Structured Text repeating timer based on true/false bit

spatricks · Jan 14, 2013

How would I make a timer that would repeat on an interval as long as a certain value is true.

IF EVENT THEN
EVENTXBIT := TRUE
ENDIF

IF EVENTXBIT = TRUE THEN
DO THIS
WAIT X MINUTES
END_IF

IF ANOTHER EVENT THEN
EVENTXBIT := FALSE
ENDIF

This is what I have so far. It counts up to 3 min and then stops, instead of resetting. I figured since I change the variable to false it should retrigger.

Code:

TEST_VAR := TRUE;
TIMER_RETRIGGER_ALM0(TEST_VAR,T#3m);

IF TIMER_RETRIGGER_ALM0.Q THEN
	TEST_VAR  := FALSE;
END_IF;

KalleOlsen · Jan 15, 2013

TEST_VAR := TRUE;
TIMER_RETRIGGER_ALM0(TEST_VAR,T#3m);
IF TIMER_RETRIGGER_ALM0.Q THEN TEST_VAR := FALSE;
TIMER_RETRIGGER_ALM0(TEST_VAR,T#3m);
END_IF;

The timer is always called with a TRUE signal and does not 'know' the signal shift.
Try to add the cursive line and see if that works.
The output (.Q) will likely reset also, so you will not be able to catch it outside this code without copying it to another variable.

Kalle

ndzied1 · Jan 15, 2013

This is how I would do it. Note that this is CoDeSys and it looks like the timer call is a little different than what you are using.

To have something to do each time the timer times out, I just incremented a variable. The thing you want to happen at each timeout should go in the IF/THEN block where I'm incrementing the i variable.

I don't like calling the timer in multiple places as if they get spread out, it can be very difficult to troubleshoot.

Code:

PROGRAM PLC_PRG
VAR
    I: INT;
    FirstPassDone: BOOL;
    Timer_Retrigger_ALM0: TON;
    TEST_VAR: BOOL;
    ALM0_Trigger: BOOL;
END_VAR

(* Run Code on First Pass through Program *)
IF NOT(FirstPassDone) THEN
    I:=0;
    FirstPassDone := TRUE;
END_IF

(* Call the Timer *)
Timer_Retrigger_ALM0(IN:= ALM0_Trigger , PT:= T#5s);

(* Set the Timer Trigger *)
ALM0_Trigger := (TEST_VAR AND NOT(Timer_Retrigger_ALM0.Q));

(* Do Something each time the timer finishes *)    
IF Timer_Retrigger_ALM0.Q THEN
    i := i + 1;
END_IF

spatricks · Jan 15, 2013

This is what I figured out before seeing your responses. Let me know what you think. Basically if the ACK bit is the conditional variable.

Code:

TIMER_RETRIGGER_ALM0(NOT TIMER_RETRIGGER_ALM0.Q AND ALM0_ACK,T#2m);


IF TIMER_RETRIGGER_ALM0.Q = TRUE THEN
	 DATA_inputONOFFSMSText := '';
   	 DATA_inputONOFFSMSText := 'Alarm detected: Input 1 is ON';	
  	 UTIL_SEND_SMS_2( TRUE, CONFIG_slotID, CONFIG_receiverList, DATA_inputONOFFSMSText);
	 
END_IF;

shooter · Jan 15, 2013

TEST_VAR := TRUE; TIMER_RETRIGGER_ALM0(TEST_VAR,T#3m); (* after 3m Q will be high always. IF TIMER_RETRIGGER_ALM0.Q THEN TEST_VAR := FALSE; END_IF;
In codesys you can not wait (all plc cant)
but you can use an AND if timer not expired and input true then do your thing.

Structured Text repeating timer based on true/false bit

spatricks

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ndzied1

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shooter

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