Example: Ignition Input Handling - Shutting Down the Display

Ignition Input Functional Overview

OpenView Codesys Displays have two SYSTEM variables associated with the Ignition Input allowing you to monitor the state of the ignition input and to perform a controlled shutdown on loss of the ignition signal. 

To power up the display both Vbatt and Ignition need to have battery power applied. Once powered up the power supply will be held active even if the ignition input is removed. This allows the developer to programmatically monitor the state of the ignition input signal and choose to take any actions needed. The display can be held on indefinitely until Vbatt is removed or a command can be sent to shut the display down immediately or after a time delay. 

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System_Ignition_Pin Variable

• Physical state of the Ignition Pin on the display. Used to determine if the unit is allowed to shut down. 
• 12V applied to the ignition Pin = TRUE, nothing applied to ignition pin = FALSE

System_Ignition_Shutdown Variable

• Command to shutdown the display.  
  To shut down the display, the System_Ignition_Pin must be false, and the System_Ignition_Shutdown variable must be true. 

Basic Logic Flow

The basic logic flow to shut the display off on loss of Ignition Input is as follows:

IF System_Ignition_Pin = FALSE THEN
System_Ignition_Shutdown = TRUE
END_IF 
This results in an immediate shutdown of the display. Alternatively, a user can define tasks or timers to run before shutdown so the shutdown is not immediate. 
IF System_Ignition_Pin = FALSE THEN
DO STUFF
IF STUFF = DONE THEN
System_Ignition_Shutdown = TRUE
END_IF
END_IF