Five reasons to switch to distributed modular I/O

For machine builders there is a great demand to increase the productivity and flexibility of their machines, while maintaining healthy margins. This can be a difficult balancing act between using the most effective technology while working within a shrinking budget.

Distributed I/O systems connected to an industrial network allow for I/O data to be spread across the machine and outside of the cabinet, reducing the total component and hardware costs of the system. New developments in distributed I/O technology have lowered the cost per point of the controls design and have reduced the time to integrate.

A brief market summary

Discrete inputs and outputs have been the workhorse of industrial automation since engineers first started putting sensors and actuators on equipment. Today, the market demands more information from every level of the manufacturing process. Current sensor technology and controls devices allow for this level of detailed information to be collected; however, the challenge for every engineer is that these controls solutions must be cost-effective and simple to implement.

Interest in industrial networks is growing every year and the main swell of interest is in Industrial Ethernet solutions. However, many people find there are some major barriers to using an industrial network. Many believe that the cost of implementation and the lack of internal resources present barriers to the deployment of an industrial network solution. This means that end users are looking for Ethernet networks for many reasons including I/O, but they are reluctant because they also need a cost-effective solution.

Cost-effective controls design

The thought of implementing an unfamiliar technology can cause some anxiety for any engineer. That being said, every end user’s needs and demands are different; so an engineer today is looking at ways to add upgrades or options to their machine that are easy to implement and are customisable to the level that end users have come to expect. There are three primary challenges in cost-effectively enhancing a machine’s design: creating value in throughput or uptime, reducing the total cost of the machine and making the machine distinct among the competition.

Our machine is about as fast as it can get.

While most machines are highly productive already, there is always a demand for more throughput. When the limitations are due to mechanical parts or controls on the machine, the reliability and uptime become a point of pain for the end user. Uptime equals real production dollars for all manufacturers and this added value should not be taken lightly. Easy-to-troubleshoot components with clear diagnostic messages allow maintenance crews and operators to get the machine up and running in shorter periods of time, and enable them to implement repairs with less hassle.

The total machine costs just keep going up!

Industrial commodity and material prices are going up, but end users are less willing to pay for these increases — so machine builders are tasked with reducing the cost of engineering, components and machine construction. The quotation process itself can be time-consuming and frustrating. It is important to be able to quote quickly but it is more important to quote accurately. Wouldn’t it be great to be able to specify the same controls components no matter the PLC or industrial network? In development and installation, the labour costs of manufacture, tear-down and set-up (at the end user) can quickly cut into the margin of a project. So how do you reduce the control cabinet costs? How do you reduce the labour costs of set-up and installation?

How do I make my company and my machines distinct?

Access to real-time data and increased productivity are the two primary operational drivers for an equipment specifier’s interest in industrial network solutions. Specifiers are also interested in ease-of-upgrade as well as quality controls — the machine should be able to expand over time or be modified easily to the needs of the individual end customer. But how do I get more feedback, more diagnostics and more data out of my devices? And how do I add flexibility to make the machine distinct from the competition? How have people solved this in the past?

The evolution of distributed I/O

PLC controls have been in use since they gained popularity in the 1970s. Later that decade, demand for distributed controls allowed for inputs and outputs to be collected across the automation process. When looking at the connection between field devices and the I/O there has been an obvious evolution over the last four decades.

Figure 1: Hardwired inputs and outputs.

Hardwired I/O and junction boxes

Originally there were hardwired I/O devices in which every conductor was individually terminated into the controls cabinet, similar to Figure 1. Each sensor had a cable that was run through a cable tray into the controls cabinet; large numbers of sensors or outputs meant large controls cabinets. Hardwired I/O was characterised by full cable trays and overloaded conduits full of wire. Junction boxes, like the example in Figure 2, helped with this issue to a degree but the same cabinet issues existed. Both of these practices are still active and accepted today in many engineering circles.

Figure 2: Hardwired junction blocks.

Industrial networks

The acceptance of the industrial fieldbus in the early 1990s allowed for control systems to step onto an enlightened path. The ability to communicate intelligently between multiple devices and collect more data than ever before has made an industrial network the next step. As shown in Figure 3, this technology reduces many of the I/O terminations down to a single network cable, allowing for smaller cabinet footprints and simplified hardware installation, right on the machine. I/O data is collected outside the controls cabinet, and with an industrial network more data is available on the process and on the health of the machine.

Figure 3: Reducing cabinet space with network I/O.

The next evolution

Historically, industrial networks have had strong connections to PLC brands. Only certain PLCs could communicate over certain networks. Each controls device needed to be selected with a single industrial network and controller in mind to ease the integration efforts. There are various types of data needed from the components of a machine: discrete points, analog channels, valve controls, identification data, diagnostic information, etc. A technology that would allow for a network-neutral state of the controls equipment would make a machine builder more flexible and cost-effective in their design and overhead, no matter the industrial network or controller selected by the end user.

The solution: distributed modular I/O

In attempting to create a more cost-effective machine, while implementing the most effective technology, many engineers are turning to distributed modular I/O solutions for improving their throughput and increasing their flexibility while cutting costs out of their controls design and implementation. By using distributed modular I/O solutions, the I/O ‘slices’ are separated from the network communication and are designed for mounting on the machine in small pockets of distributed I/O.

Different from a block I/O solution, distributed modular I/O is more flexible in the types of data it can collect. While both solutions are set up in a distributed fashion, in a block I/O solution the individual nodes are dedicated to one specific data type: discrete I/O, valve manifolds, identification data, smart sensor configuration. Each data type then requires a node or IP address on the network and requires further network and auxiliary power cabling to be installed. A network utilising distributed I/O alone can expose the network cabling to harsh environments and network failures due to damage. Distributed modular I/O can maintain the industrial network integrity better by keeping the network connections out of the harshest parts of the manufacturing environment.

Figure 4: Distributed modular I/O.

Centralised I/O requires many installation and development hours. A distributed modular I/O solution allows installers to quickly set up and test the I/O hardware since it uses standard connectors and familiar devices. Furthermore, a distributed modular I/O solution allows the user to put the exact I/O device precisely where it is needed on the machine, reducing the number of cable runs back to the controls cabinet.

A proper distributed modular I/O solution is IP67 (outside of the cabinet) and can distribute multiple types of I/O data. Discrete I/O, from proximity switches and photoelectric sensors for example, is collected remotely with industry standard quick-connect connectors. It has the ability to space analog I/O signals anywhere on the machine without an analog card in the controller or a long shielded cable run through the equipment to a cabinet. It can interface with a valve manifold or communicate with intelligent sensors and RFID processors. Distributed modular I/O collects all of this information into one IP or node address and communicates directly with the controller over the industrial network.

Five reasons to switch

A number of important benefits become evident when a distributed modular I/O system is implemented into a controls design.

1. Simplifies the controls quotation process. It utilises the same components for I/O regardless of the PLC brand or industrial network selected. Pricing for controls equipment is standardised from machine to machine, which makes calculations easily expandable.
2. Opens assembly teams to additional projects. Building controls cabinets is skilled work and they are time-consuming to assemble, wire and test properly. An IP67 distributed modular I/O solution can be mounted right on the machine quickly with less labour. Everything is then wired with standard industrial connectors with less time needed for installation. Speed in set-up allows for more projects per year to go through the assembly floor.
3. Maximises spares. Most initial designs include a set of spare I/O points for later development or modifications. Whether the customer wants to add a few sensors to the design or add a single channel of analog to the machine, spares and additions to the design can add major cost to the controls bill of materials. With this solution, spare connections can be a flexible placeholder for any type of I/O until the need arises, without adding any controls cabinet space.
4. Protects network integrity. One important factor in any machine design is to limit the exposure of the industrial network cabling that runs through the machine. By using a distributed modular I/O solution, the network cabling can be kept out of harm’s way and only the individual I/O device cables run into aggressive environments.
5. Reduces total cost per point. The labour involved in parallel wiring a valve manifold or terminating a set of discrete sensors is labour intensive. Analog devices can get expensive quickly with shielded cable runs and costly 4-channel analog input cards, especially when there is only a need for one analog channel. Distributed modular I/O reduces the labour required in hardware set-up and can be customised to reduce I/O hardware costs.

How distributed modular I/O works

Think of a remote ‘slice’ I/O solution. In a typical application, the communication head and the power supply sit on the left-hand side and then they are followed along the backplane by the individual I/O devices. Usually there are a limited number of slots available in the backplane and individual slices of controls components can be inserted (discrete 24 V input cards or 0-10 V analog cards, for example). In a similar fashion, a distributed modular I/O system has a communications head that talks over an industrial network on one side and collects data as a ‘master’ device on the right-hand side. In the case of IO-Link, each ‘slave’ device is connected to an industry standard M12 port utilising a simple 3-wire sensor cable for communication. With the ability to be installed within a 20 m radius from the master device in any direction, slave devices can be easily distributed across the machine, in close proximity to the sensors and actuators that are wired to them.

Utilising a widely accepted open point-to-point technology, IO-Link is fieldbus independent, is easily configured and is vendor neutral. Process data shows up as simple packets of bytes in the controller for easy integration. There is no need to manually go to each device to configure it, reconfigure it or extract asset management information from it — the devices can be quickly configured using simple read/write commands.

IO-Link has been likened to the well-known USB interface. Both are cost-effective serial point-to-point connections for signal and power transmission and are designed for plug-and-play installation. IO-Link offers everything needed to assume a similar role to USB as the installation system for connecting sensors, actuators, controls and display elements in machine building, and offers downward compatibility to non-IO-Link capable standard sensors, immunity to interference as well as the use of unshielded standard 3-conductor cables.

*Will Healy III is a network and connectivity market manager for Balluff North America, based in Florence, KY.

Image credit: ©ZStoimenov/Dollar Photo Club