HMI products originated as more complex machinery was developed, and a need for easier operation surfaced. Before HMI, products such as Batch Interface (1945–1968), Command Line Interface (1969–present day), and GUI (1981–present) were in use. While each interface had its own timeline, with some being used even today, HMI stemmed directly from GUI or Graphical User Interface.
A GUI makes use of buttons, text boxes, message boxes, lists, forms, etc. to provide the user with an interactable and easy-to-use interface. HMIs were developed on top of these to allow machines to be operated more effectively.
Human Machine Interfaces very widely, from control panels to nuclear facilities to mobile screens. But in this case particular, HMIs for manufacturing processes would be under discussion. For manufacturing lines, an HMI control panel offers centralized monitoring & control for the entire industry. A Programmable Logic Controller (PLC) is closely associated with an HMI as it serves as a backend control for every bit of information input/output from the HMI.
Decisions made in visual manner are far easier & comprehensible than those in command-based or manual environments. In order to provide total control to the user, the HMI must be in constant contact with the PLC, allowing it to serve real-time information. The HMI accesses specifics registers within the controller, and presents these to the user in an understandable manner. Similarly, when the user makes a decision, the HMI simply alters the values of the corresponding registers on the controller, eliciting a hardware-based reaction.
Before HMIs were introduced, they were mimicked by a hardware control panel that consisted of hundreds of LEDs & push-buttons to offer the user similar functionality. Today, the scenario is much different.
There are three basic types of HMIs:
The actual physical properties of an HMI vary from model to model, depending on the type of application and the manufacturer chosen for the job. An HMI located in a water plant would be characterized by several water-seals to protect it from malfunctioning. In retrospect, an HMI located in a warehouse wouldn’t require such features. The size of an HMI is dependent upon the specific application. If a complex function needs to be controlled then the system may require a number of large LCDs, whereas a meagre application may only require a small black & white monitor. In addition, the technical specifications also vary. For an HMI that must keep track & work with tons of parameters, high amount of memory & processing power is necessary, but for an HMI that only has to provide basic control, a significantly lower resource pool would be enough.
Considering the operating environment is an important step that shouldn’t be missed when selecting an HMI. For instance, an HMI installed in a warehouse may have to go through excessive vibrations. Similarly, an HMI installed in a food processing industry may have to deal with water, chemicals and other agents. For a steel plant, the temperature must always be considered as a selection factor.
There are three main categories of programming software to choose from for HMIs:
Proprietary software is provided by the manufacturer, and can be easily deployed without much hassle. The drawback of using this software is lack of support & flexibility for third-party hardware.
Hardware-independent software on the other hand is interoperable and supports a range of protocols, giving a great deal of freedom to the developer. But, it lacks the level of user-friendliness given by proprietary software.
Open software gives the developed total freedom in the design process, but should only be used by companies with dedicated R&D wings, as they require considerable amount of resources.
HMIs bring with them a number of benefits to the user and factor as a whole. These include:
PanelShop.com takes pride in delivering high quality custom control panels with concept-to-completion engineering support. Whether you know exactly what you need or you're seeking a partner to help develop and accelerate your project, PanelShop.com can help. Call us today or submit a quote, and find out how PanelShop.com offers the best price for the best quality.