Human-machine interfaces redefine SCADA and cloud integration

By now, everyone knows how and what human-machine interface (HMI) systems do for automated processes. And they do it admirably.

There have been arguments on how to do screen design, color selections, piping and instrumentation diagram (P&ID) replications and, of course, alarming and data logging, among other things.

With the advent of common connectivity standards such as Ethernet/IP, Modbus/TCP and EtherCAT, to name a few, HMIs can talk to just about anything.

Open platform communications (OPC) has had a lot to do with that, as well. Some controllers have an OPC server built in, so OPC clients can extract data from them. Native system drivers are still valid, however, and in fact may have better response times.

Part of the current crop of HMIs boast about living on the edge. Message queuing telemetry transport (MQTT) protocols live there, as well. The cloud also comes into play where the HMI will scale and format data from the control strategy and pass that up to the cloud for data integration into various systems. This was normally the job for the supervisory control and data acquisition (SCADA) system as such, but it has dropped down a level or two to the process interface.

Back when HMIs were hardware-based, the resulting interfaces and response times were acceptable. They connected to programmable logic controllers (PLCs) using built-in drivers on proprietary networks. They were expensive and did the job, but only the job at hand. There was no additional software resident in the system to do much with data. There was no local persistent data—just real-time information on a screen.

When the IBM PC came out in 1981, industrial computers started to become available, and DOS-based HMIs became available but were still very expensive. Local data storage became available due to the fact that the HMI now had a hard drive. SCADA systems became prevalent, which blurred the lines between HMI and SCADA in functionality and connectivity. SCADA doubled as an HMI and a data concentrator, among other things.

You could install communication cards for communication to the corporate IT network and to control OT system networks, and the software would bridge between the two. Technology was changing the landscape of graphic interfaces.

Software got better. Windows-based systems became the norm in the 1990s, which provided the developer the ability to create control interfaces with more widgets and icons, with multiple drivers allowing for an HMI to aggregate data from different network protocols. The big leagues had arrived, which leads us to system of today—the controller and the HMI are integrated together on one platform.

Micro-controllers for the smallest of applications can have an HMI built in; just add a monitor and keyboard. The cost is minimal, giving the control community the ability to create low-cost control and HMI solutions for just about any controllable system.

Vending machines surprisingly can have a compact PLC with a touchscreen interface for the control of product distribution. One of the most interesting applications of this strategy was a real-time French fry machine. It’s a process with analog and digital machine control.

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Moons ago, the cost and control system abilities would not have allowed for this development. I wonder when the industry of on-demand food preparation involves robot-created delights in an airport waiting room. The technology is there to do it.

Pizza creation has advanced to have robot involvement in forming and baking the pies. It would not be a big stretch to make the system portable.

Medium-sized systems need a robust HMI system to access and control the process. The capabilities of the small HMI may be able to deal with the needs of the design, but I would suggest that a full HMI system based on an expandable hardware platform would have the ability to add functionality as you go. Part of the mindset would be for expansion and add-ons such as multiple ethernet cards.

Ethernet and all its protocols have changed the game, allowing HMIs to connect and communicate to almost anything. Integration of disparate systems becomes a task of ease. A built-in HMI system may support multiple protocols, but, if it doesn’t, you may not be able to install that add-on later.

The system design needs to take into account what the future may hold and what devices may be connected to the existing HMI system. One of the most common desires is data in the cloud.

HMI can also be SCADA. Its personality depends on what you design into it. And don’t forget security.