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Do the display panel proud

Dec. 8, 2020
HMI design has come a long way from function keys multi-color screens with animation

When I first started my career with Allen-Bradley in the 1970s, these things called PLCs were all the rage. The revolution had started. Part of the problem though was that the visualization of the process was not as easy as automating the process.

My first “project” was to help a customer to design and build a mimic panel using lamacoid cutouts, lights and a CRT display. We needed to display timer values and analog values, which were accomplished with seven segment displays and meters. However, there was a single ladder rung that had a raft of interlocks in it that needed to be displayed on the CRT since there was no room on the mimic panel for various lights as such.

Remember Panalarm? It was too expensive for this project at the time, so the old tried and true interface of numbers and lights were chosen.

The application was a pre-heat furnace at a steel plant, so the environment had something to do with the product selection. So did what was available.

Operator interface came along a bit later than the PLC as such. SCADA devices were starting to come into the marketplace but were far too expensive to monitor a single application.

Enter HMI panel displays. They were not cheap but were effective. Allen-Bradley had its T30 displays and all offerings had built-in development systems. Remember the PC wasn’t born yet or was at least in its infancy.

They were computers in their own right, however, with definite purpose operating systems and firmware.

Fast forward 40 years and we find ourselves in a situation where panel displays are so inexpensive with awesome software that every machine and process has visualization built-in.

I so remember when touchscreens were so clunky and expensive, but, as with all things technology, they are commonplace.

The early panel display had function keys along the bottom or the sides—different catalog numbers—for operator selections and the like. There was also a number pad for data entry. Data entry through software came a bit later.

And, as with everything else, the industry has consolidated into commodity items. Now instead of custom operating systems and firmware, which still exist, most run commercial operating systems such as Windows CE. Software replaces the firmware for application development, which brings us to the next step in HMI development.

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What makes a good HMI? The hardware it runs on is pretty much a commodity. It’s the software that makes the difference.

A high-performance HMI is now commonplace due to the hardware available to run the applications. Standard windows operating systems are available to be accessed on PC-based panel displays, such as Windows 7/10. This greatly expands the possibilities of HMIs with respect to communications, cloud-based applications, diagnostics and analytics.

The advent of PC-based HMIs allows for us to create extravagant displays in multi-color screens with animations and more information than we really need.

A good HMI design is still required regardless of what the hardware allows us to do. Well-balanced screens with moderate color changes and gradients are still required regardless of the horsepower of the display.

The new HMI designs can put function keys and selectors on screen since most HMI displays are now touchscreen.

Also coming on strong is the mobility of the displays—read smartphones. The HMI located on a machine can be replicated on your smartphone screen making your location redundant. You can be roving while staying in touch with your analytics and diagnostics.

While it is convenient, one wonders how much you can put in the screen real estate that the display offers that makes sense. Good HMI design again comes into play because of the screen size.

We tend to overdo the information on a screen, and unlike a mimic panel you may not have all of the information available to you based on the screen you are looking at. Process navigation and the two-to-three-click rule becomes uber important.

Panel displays have without argument allowed HMIs and in fact SCADA systems to become more prevalent in our industry for machine control, as well as an interface to any process. However with bad design the power of the display can be diminished regardless of the screen size, multi-touch displays and communication options.

Mycontrolroom.com has produced some reports and commentary on good HMI design and proper use of current HMI hardware platforms.

I have seen annunciator boards a mile long with multiple sets of eyes on different parts. Panel displays allow for a single set of eyes in a small spot. It is up to us to make the content usable and understandable. 

Let’s do the hardware proud.

ALSO READ: Visualize organization from chaos

About the author: Jeremy Pollard
About the Author

Jeremy Pollard | CET

Jeremy Pollard, CET, has been writing about technology and software issues for many years. Pollard has been involved in control system programming and training for more than 25 years.

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