Setup of Digital Input in Accord Builder
A Digital Input State is an indication that a physical On/Off, True/False type state has been achieved.
Digital Inputs are items such as Level Switches, Proximity Switches, signals from other PLC’s, buttons and other inputs that do not have a corresponding digital output.
Following insertion in a unit, a digital input is configured with settings that will determine its operation and its description in documentation. During insertion, the input is given a name and short description. The name may be changed at any time.
There are three tabs in the digital input properties configuration section. The name and units of the digital input are given in the Current Item section. Cross reference, Save and Close buttons are also provided.
The following aspects of the device must be filled as required:
Address: This is the PLC input address for the device.
Delay On SP: This is the de-bounce time, in seconds, for which the digital input must be electrically present before it is recorded as being ON.
Delay Off SP: This is the time, in seconds, for which the digital input must be not electrically present before it is recorded as being OFF.
Normally Open / Normally Closed: A digital input is normally recognized as being ON when the electrical signal to the PLC input point is present. By selecting the Normally Closed Input, the user can declare that the input will be ON when the electrical signal is present. A common example of this is a Vessel Low Level Signal where (for failsafe reasons) the true low level (tank empty) is recognized when the signal is present.
State Text: This text is used to describe the On and Off states of the item in the HMI controls. This is a free text field.
Indicate Only: Digital Inputs by usually referenced in Programs. This option is used if the item is only required to be monitored.
Generate Alarm: This is used to put cause an On state to cause a HMI Alarm. The Short Description will appear in the Alarm Control.
Place Unit in Alarm: This is used to put cause an On state to cause a Program Alarm.
Card Setup Tab:
A PLC is composed of a CPU and I/O cards on racks, and in some cases communications processors, special function modules and bus based I/O.
Panel, Central Rack, Slot and Channel: These are all text input fields. Once a text is entered for a device or instrument, it then becomes available for other objects in the project. There is no validation on this information; the same combination of information could be entered for more than one device. This would be erroneous as each device must be unique, so care must be exercised in inputting the information. This can be filled in the IO Table in the Menu.
Type: This is the type of electrical signal associated with the Digital Input. In this case a 24v DC signal is identified. The information stored in this area is used for documentation and does not comprise object data for PLC control.
The following aspects of the device may be filled in if required:
Symbol: This may be an asset number or any unique identifier which describes the object within the entire company. This could contain references to the plant, the area within the plant, the unit and the digital input name itself.
Part Number: This is the supplier reference for the item.
Type Description: This is a general description of the type of item. If a type is entered, then it becomes available to all other objects of the same type.
Long Description: This describes the object in more detail, if required.
Supplied By: Name of the supplier.
Notes: General Notes on the object. This may contain reference to maintenance manuals, maintenance history or location and type of spare parts.