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.
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.
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
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
CONSIDER THIS
How are you using I/O systems to connect and improve operations?
Want more information on IO Module in PLC, Intelligent Distributed IO? Click the link below to contact us.