A Human machine Interface or Hmi is the graphical display that represents a machine, process, or installation so that the user can easily, intuitively operate and monitor the status of such a system.
A straightforward machine will want a straightforward interface for the user and not want a Hmi. A few indicator lights, some push buttons and switches will be all that is needed to operate a straightforward machine, say one that presses parts into a casting of some sorts. To quickly give you an idea of what the lights and push buttons would do, is to acquaint the operator that a part was in place and ready for the next step along the line to a terminated piece. The operator would know now the machine is ready, add other component to the part and push the appropriate button to begin the next action.
Way before there where the great color displays of today, a panel (metal, plastic or even wood) would be created and imprinted with a simplified version of the actual process. At key points on this panel, holes wold be drilled and indicators and pilot lights installed. This panel would be mounted on the wall and the panel for the switchgear such as push buttons and selector switches, mounted below. Typically placed at desk height to allow the operator to operate the machine or process.
Keep in mind that the Human machine Interface is just...well... An interface. What I mean is that the real operate and brain is handled by a controller, normally a Plc, although integrated Hmi/Plcs are available. The Hmi sends a ask for an performance by a graphic push button pressed by the operator to the controller. In turn an performance is performed though the brain programmed into the controller and the machine actual producing the action. The Plc straight through sensors placed on the machine can send this status to the Hmi.
The Hmi can be a self-contained touch screen gadget made specifically to be used with a singular brand of Plc or controller. While others are more universal and can be used with many controllers since they have most communication protocol included or communication drivers available. Usually, you will see these mounted right on the enclosure door of a operate cabinet. The Hmi is also the user's front end to a Scada system's controls and databases. Essentially Scada is the top level of operate of a network of Plcs controlling a large, involved process.
Other Hmis make use of a software holder and adapter for a coarse Pc. The adapter card is inserted into the Pc to enable association to a exact communication medium and protocol of the operate system. Depending on the provider and the power and complexity, the software holder will include a development principles and run-time license. In this way a developer can have one principles for creating the design of the Hmi and multiple less costly run-time licenses for use on every machine.
Good design is primary to collect the most benefit from a Human machine Interface. The Screens that are created, how they are laid out and how it all flows together can make a huge difference. Ordinarily a Main Screen, summary screen for each main area or system, a Current Alarms and Alarms History screen are a good start. The summary screen will provide passage to more detailed sub screens straight through a grouping of push buttons and/or logical drill down points on the summary screen. Easy navigation to and from related processes is primary as well as to the main screens.
Choosing the precise graphics from the included library and creating your own is foremost for depicting your machine or process so that operator will learn quickly and not become confused.
The included graphic libraries have cool looking indicators, push-buttons, meters, numerical displays, tanks, piping, valves, motors, blowers, etc.
Creating a great Hmi is part art, part engineering, part psychology. A appropriate insight of the process is primary and it can be quite a bit fun, especially for the creative types among us.
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