network.  Omron’s rack-mount PLCs include: CS1H/CS1G PLCs, and the CS1D PLC model

The latest range of PLC offerings from Omron Corporation include:

• NJ-Series PLCs: Omron’s premium PLCs are designed for advanced motion control and high-end automation applications. They provide exceptional performance and scalability.
• NX-Series PLCs: These are mid-range PLCs that heavily emphasize speed and precision. They find applications in different industrial processes.
• CP-Series Compact PLCs: These small-to-medium-sized PLCs provide a cost-effective control solution for medium-sized to small applications.
• CS-Series Rack-mount and CJ-Series Modular PLCs: Omron’s legacy PLCs are still used in some automation applications.

Allen Bradley vs Omron PLCs

Rockwell’s Allen-Bradley PLCs and Omron PLCs are two of the world’s most widely used programmable controllers in industrial applications– and while each controller is irrefutably an industry staple, there are several significant differences between the two PLC brands. Let’s look at how they stack up against each other.

Hardware Features

Let us examine the hardware components of Allen-Bradley and Omron PLCs in terms of essential features, architecture, and typical use cases.

Processor/CPU Units

Under the Allen-Bradley brand, Rockwell Automation PLCs use a variety of processors with variable processing rates, usually centered on the ControlLogix or CompactLogix platforms. These processors provide high-speed data processing and are well-suited for sophisticated control applications.

Similarly, Omron PLCs, such as those in the CP1, CJ2, and NX series, are also available with various processor alternatives. These processors perform standard control tasks and other control functions efficiently.

Memory Options

Allen Bradley PLCs have a comprehensive range of memory options; for example, the ControlLogix^® PLC series includes RAM and flash memory options. This provides a significant memory program and data storage capacity.

Likewise, Omron PLCs come in various memory sizes, with specific models offering expandable memory capabilities. Flash memory in Omron PLCs is commonly used for storing programs and data logging.

I/O Modules

Allen-Bradley PLCs are well-known for their I/O versatility. They provide a broad range of I/O modules, including digital and analog input/outputs and specialized modules for safety-related functions and motion control.                                  

Also, Omron PLCs are available with multiple I/O choices that include digital, analog, and communication modules. For example, Omron’s NX-series provides high-speed standard and safety I/O capabilities and motion control.

Programming Software

Allen-Bradley PLCs use RSLogix 5000 and Studio 5000 as their primary programming software. While the older PLC versions can be programmed using RSLogix 500 software. The Studio 5000(formerly referred to as RSLogix 5000) software provides a user-friendly PLC programming and configuration environment. It also offers advanced simulation and debugging tools.

On the other hand, Omron PLCs are programmed and configured using the CX-Programmer and Sysmac Studio software tools. The CX-Programmer is integrated into the CX-One software package, which includes various features to accelerate the development of PLC programs. The Omron Sysmac Studio is a modern, user-friendly programming and development interface with drag-and-drop capability. Simulation and debugging tools are also available with Omron’s CX-Programmer and Sysmac Studio but may have a slightly different workflow than those offered by Allen Bradley’s Studio 5000 Logix Designer^®.

Programming Languages

Most PLC manufacturers usually provide a programming environment and specify the programming language to program and configure their PLCs.

Allen Bradley:

Rockwell Automation’s RSLogix 5000/Studio 5000 programming environment for Allen-Bradley PLCs supports the following IEC61131-3 PLC programming languages:

• Ladder Logic (LL): This is the most commonly used programming language with Allen-Bradley PLCs. It is a graphical PLC programming language that looks like electrical relay schematics. Ladder Logic is ideal for programming almost all PLC-based control systems as it is easy to grasp, especially for people with an electrical engineering background.
• Structured Text (ST): This is a high-level text-based PLC programming language similar to Pascal or C. It’s more adaptable than Ladder Logic regarding sophisticated calculations and complex algorithms.
• Function Block Diagram (FBD): FBD is another graphical programming language you can use to program Allen-Bradley PLCs. It allows users to define the PLC system control logic using function blocks visually.
• Sequential Function Chart (SFC): SFC is frequently used to program Allen-Bradley PLCs for sequential control. It is a graphical language that aids in organizing complicated automation processes through states, transitions, and actions.

Omron:

Since the CX-Programmer – the programming and configuration software for all Omron PLCs– is integrated into the CX-One software package, advances in CX-One version 4.0 enable users to program Omron PLCs using any of the IEC 61131-3 PLC programming languages, including:

• Ladder Diagram (LD): Like with Allen-Bradley PLCs, all Omron PLCs are primarily programmed using Ladder Diagram, a graphical programming language resembling electrical relay schematics. As mentioned earlier, this makes programming and troubleshooting the PLCs easier for engineers and technicians familiar with electrical relay schematics.
• Structured Text (ST): Omron PLCs also support Structured Text for highly complex logic functions and calculations. It is helpful for sophisticated computations and custom PLC algorithms.
• Function Block Diagram (FBD): FBD is also provided in Omron’s CX-Programmer development environment. It creates modular and reusable graphical control logic using pre-defined function blocks.
• Sequential Function Chart (SFC): Similar to Allen-Bradley PLCs, Omron PLCs support SFC programming for sequential control. This PLC programming language is suitable for modeling complex sequential processes.

Note: Your project objectives, platform familiarity, and hardware compatibility determine the decision to choose either an Allen-Bradley or Omron PLC based on the supported programming languages. The system requirements and hardware features of an application can also influence the choice of the PLC programming language.

Communication Protocols and Networking

Allen Bradley PLCs support an extensive range of communication protocols and networks, including EtherNet/IP, ControlNet, Profibus, DeviceNet, Universal Remote I/O (RIO),   DH+ (Data Highway Plus), DH‑485 industrial LAN, FOUNDATION Fieldbus, HART networks, PROFIBUS-PA networks, etc., and a variety of third-party networks. As a result, Allen-Bradley PLCs can seamlessly integrate with a diverse range of industrial devices and networks.

Similarly, Omron PLCs support diverse communication protocols and networks, enabling them to communicate with other industrial equipment and systems efficiently. Some of the communication protocols and networks supported by Omron PLCs include PROFINET-IO, EtherNet/IP, CompoBus/S, DeviceNet, Profibus-DP, CC-Link, and Modbus TCP/IP, making them appropriate for industrial networking. They also support USB, serial (RS-485, RS-232, and RS-422), and wireless communication methods.

Redundancy and Reliability

Various Allen-Bradley PLCs, such as the ControlLogix® PLC Series, have redundancy options for more excellent system reliability. Redundant PLC-based control systems and I/O modules are employed to reduce downtimes and increase system availability.

Omron provides redundancy features in several of its PLC models to enhance system reliability. These features are frequently applied in applications with critical functions where downtime cannot be tolerated. For example, the CS1D Omron PLC model adds two dual-redundancy options to the CS1-PLC architecture to ensure round-the-clock operation with minimal or no downtime.

Also, some Omron PLCs include dual power supply units and duplex CPUs, with or without loop control functions, to increase system availability. With duplex CPUs, all programs and data stored in the active CPU module can be automatically transferred to a standby CPU module to synchronize the CPU units. So, if an accidental error occurs in the functional CPU module, the standby CPU module can take control immediately (within one cycle time).

In a nutshell, Omron provides a diverse range of duplex PLC system configurations to match various system requirements. For example, you can create redundant communications via Ethernet or Controller Link besides the duplex CPUs and dual power supply units.

Pricing

Allen Bradley PLCs are often perceived as relatively more costly than some competitors. For instance, an Omron PLC system (including hardware and software components) would cost approximately 1/10^th of an equivalent Allen-Bradley PLC system.  However, Rockwell Automation customers consider the advanced features of Allen-Bradley PLC products and Rockwell’s extensive support network as a justification for the higher pricing.

It is safe to say that the pricing for both Omron and Allen Bradley PLCs varies depending on the specific PLC model and its features. For example, Omron’s CP-Series tends to be more cost-effective for smaller automation applications. At the same time, Allen Bradley’s CompactLogix^™ and ControlLogix^® PLCs are highly acknowledged for their robust features but may come at a higher price. 

Tech Support

Rockwell Automation has a huge user community, and it provides substantial documentation and tutorials for its Allen-Bradley PLC product line. The company also offers around-the-clock technical assistance for PLC programming, configuration, installation diagnostics, and troubleshooting services for its PLCs via its official channels. Rockwell’s technical support charges are based on the amount of installed PLC hardware.

Omron also provides extensive documentation for its PLCs, a standard support system, and free resources to assist users of their PLCs. Nevertheless, the extent of Omron’s training and tech support may vary by region. PLC troubleshooting support is free to Omron’s customers during regular business hours.

Industry Focus and Global Presence

Allen Bradley PLCs find application in a wide range of industries, including manufacturing, automotive, pharmaceuticals, wastewater treatment, and oil and gas. Rockwell Automation, the manufacturer of Allen-Bradley PLCs, is a well-established global industrial automation player with a strong presence in North America and other regions.

In contrast, Omron PLCs are mainly used in robotics, packaging applications, food and beverage processing, electronics manufacturing, and automotive assembly lines. Omron Corporation is also a global automation company with a strong presence in Asia and Europe, but it may have a slightly smaller footprint in North America.

Environmental Specifications

When evaluating the environmental ratings of a given PLC system, it is essential to review the recommended ecological conditions under which it will operate reliably, as well as the specified protective enclosure ratings and their suitability for various working environments. Here’s a detailed comparison of the environmental specifications for Allen-Bradley and Omron PLCs:

Operating Temperature Range

Allen-Bradley PLCs feature a broad operating temperature range, usually ranging from -25°C to 70°C or greater for some versions. As a result, these PLCs are suited for indoor and outdoor uses in various industrial environments.

Omron PLCs also have an extended operating temperature range, typically ranging from -10°C to 55°C. While this temperature range is appropriate for many industrial applications, it may not be as broad as some Allen-Bradley PLC models.

Relative Humidity

Allen-Bradley PLCs are built to withstand extreme humidity levels, with many versions rated for up to 95% relative humidity.

Omron PLCs are also humidity tolerant, with typical ratings of 85% relative humidity.

Shock and Vibration Resistance

Allen-Bradley PLCs are designed to withstand mechanical shock and vibration, making them appropriate for physically demanding applications.

Omron PLCs are also built to handle shock and vibration; however, the mechanical shock and vibration tolerance ratings differ between the Omron PLC models.

Hazardous Environments

Some Allen-Bradley PLCs can be utilized in hazardous environments, such as those containing explosive gases or dust. Such PLCs may include ATEX or UL Class I, Division 2 certifications.

Omron also provides certified PLCs for use in hazardous locations, such as industrial environments with highly explosive chemicals.

Specialized Environments

Both Allen Bradley and Omron offer PLC products that are more robust and well-adapted for extremely harsh environmental conditions such as maritime applications and offshore drilling.

Final Thoughts

It is easy to opt for an Allen Bradley or Omron PLC based on one feature or another. However, reviewing the entire PLC package – hardware and software features, ease of programming and installation, supported communication protocols, integration, redundancy, reliability, environmental ratings, pricing, and after-sales tech support– is more important when purchasing.

For example, Omron Corporation offers relatively lower cost options for its PLC hardware, software, and licenses compared to other PLC manufacturers. However, when considering a complete Omron PLC system, additional programming and configuration time is often required due to the nuances of the CX-Programmer programming environment; as a result, the benefits of cheaper PLC components (hardware and software) may be offset by additional engineering costs.

Ultimately, the suitable PLC, regardless of the manufacturer or brand popularity, is the PLC system that meets all the requirements for the given application.

This entry was posted on October 22nd, 2023 and is filed under Allen-Bradley, Automation, Hardware Comparison, Omron, PLC, Technology. Both comments and pings are currently closed.