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July 28, 2020

Considering the options: Pushbutton vs HMI display controls

by Gary Roberts, Automation, Northwind, USA

Those of us that are familiar with controls systems have seen some of the benefits that can be gained when using a human machine interface (HMI) versus using a simple pushbutton control panel.

Some of the main benefits an HMI provides include increased efficiency, safety, and overall functionality. While a pushbutton panel is easily understood and simple, it can be severely limiting in the level of complexity the systems it can handle. Another limitation is that the efficiency of a pushbutton panel depends solely on the experience of the operator.
 


Pushbutton control panels
Plants have been running for ages using pushbutton equipment control. This method is well understood by the people who operate these systems and their efficiency is directly tied to the experience, proficiency and focus of the operator. Because pushbuttons are simple, it is sometimes an inexpensive solution for use in small systems. Ideally, a pushbutton panel is used on a simple system with just a few pieces of equipment. For example, it may be easier to understand and functionally adequate to run a small vacuum and receiver system by simply using a “start/stop” button.

Pushbutton panels begin to exhibit shortcomings when the system grows to more than just a few pieces of equipment. With multiple machines in operation, it is not always clear which machine is running at any given time and this can make diagnosing issues a nightmare. Another shortcoming of pushbutton panels is that it is hard for new workers to learn how different operating systems interact with others on the plant floor.

This can lead to increased training time and lower production as a trainee is learning to use the system. Further limitations of pushbutton panels come in the area of documentation. Because there is no display available on the panel, it is often necessary to go to each piece of equipment in the plant to document weights, flow rates, etc. Also, in order to troubleshoot a pushbutton panel, the panel door must be opened. This can lead to safety hazards with live voltage or difficulties troubleshooting if the panel is powered off.


Read more HERE.
 

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