I/O Systems, I/O Modules

I/O systems and I/O modules: I/O stands for input/output, and an I/O module is a device that connects networks, sensors, controllers, actuators and other devices or transmitters and communicate measurements about the state of a process. If I/O modules include intelligence (a logic device), they are considered smart modules. I/O modules are often described by their function, such as digital or analog, and by the quantities of input or output points they can accommodate. Collectively, the modules, connections and networking integration and logic are the I/O system. Configurable I/O systems use software to change I/O types to fit the application needs.

I/O Systems, I/O Modules Articles

Product advice on how to make I/O smarter

Input/output (I/O) system design with a head station, base unit, and smart elements creates an extremely compact, highly modular, and economical distributed I/O or control platform, according to a company with a Control Engineering Engineers’ Choice Award product.


Learning Objectives

  • Understand 3-step I/O configuration with hardware, base units and I/O interface elements.
  • Explore steps needed to configure, integrate the programming for an I/O system.

Input/output (I/O) is critical in providing data for automation systems. Whether it is I/O signals directly connected on the programmable logic controller (PLC) or distributed over industrial automation networks, data is king. There are many ways to collect this data, but manufacturers need to adapt to ever-changing needs.

This new approach breaks down an I/O system into three major components: The head station, base unit, and “smart” elements. Combined, this type of I/O system creates a compact, modular and economical distributed I/O or control platform.

3-step I/O configuration: Hardware, base units, I/O interface elements

In the construction and configuration of these stations, the first step is the hardware selection, beginning with the bus interface/head stations. These stations are available for all major Ethernet protocols including EtherNet/IP, Modbus TCP, and Profinet. The interfaces transmit the collected I/O data via the preferred Ethernet protocol back to the PLC for processing. If the collected data requires local manipulation, PLC head stations are also available and can be programmable within an open software programming environment.

Secondly, select the required base units, available in four- or six-slot units. This allows users to mix and match density to match the application needs while not wasting precious DIN rail space. These base units snap to the rail and slide left to snap into the head station or base station to its left, locking them together for a strong, robust connection.

Finally, there are the elements that provide the I/O interface. These elements are available for all signal types: digital, analog, relay temperature, encoder, counter, RS-232/RS-485 serial and IOL. The elements snap into any open slot, allowing the user to arrange the I/O signal and any order that best match specific wiring needs. The I/O signals can then be wired to that module and tool-free using push-in wiring technology. If all the available slots aren’t used, they can protect any open slots with slot covers. Empty slots also can be left for future expansions.

The Axioline Smart Elements (SE) from Phoenix Contact make it easy to create a customized I/O station that occupies minimal DIN rail space. In addition to their compact size, Smart Elements are easy to configure and cost-effective. Courtesy: Phoenix Contact USA The Axioline Smart Elements (SE) from Phoenix Contact make it easy to create a customized I/O station that occupies minimal DIN rail space. In addition to their compact size, Smart Elements are easy to configure and cost-effective. Courtesy: Phoenix Contact USA

How to configure, integrate an I/O system

Once the station is assembled and wired on the DIN rail, the last two steps are configuring and integrating the I/O station into the PLC environment. While this step is not always considered during initial design, it is very important to the programmer that they can complete this task. When configuring the I/O station, users need to assign the station and IP address. This is possible either via the physical rotary switched on the head station or with software to assign IP addresses. Some vendors offer freeware to assist with this task.

Once the IP is assigned, the I/O station will restart into “plug and play” mode. In this mode, the I/O will auto read in whatever I/O is connected to the head station. To finalize the configuration, enter the IP address into a PC’s web browser, logging into the head station’s built-in web server. From this interface, disable plug-and-play mode, locking in the current configuration. Also use the PC interface to observe diagnostics data and I/O data mapping. Diagnostics and data mapping can be used for integrating the I/O station.

The final step is integration of the I/O station into the programming environment. Not all environments are equal, but it is best to follow the standards dictated by the major organization, such as ODVA protocols, Profinet and Modbus TCP to ensure compliance. In this compliance, it’s helpful if the system includes all of the required configuration files such as EDS and GSDML files to aid in these steps. An I/O data map included in the integrated web server also can help the programmer locate the individual data bits, bytes or words.

Jason Haldeman is senior product marketing, Phoenix Contact USA. Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media and Technology, mhoske@cfemedia.com.

KEYWORDS: I/O system configuration advice, Engineers’ Choice Awards


How are you using I/O systems to connect and improve operations?

I/O Systems, I/O Modules FAQ

  • What are the types of I/O modules?

    • Digital I/O modules: These modules handle digital signals, such as on/off or high/low signals, and are used for controlling and monitoring binary devices like switches, actuators and sensors.
    • Analog I/O modules: These modules handle continuous signals, such as voltage or current levels, and are used for measuring and controlling process variables like temperature, pressure or flow.
    • Specialty I/O modules: These modules handle specific types of signals, such as frequency or pulse signals, and are used for specific applications like motion control, process measurement or safety. These modules also may handle signals for specific industrial protocols, such as DeviceNet, Profibus, Modbus and others.
    • Configurable I/O modules: These module can be configured to serve the application as needed and can be reconfigured to serve changing application needs or if initially wired incorrectly.
  • What are the major functions of an I/O module?

    An I/O (input/output) module in industrial networking may perform the following functions, depending on application needs:

    • Input processing: The I/O module receives signals from sensors and other input devices and converts them into a format that can be processed by the control system.
    • Output control: The I/O module sends control signals to actuators and other output devices based on the processing of the control system.
    • Data acquisition: The I/O module collects data from sensors and other input devices and transfers it to the control system for analysis and storage.
    • Communication: The I/O module facilitates communication between the control system and connected devices by transmitting and receiving data over the network.
    • Isolation: The I/O module provides electrical isolation between the control system and connected devices to prevent damage or interference.
    • Protection: The I/O module may provide protection against overvoltage, overcurrent, and other electrical hazards to ensure the safety and reliability of the system.
    • Diagnostics: The I/O module may provide diagnostic information to the control system, such as device status and error codes, to aid in troubleshooting and maintenance.
    • Control or pre-processing: So called "smart" I/O modules include a logic device to pre-process, parse, analyze or make a decision about data for control or to prepare data for another controller or control system.
  • Why are I/O systems important to manufacturing?

    /O (input/output) systems are important to manufacturing for several reasons:

    • Data collection: I/O systems enable the collection of data from various sources in the manufacturing process, such as sensors, machines, and control systems.
    • Control: I/O systems provide a means of controlling and automating the manufacturing process by sending signals to actuators and other output devices, or when a logic device is embedded, perform control or pre-processing of data.
    • Monitoring: I/O systems allow real-time monitoring of the manufacturing process, enabling early detection of problems and improving overall efficiency.
    • Flexibility: I/O systems can be configured and reconfigured to accommodate changes in the manufacturing process, providing greater flexibility and adaptability.
    • Safety: I/O systems can help ensure the safety of manufacturing operations by enabling emergency shut-off and other safety functions.
    • Quality: I/O systems can help improve the quality of the manufacturing process by enabling precise control and monitoring of key parameters.
    • Cost savings: By improving efficiency, reducing downtime and minimizing the need for manual intervention, I/O systems can help reduce the costs associated with manufacturing operations.
  • What challenges face I/O systems in manufacturing?

    There are several challenges that I/O (input/output) systems face in manufacturing, including:

    • Interoperability: Ensuring that I/O systems can communicate and work effectively with other systems and devices in the manufacturing process can be a challenge.
    • Reliability: I/O systems must be reliable and perform consistently over time to avoid downtime and lost productivity.
    • Scalability: As manufacturing processes change and grow, I/O systems must be scalable to accommodate these changes and handle increased demands.
    • Maintenance: Maintaining and updating I/O systems can be time-consuming and costly, and requires skilled personnel.
    • Security: Ensuring the security of I/O systems and the data they collect and process is a growing concern, particularly in the face of increasing cyber threats.
    • Integration: Integrating I/O systems into the overall manufacturing process can be complex and requires careful planning and coordination.
    • Environmental conditions: I/O systems must be designed to withstand harsh environmental conditions, such as temperature extremes, dust and vibration, often common in manufacturing applications.

Some FAQ content was compiled with the assistance of ChatGPT. Due to the limitations of AI tools, all content was edited and reviewed by our content team.