Watlow EZwarePlus Programming - Manual (Page 11)

EZwarePlus Programming Manual 3
OIT/HMI Basics
Operator Interface Terminals (OITs) and Human Machine Interfaces (HMIs) provide much more versatility than
traditional mechanical control panels. An OIT allows a plant floor operator to monitor current conditions of a control
system and, if necessary, to initiate a change in the operation of the system. OITs connect to programmable logic
controllers (PLCs) typically through the PLC’s serial communications port. The OIT can be programmed to monitor and
change current values stored in the data memory of the PLC.
OITs can have either text-based or graphics-based displays. A text-based OIT can display text characters but no
graphics. Some text-based OITs can display text characters in various sizes. A graphics-based OIT can display text
characters of varying fonts and sizes and graphics shapes such as icons, bitmaps, or pictures. Using pictures instead of
words or characters often greatly simplifies the operation of the OIT, making the OIT much more intuitive to use.
Some OITs use touchscreen displays while others use a membrane-style keypad. Membrane-style keypads are best
used in applications in which the keypad is likely to become dirty. Touchscreen displays are placed over the OIT
screen thus providing much more flexibility than typical membrane-style keypads. Because of this, switches can be
created on a touchscreen that appear only when needed.
The Maple Systems HMI5000 Series are graphics-based touchscreen OITs. The terms OIT and HMI can be used
interchangeably, so we will use HMI in most cases. Now let us define some terms that are used throughout the
EZwarePlus Help files.
Projects
The HMI has two basic segments of internal memory. The code memory contains the information required by the HMI
that controls how it operates such as the features supported and how it communicates to a PLC. The HMI
programmer does not have the ability to change code memory. The project memory pertains to all the window
screens created and any other features that the HMI programmer can create using the EZwarePlus configuration
software. Therefore, the term project is used to designate the file that is sent to the HMI from the EZwarePlus
software.
Backing Up Projects
We recommend that you frequently back up your projects to another folder or an
external or network drive. In addition, when you have completed a project,
archive it by running the compression utility (Tools > Compress/Uncompress),
which bundles the project with the libraries that are associated with the project.
This allows the project to be opened on another computer and retain all the
shapes and pictures that are linked to the project. Refer to the Help menu for
more information (Help > Help Topics > Contents > How Do I…Backup a Project?).
Objects
An object is any ‘thing’ that performs an action while the HMI is communicating to the PLC. In order to get the HMI to
‘do anything’, you must program the HMI with objects. Objects perform actions such as display text or graphics, write
a value to a PLC register, or display an alarm. Objects most often are graphics shapes that are to be displayed on the
HMI screen. For example, a Text Object is used to display text on the HMI. But objects are also used to configure the
HMI to perform some action. For example, a PLC Control Object tells the HMI to continuously monitor a PLC register
that is used by the PLC to request a new window. Some objects can display a graphics shape on the HMI screen and
perform some action. For example, a Toggle Switch Object creates a graphic object on the HMI that, when pressed,
activates a bit in the PLC.
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