How an HMI display can work in conjunction with stacklights

13 industry experts give ways that the combination can provide relevant performance or production information that helps to optimize production

By Mike Bacidore

How does an HMI display work in conjunction with stacklights to provide relevant performance or production information that helps to optimize production?

John CurtinJohn Curtin, director, automation solutions, Motion IndustriesWhile standard stacklights can provide visual status for a process, an HMI can be used in conjunction with the stacklights to offer versatility and an additional level of detail, which can help to reduce downtime and increase production optimization. There are myriad possible display configurations for the HMI. In a common format, an HMI can be programmed to display visual and/or text information to assist an operator with identification and location of a specific issue in the process, provide prompts for troubleshooting and include procedures to address faults. The HMI can also log system events, which can be reviewed to find patterns of system issues, leading to opportunities for process improvements.

Daniel Weiss thumbDanny Weiss, senior product manager, Newark element14: The HMI—for example, one that combines an operator interface with internal PLC capabilities including communication capability for Ethernet, Profibus and many others—can communicate to the stacklight providing more granular information. The operator or maintenance people can see detailed fault information from the HMI, as well as over a plantwide monitoring network.  Yet, many faults do not require detailed information; for example, when a sort area is jammed, a stacklight could easily indicate the problem without having to look at the HMI screen.

Tom RosenbergTom Rosenberg, vice president of marketing and engineering, Balluff: An HMI is a vital piece of the information puzzle. However, operators and other personnel cannot be staring at the HMIs all day. They have their main tasks to accomplish. So, stacklights and indicators are necessary at the point of use to inform personnel if there is information or input required back at the HMI. A communication plan is essential.


Lee Clore thumbLee Clore, owner/controls designer, Onyx Industries: Stacklights are the first line of defense, visible from longer distances than HMIs. When an event occurs, the indicator light is supposed to get the attention of the operator and allow them to make decisions; often, this leads to operators viewing process data on the HMI. HMIs are wonderful tools for seeing into the details of a machine.

They are not, however, readily viewable unless you are right in front of them. Well-placed stacklights are viewable all around the machine.

Alvaro SanchezAlvaro Sanchez, product manager, Rockwell Automation: In many instances, the HMI is used to display some production parameters and operation status of the machine/line that it is monitoring. However, the user needs to be relatively close to the HMI device to confirm that the machine is operating correctly or if it needs something to keep running. When a stacklight is paired with the HMI, important diagnostics or operation conditions can be displayed. The stacklight can alert users of any condition, even if they are not in front of the HMI, so the proper action can be taken on the machine. Basically, an HMI provides clear local indication and greater detail of machine status, but a stacklight communicates status over a wider area.

Todd Mason DarnellTodd Mason Darnell, Ph.D., marketing manager of services and safety, Omron Automation Americas: Perhaps the two ugliest words in the English language are “machine down.” Unfortunately, a stacklight only notifies plant personnel that there is a problem, without giving any guidance as to the nature of the problem, such as mechanical, safety or supply. Integrating an HMI can provide maintenance personnel with valuable information on the nature of the issue, enabling them to quickly recover the tool and resume production.

Vaidya Doc PatelVaidya “Doc” Patel, director, marketing & customer success, EZAutomation: An HMI can talk to various PLCs. In addition to that, it can display alarm messages, production count, machine uptime or downtime in the form of an alphanumeric message or graphs or meters, which are more visually pleasing, and easy to understand. In case of a machine down, HMI can be programmed to diagnose the issue and pinpoint the exact location of the issue. It can also be programmed to display the corrective action to get the machine up and running in an effective way. This not only reduces downtime, but also increases productivity.

Michael ONeill WermaMichael O'Neill, sales manager, Werma-USA: Stacklights have options to collect, transmit, store and display data of the critical parameters warranting a warning light when specifying a machine. Now the control of this data advances the stacklight from being more than a commodity of providing indication. The wireless transmission of the simple lighting of a stacklight can now notify people anywhere through the use of texts and e-mails to cell phones; display information for all to see on a shop floor via flat screens mounted in the production areas; store these parameters’ data for machine history; schedule and track production via pulses sent to the stacklight; and indicate failure of communication links.

Peter GaspariniPeter B. Gasparini, sales manager, Werma-USA: For Werma stacklights, we only need a signal, such as 24 Vdc, or 115 Vac, and then HMI displays are used in different ways. One way is to ascribe specific fault conditions to the light condition, such as permanent red LED on for 73 minutes. Why? Broken bit, drive, power outage. Clients use HMI display to select pre-loaded faults. 

Carter Williams, product manager, Siemens: Human-machine-interface (HMI) systems are designed to display feedback images of the user’s process task. When a stacklight is properly integrated into the HMI, it provides the operator with a visual indicator of the machine’s workflow, and it allows him/her to perform control functions to that process.

Lyon Lee 2Lyon Lee, product marketing manager, IDEC: HMI displays can be used to show details of the machine status or alarm code or to reset alarms. In addition, HMI displays can control the stacklight through direct wire connections.


White Paper: If stack lights could talk

Trey GanttTrey Gantt, product manager, EatonFundamentally, stacklights visually and acoustically amplify machine monitoring. As distractions in today’s facilities continue to increase, stacklights with the ability to demand immediate attention with innovative visual and audio functionality are crucial to keep personnel informed about machinery or processes. Industrial controls, including stacklights, need to support increased equipment availability through immediate notification. Versatile color options, lighting features, adjustable sound and alarms are important to keep personnel informed about material requirements, downtime and safety.

Steve Olson 1Steve Olson, IIoT technical specialist, Hilscher, member of Control System Integrators Association (CSIA): HMI display can act not only as a map for the location of the stacklights, but also as a mimic of the operation.


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