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Industrial Automation



Device Type Definition

The software allows the user to define simple devices, which are associated with individual conveyor positions.

To define a device type, the user specifies, generically, the outputs, alarms, inputs, graphical representation of each state of an input of group of inputs, and then specifies and writes the program macros for the control and monitoring of the device.

Once a device type is defined, it can be replicated anywhere on the system via a single entry in the system specification, saying where it is in relation to a conveyor position.

These devices may range from simple devices, such as alignment bars, sizing stations, drop rollers, pallet stands, freezer or fire doors, floor loops, and zone control stations, to more complex devices, such as empty pallet dispensers, empty pallet stackers, and palletised load detierers.

For more complex devices still, such as depalletisers, basket loaders and unloaders, the PLC code is required to be hand-written and the status and alarms are presented on user-configured screens providing similar functions to those found in the popular SCADA packages.

Below is shown the device type definition screen (from the MS-DOS version of the “Movement Controller”):

Screen dump from DOS version of
Movement Controller, showing the
display which is used to define a device type for the heavy-unit-load conveyor
system, converted to a “gif” file, thereby losing some
of the colour definition

In the left window are listed the existing devices, with one selected (in this case the “Detierer”).

In the next window is the alarms, which lists all alarms for the selected device - it is rare for there to be more than one for most devices.

In the next window is the outputs, in the next the inputs (not shown - as you move across the windows, either the alarms or inputs window is sacrificed), which each list all outputs or inputs for the selected device.

In the last window are the conditions, where all conditions for the selected inputs are listed.

While in the devices window, information such as the name of the device and the names of the PLC program macros must be provided. You are later required to write the macros; this is the most demanding part of the configuration, but at least you are only writing the code once.

As you move across the windows, the content of the table changes allowing you to enter the corresponding data.

In each of the alarms, outputs, and inputs windows each needs to be named, given a two character code, and then provided with the generic part of the PLC comment, the generic portion of the alarm text, the text for the manual control push buttons, et cetera.

When you move across to the conditions window, the display will appear as below (from the MS-DOS version of the “Movement Controller”):

Screen dump from DOS version of
Movement Controller, showing the
display which is used to define a device type for the heavy-unit-load conveyor
system, this time with the “conditions” window active, converted to
a “gif” file, thereby losing some of the colour definition

Here we have chosen a different device, so as to illustrate the grouping of inputs. The selected input is “Stand is Up”, and the previous input, “Stand is Down”, is shown in grey, indicating that there have been no conditions defined for it.

As a result, the conditions corresponding to “Stand is Up” each contain two bits, one for each of these inputs. We have defined conditions where both are off (the stand is half way) and for when the stand is up. If the stand is down, nothing will be shown; and we should probably define a condition for the stand being both up and down.

When we select a condition, the display will appear as shown below (from the MS-DOS version of the “Movement Controller”):

Screen dump from DOS version of
Movement Controller, showing the
display which is used to define a device type for the heavy-unit-load conveyor
system, this time after selecting a condition to edit, converted to
a “gif” file, thereby losing some of the colour definition

The stand being up condition has been chosen (Down = 0 and Up = 1). The overview status is presented in a single colour and is defined using a pixel map. The zoomed status is constructed from lines, rectangles, circles, characters, et cetera, in a range of colours.

Colours can be selected by purpose or raw colour. Photocell lamps, for example, would be chosen by colour, so that when you get to site and the client insists that the photocell status be shown in black and white rather than grey and yellow, there is no great drama. Defining Heavy-Unit-Load Conveyor