Separate HMI and I/O systems are more flexible

HMI and I/O systems offer more options when purchased separately, rather than in an all-in-one product.

By Reid Beilke December 4, 2015

When researching all-in-one human-machine interface (HMI) and input/output (I/O) products, certain features may lead designers and engineers to implement an all-in-one technology. Typically, these all-in-one technologies are selected for the low, up-front costs and compact form factor. In addition, removing wiring time and other installation complexity makes all-in-one HMI and I/O products an attractive option for companies with a need for time or staffing challenges.

After those initial savings are tallied, what happens when you need to expand the design, upgrade systems, or alter current I/O configurations? What complications arise when it is discovered that the on-board I/O count in the HMI hardware is insufficient, or there are more I/O points than really needed? Suddenly, the easy-to-install, simple solution becomes a time-consuming and often costly problem, as most of these systems offer little flexibility or precision for expansion, customizations, or upgrades.

Integration is key

Looking at a hypothetical operation expansion, the flexibility of separate HMI hardware and distributed I/O system architectures offer the ability to add and/or replace DIN rail or machine-mounted I/O modules to meet current needs or swap out the HMI and controller for technology migration or expansion with minimal downtime. With I/O terminals that can offer increments of two, four, eight, 16 or more channels, users can more precisely specify the I/O count required for applications and incrementally add terminals as system needs grow over time. Distributed I/O systems also are better at integrating most networking protocols into one system, allowing companies to use a preferred protocol (or protocols), as well as enabling connectivity with legacy systems.

Technologies that bundle automation and control functionality with PC-based HMI hardware offer high efficiency. As the HMI and control functions are performed in software when PC-based control is implemented, distributed I/O terminals can be changed or expanded upon with the PC control software automatically identifying newly connected terminals upon startup (simple, quickly made changes to the application software may also be required). If more substantial system upgrades must be made, users can copy their code for HMI and control into the new HMI hardware and be up and running in minutes. Compatibility of all kinds of code across standard PC-based processors is the key to this flexibility. Modular, expandable PC-based systems offer unparalleled choice and the easiest migration path for companies whose operations will change in the foreseeable future. In addition, distributed I/O systems are infinitely expandable and can meet the needs of companies which thrive in ever-changing manufacturing environments. 

Bottom line

Controls engineers have far more flexibility to accommodate system changes when the HMI hardware and I/O system are kept separate. The right price point to meet budget demands up front can still be found, without having to start from scratch when production and operations needs change.

– Reid Beilke, industrial PC product specialist, Beckhoff Automation. Edited by Eric R. Eissler, editor-in-chief, Oil & Gas Engineering,

Key concepts

  • Modular, expandable PC-based systems offer unparalleled choice and the easiest migration path for companies whose operations will change in the foreseeable future.
  • Distributed I/O systems are also far better at integrating almost every fieldbus protocol into one system.

Consider this

All-in-one HMI and I/O systems are great for when a system has no plans to expand, but they are bad when the system needs to be scalable, requires upgrades, or needs more inputs. Separation allows for more flexibility.

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