Smart I/O and Ethernet connect to and expand fieldbus capabilities
Technology Update: Smart input/output (I/O) devices connected to industrial Ethernet can extend and expand traditional fieldbus functionality, incrementally, as needed.
Sensor level fieldbus communications eliminated the need to return sensor wiring to a centrally located "main" control cabinet. Advantages include less labor, lower physical wire and conduit requirements, faster installation time, and dramatic space reductions. As these fieldbus networks have evolved, so has the capacity to transmit more data more quickly, which enables very large systems to be more tightly controlled. The EtherCAT industrial Ethernet system has low microsecond-level communications ability and the broadest device selection from numerous major vendors.
Gateway terminals permit connectivity with every major fieldbus in use today. Additionally, data transferred from a "traditional fieldbus" to EtherCAT preserves the data and fieldbus characteristics of each traditional fieldbus. EtherCAT I/O users can migrate from fieldbus to advanced industrial Ethernet incrementally as time and budget allows, with wide connectivity to field devices, such as sensors.
Special function (or "smart") I/O solutions communicate at higher speeds and bandwidth to include extra diagnostic information available via the EtherCAT protocol. A prerequisite to using the new special function I/O technology is to ensure the industrial network provides as much speed and bandwidth as possible. With microsecond-level performance and connectivity to many networks, the standard EtherCAT fieldbus network and related I/O system can handle extra process data very well.
Special function I/O devices pair well with EtherCAT and other smart networks. For example, special functions normally handled by separate dedicated devices can be integrated into I/O cabinets with "regular" analog and digital I/O for basic data acquisition. The special function I/O varieties can include more robust measurement of values, such as energy, temperature, vibration, position, angle, and others. Special function I/O devices also can act as a system's safety PLC and amplifier for motors, such as servos, steppers, and dc motors. This is made possible through the continued miniaturization of electrical components and the ability of PC-based controllers to act as the master controller and manage control functions on the machine and/or line. By centralizing the main control and distributing special function I/O, engineers can take advantage of a unified programming environment for PLC programming, safety, and condition monitoring systems. This allows engineers to focus more on the process of a machine or plant rather than various vendors' software platforms.
Since the special function I/O terminals are in the same format as "regular" I/O, they can be installed with minimal wiring effort, sliding together on the same DIN-rail-mounted I/O segment. If a machine-builder or manufacturer can eliminate stand-alone devices that previously handled safety, measurement, and other functions, there can be additional benefits generated from fewer or smaller electrical cabinets. That leads to a smaller machine footprint and the ability to commission more machines in less space and less time, allowing use of a smart fieldbus (industrial Ethernet) and smart I/O.
- Kurt Wadowick is I/O and safety specialist, Beckhoff Automation. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske(at)cfemedia.com.
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