A Complete Guide to Allen Bradley IO Systems

This post introduces the Allen Bradley portfolio of I/O products. After reading this post, you should be able to;

• List and define the main I/O product lines in the Allen Bradley portfolio,
• Recognize the differences between these product lines,
• Give examples of the factors that drive selection decisions between these product lines.

Note that this post only covers the contemporary products in the I/O portfolio. There are many legacy I/O platforms that are not discussed in this post.

I/O Platform Selection Factors Overview

There are a few factors that go into the selection of the appropriate I/O platform for any given application. One reason that Rockwell Automation has so many I/O product lines is to meet the different requirements of these selection factors.

Let’s look at the different factors that go into selecting an I/O platform for an application.

Local vs Distributed I/O

Does the application require local or distributed I/O?

Local I/O uses a direct backplane connection to communicate with the controller as shown here.

Distributed I/O uses a network connection to exchange information between a controller and remotely located I/O modules as shown here.

In-Cabinet vs On-Machine

In some industries there is a push to move automation products that were traditionally installed inside electrical cabinets to be mounted directly on the machine. I/O in particular has been influenced by this trend.

In order to mount an I/O module directly on the machine, a different design approach is necessary. For example, the I/O module would have to continue working after being washed down, so the design must be water tight.

Rockwell Automation uses the prefix ‘Armor-" to denote products that are designed to be mounted directly on a machine instead of inside an electrical cabinet.

Safety I/O

There are many applications that require the use of special safety rated I/O. This I/O is more expensive than I/O that does not carry the safety ratings, so standard I/O remains popular for applications that are not safety related.

Specialty I/O

There are many types of I/O module, and not every I/O platform includes every type of I/O.

Therefore, what specific modules are required by the application is an important selection factor. For example, not every I/O product line includes HART or I0-Link. If one of those capabilities is required in the application, it is important to select an I/O family that has that type of module.

There are also dedicated specialty applications that drive I/O selection. As one example, there is a special type of condition monitoring equipment to predict motor failure that uses its own, dedicated I/O product line.

Each product line of Rockwell Automation I/O is designed to address these various selection factors.  Let’s look at each in more detail.

Local I/O vs Distributed I/O

Let s compare local I/O to distributed I/O.

Simple applications typically utilize local I/O, meaning that it is either embedded I/O in the controller housing or expansion I/O that is attached to the controller via an electrical backplane.

As applications become more complicated, it is often beneficial to use distributed I/O, meaning that the I/O module itself is remote from the controller. The information is passed back and forth via a network. This can be very helpful if the I/O devices are spread out over a wide area, as it puts the I/O module closer to the devices. This can dramatically reduce wire costs because one network cable replaces what would otherwise be a large group of cables for all of those devices.

Using local or distributed I/O contributes to the decision of which I/O platform to use.

Local I/O Platforms

Nearly every controller in the Rockwell Automation portfolio has a local expansion I/O platform. These are typically referred to as ‘Chassis-based I/O”, whether there is a physical chassis or not. What it really means is that there is a direct connection between the controller and the I/O via an electrical backplane.

The ControlLogix platform is an example of a physical chassis, with both ControlLogix controllers and 1756 I/O (among other modules) installed in a chassis.

By comparison., the CompactLogix that is shown in this picture is an example of 'Chassis-based I/O” where there is no physical chassis. Instead there is just an electrical backplane connection between the controller and the expansion I/O module.

The Chassis-based I/O platforms that are used with Logix controllers can be used either as local I/O or as distributed I/O, meaning that there would be a network adapter connected to the I/O modules in order to send the information to a controller at a remote location.

The lead products in the Chassis-based I/O portfolio for use with Logix controllers are 1756 ControlLogix I/O, Compact 5000 I/O, and 1769 Compact I/O. The main selection driver between these platforms is simply the controller that is being used in the application.

In the component level applications space, the Micro800 platform has its own line of expansion I/O.

Chassis-Based I/O: ControlLogix I/O (Bulletin 1756)

ControlLogix I/O is used with ControlLogix controllers for both local and distributed I/O applications. All ControlLogix modules, including I/O, have catalog numbers start with 1756-.

The image here is an individual ControlLogix I/O module. The I/O terminals themselves are accessed by opening a plastic cover at the front of the module

ControlLogix I/O has traditionally been positioned for large and complex applications and is feature rich.

Another benefit of ControlLogix I/O is that there are network adapters for many different automation networks. (By comparison, some I/O platforms are EtherNet/IP only.)

Chassis-Based I/O: Compact 5000™ I/O (Bulletin 5069)

One of the newest lines of I/O is the high performance Compact 5000 I/O.

You might be asking, “What does ‘high performance' mean?”

One example is the 200 microsecond update rate, which enables superior system speed and precision.

Another is the gigabit (1Gb's) Ethernet network connection for superior network performance as compared to the much more common 10/100 megabit Ethernet.

Many other premier capabilities are designed into this platform, making Compact 5000 I/O ideal for demanding applications.

Compact 5000 I/O is the local I/O and preferred distributed I/O for the high performance 5380 CompactLogix controllers. It is also a preferred distributed I/O for the high performance 5580 ControlLogix controllers.

Compact 5000 I/O catalog numbers start with 5069-.

Chassis-Based I/O: Compact I/O™ (Bulletin 1769)

1769 Compact I/O is used with 5370 and older CompactLogix controllers for both local and distributed I/O applications.

It is less expensive and less advanced than ControlLogix I/O and Compact 5000 I/O.

Distributed I/O

The Chassis-based I/O platforms we’ve discussed so far can be used either locally or in a distributed arrangement with Logix controllers.

There are also several additional I/O product lines that are typically used as distributed I/O for Logix controllers. These additional product lines provide more alternatives to better suit customer needs.

For in-cabinet distributed I/O applications for use with Logix controllers, the additional lead products are FLEX I/O and POINT I/O.

For on-machine applications., the lead product is the ArmorBlock I/O family.

Another term used for distributed I/O is remote I/O.

Distributed I/O: Modular vs. Block

Before we go into more detail on the distributed I/O platforms there is another concept that should be clarified. Distributed I/O platforms are defined as either Modular or Block.

In a modular design, the I/O electronics module, wire termination style, and network interface are separate pieces that the user assembles together.

By comparison, in a Block design all of these components are built into a single housing.

The modular design enables the user to select each of those functions independently. It also makes adding more I/O points easier and less expensive. Generally speaking., the lead products for in-cabinet distributed I/O are modular by design.

In contrast. On-Machine I/O platforms are typically the Block style (with everything built into one housing).

In-Cabinet Distributed I/O: POINT I/O™ (Bulletin 1734)

One of the lead products for in-cabinet distributed I/O applications is the 1734 POINT I/O line. It features a modular design and a wide variety of types of I/O modules.

In this family, each I/O module is narrow. Standard modules are only 12mm wide. This means that a rack of POINT I/O has a small overall footprint. This narrow dimension is possible because it is low density, meaning each module only connects to a few physical input and output devices. Specifically, typical modules have between 2 and 8 channels. This low density minimizes the number of unused I/O channels in any given application, which is beneficial because the user only has to pay for what the application requires.

The narrow width and low density are beneficial in applications that require many different types of I/O modules for the same reasons - less total panel space and less cost than in other I/O product lines.

POINT I/O is generally targeted to machine applications. That said, it can also be found on some process applications. For example, many process skids have low I/O counts and therefore benefit from the low density of POINT I/O.

The POINT I/O platform has a wide variety of types of I/O modules and specialty modules, such as I0-Link.

In-Cabinet Distributed I/O: FLEX™ I/O (Bulletin 1794)

FLEX I/O is a modular, high density I/O platform for distributed, in-cabinet applications.

High density means that each module can have many channels and a large number of I/O channels can be connected to a single network interface. Any application with a large number of I/O devices can benefit from the density offered by FLEX I/O, particularly applications with many analog inputs. This is one of the reasons that it is a popular solution for various Process Automation industries.

FLEX I/O catalog numbers start with 1794-.

In order to achieve the high density, each module is much wider than a POINT I/O module. A FLEX I/O module is 94mm wide and has up to 32 channels. (In companson, POINT I/O modules are 12mm wide with up to 8 channels.)

1794 FLEX I/O is the Process I/O of choice for ControlLogix 5570 Controllers.

In-Cabinet Distributed I/O: FLEX 5000 I/O (Bulletin 1794)

Flex 5000 is Rockwell Automation’s newest edition to the Flex I/O family.

Flex 5000 I/O enhances communication with 1Gb EtherNet/IP connectivity, which offers higher speed and increased bandwidth.

Flex 5000 supports a variety of network architectures including Device Level Ring, linear topologies, star topologies, and Parallel Redundant Protocol, also known as PRP.

Parallel Redundant Protocol, often abbreviated PRP, is a very important standards based (IEC 62439-3) communications protocol used primarily for process applications. It allows parallel ethernet LANs to communicate with the Flex 5000 network adaptor providing a fault tolerant ethernet connection.

Other Flex 5000 enhancements include an ethernet fiber optic connection. Fiber optic networks allow for longer network runs measured in thousands of meters allowing Flex 5000 I/O to be distributed over very large distances.

Additional Flex 5000 I/O improvements include. HART Premier Integration, enhanced diagnostics, faster I/O updates, digital safety I/O, and analog Safety I/O.

Flex 5000 is the distributed, in cabinet process I/O of choice for PlantPAx ControlLogix 5580 and CompactLogix 5380 process controllers.

FLEX 5000 I/O catalog numbers start with 5094-.

In-Cabinet Versus On- Machine™ I/O

Traditionally, I/O modules were always mounted in the controls cabinet. Field devices would connect to individual cables that were all run back to the controls cabinet. Inside of the cabinet, these cables were wired to terminal blocks and then connected to the I/O module, shown here as chassis-based I/O.

This in-cabinet approach to I/O modules is still the norm in most industries. That said, some manufacturers see tremendous benefit to moving automation devices, particularly I/O modules, out of the cabinet and onto the machine.

The graphic here shows this approach, and some of the benefits become clear immediately. The potential for wring mistakes is dramatically decreased. Wiring labor costs are significantly lower. Troubleshooting the system becomes easier. For OEMs, using on-machine I/O means that they can build more machines without increasing labor costs or the size of their facilities.

The trade-off for the on-machine design is that each I/O module is more expensive. This makes sense, since the I/O module must be ruggedized. On-machine products can typically be washed down. The connection points for the cables, which are quick disconnect and therefore easy to use, also contribute to the cost of the on-machine design.

On-machine design is particularly popular in the automotive industry

On-Machine I/O: ArmorBlock® I/O (Bulletin 1732)

The lead product for on-machine I/O applications is the Bulletin 1732 ArmorBlock family.

The picture above shows two example products from that family.

The ‘Armor...' prefix is used on Rockwell Automation products to denote the on-machine design, particularly for products that were traditionally deployed inside control cabinets. ArmorBlock I/O modules typically have connection points for between four and sixteen I/O devices. There are also connection points for the network and for power.

Because the I/O modules are typically daisy-chained., usually there will be two network ports and two power ports, so that each can be passed through to the next I/O module in the daisy chain.

There are many different ArmorBlock modules for a variety of applications.

As on-machine products, ArmorBlock modules are rated IP67 and IP69K and therefore are suitable for wash-down environments. They also feature superior corrosion resistance.

1715 Redundant I/O (Bulletin 1715)

There are certain applications where downtime is so critical that redundancy of the I/O modules is required to minimize downtime as much as possible. If one I/O module were to fail, the redundant unit would take over and keep the system operating with no downtime. In other words, it is Fault Tolerant. The failed module can be replaced without interrupting operation. This capability is sometimes referred to as "High Availability".

For Logix based applications, 1715 Redundant I/O is the product to use when I/O redundancy is required. The competitive advantage of 1715 Redundant I/O is that it is fully integrated - unlike other redundant I/O, it doesn't require special configuration software, complex programming, Add-On Instructions, or cross-wiring of inputs and outputs. In Studio 5000 it looks and feels like any other Rockwell Automation I/O line.

The highly critical applications that require redundant I/O are typically found in various Process Automation applications.

One thing to be aware of about the 1715 Redundant I/O line is that it looks exactly like the I/O used with Rockwell Automation AAdvance Process Safety Controllers, but in fact these are separate catalog numbers. 1715 I/O and AAdvance I/O are NOT interchangeable - they are separate product lines.

Machine Safety I/O: Guard I/O™

Anytime that I/O is deployed as a part of a system that is intended to protect people, it is required to use safety rated I/O that is specifically designed for these purposes. They are designed around a set of standards and design principles to dramatically reduce risk in these applications. These special design considerations, in addition to significant testing and design review by third party organizations, are what earn the product a safety rating.

Machine safety is one type of safety. It is appropriate for applications where off is a safe state. For example, a motor that would be very dangerous if running, is generally not dangerous if it is stopped. So machine safety products are designed to make sure that the motor and other moving parts stop if there is ever an abnormal condition. This principle is straightforward, although it takes significant design effort within the product itself.

One application example would be the use of a light curtain - safety rated I/O would be used to monitor the status of the light curtain.

Allen-Bradley products that are designed and rated for machine safety applications often include the term ‘Guard..." in the product name. For example, machine safety rated I/O in the POINT platform is called POINT Guard I/O.

One nice feature of POINT I/O is that standard I/O modules and safety rated I/O modules can be grouped together and use the same standard network adapter.

Another safety I/O platform that uses a standard network adaptor is Flex 5000. Like POINT Guard I/O, Flex 5000 safety I/O allows a mix of standard and safety I/O using the same standard network adaptor. Flex 5000 offers additional features like more safety points per module and faster I/O update times. Faster update times allow machinery to transition to a safe state in a shorter period of time which is advantageous in most safety applications.

In addition to Point Guard and Flex 5000 Safety I/O, safety I/O is available on the ControlLogix and Compact 5000 platforms. With these platforms, safety I/O can be installed in the controller chassis, as well as remotely on a standard network adaptor.

For on machine safety applications, the ArmorBlock Guard I/O is available.

In addition to the '‘Guard...” naming convention, another thing that denotes the machine safety rating in the Allen- Bradley portfolio is that these products are typically colored red.

It is important to note that Machine safety I/O is only for use with GuardLogix safety controllers. Machine safety I/O is not for use with standard controllers.

Intrinsic Safety I/O: 1719 Ex I/O (Bulletin 1719)

Intrinsic safety is another type of safety application that requires specially designed I/O. Intrinsic safety is the term used for products that are designed to reduce the risk of explosion in explosive environments. Anyplace where flammable gases or dust are present or may be present is referred to as a "Hazardous Location" and requires the use of intrinsic safety rated products.

For example, a propane tank filling station would be considered a Hazardous Location. Examples that might not be as obvious would include paper mills and sawmills, as both paper dust and sawdust are extremely flammable.

One aspect of intrinsic safety products is that they are designed to minimize electrical sparking that could ignite flammable gases or dust.

Hazardous locations are characterized by Classes and Divisions in North America and Zones in the rest of the world.

The Allen-Bradley I/O product for Intrinsic Safety applications is 1719 Ex I/O. It is appropriate for use when connecting to field devices that are installed in areas rated Class I, Division 1 (for North America) or Zone 1 (for the rest of the world).

The rack of I/O modules can be mounted directly in Class I, Division 2 areas or Zone 2 areas.

The I/O modules can also be mounted in Division 1 or Zone 1 if a purged enclosure is used.

Specialty I/O Applications

Beyond the I/O platforms previously discussed there are other specialty I/O products.

One key specialty line to be aware of is the Dynamix 1444 Condition Monitoring line. This system is used to predict machine and motor failures by monitoring vibration and other runtime characteristics therefore enabling preventative maintenance to get ahead of these problems and minimize the risk of unplanned downtime events.

The Dynamix 1444 Condition Monitoring consists of the dedicated I/O platform shown in the image connected to specialty vibration and other sensors. This system connects to a Logix controller to fully integrate this information into the control system.

Comparison Summary

Here is a comparison summary of the key functionalities of and basic differences between the lead I/O platforms. For more detailed information please refer to the product literature.

Note that this summary characterizes each product line as being generally used for either process applications or machine applications. This generalization is helpful for understanding the primary focus of each line, but please be aware that there are numerous counter examples.

For example, even though POINT I/O is typically used for machine applications, it is also a popular choice for Process Skids. Similarly, even though FLEX I/O is primarily for process applications, some machine applications benefit from the high I/O density that the line provides.

Summary

After reading this post, you should be able to:

• list and define the lead I/O product lines in the Rockwell Automation portfolio,
• recognize the differences between these product lines, and
• give examples of the factors that drive selection decisions between these product lines.