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How to create a stopwatch?

Engineering 🇬🇧
open
2023-12-07
2023-12-16

  • open - 2023-12-07

    Hi,

    how to create a stopwatch when start is pressed, timer will start counting and stop is pressed, timer will stop counting in structured text?

     

  • ph0010421 - 2023-12-07 
    FUNCTION_BLOCK fbdStopwatch
VAR_INPUT
    Condition: BOOL;
END_VAR
VAR_OUTPUT
    TimeTaken: TIME;
END_VAR
VAR
    StartTime: TIME;
    fbiStartOs: R_TRIG;
    fbiStopOs: F_TRIG;
END_VAR

    and then:

    fbiStartOs(CLK := Condition);
fbiStopOs(CLK := Condition);

IF fbiStartOs.Q THEN StartTime := TIME(); END_IF;
IF fbiStopOs.Q THEN TimeTaken := TIME() - StartTime; END_IF;
     

  • open - 2023-12-08

    Hi @ph0010421,

    I tried the program the TimeTaken is calculated when stop is triggered. I want the TimeTaken to be continuously calculated and counting when a BOOL variable is true.

    I tried to program this way:
    Declaration:

    PROGRAM PLC_PRG
VAR
    bStartStop: BOOL := FALSE;    // Start/Stop button
    bReset: BOOL := FALSE;        // Reset button
    bRunning: BOOL := FALSE;      // Flag indicating whether the stopwatch is running
    tStartTime: TIME;             // Variable to store the start time
    tElapsedTime: TIME;           // Variable to store the elapsed time
END_VAR

    Implementation:

    // Main program logic
IF bReset THEN
    // Reset button pressed, reset the stopwatch
    bRunning := FALSE;
    tElapsedTime := T#0s;
ELSIF bStartStop THEN
    // Start/Stop button pressed, toggle the running state
    IF bRunning THEN
        // Stop the stopwatch
        bRunning := FALSE;
    ELSE
        // Start the stopwatch
        bRunning := TRUE;
        tStartTime := tElapsedTime;
    END_IF;
END_IF

// Update the elapsed time when the stopwatch is running
IF bRunning THEN
    tElapsedTime := tElapsedTime + T#1s; // Adjust the time increment as needed
END_IF

    However counting of the seconds is not accurate. I tried changing the main task cycle time interval to 1000ms. The counting of seconds become slower. (see attached)

    Please help

     
    Thumbnail
    2023-12-08_09h44_42.png

  • ph0010421 - 2023-12-08

    Do you need an 'hours-run' counter? And 1 second resolution is ok? I think you're over-thinking it.
    (The task time needs to be < 1second)

    Have a look at the LAD...
    Then, the time in seconds can be made into hh:mm:ss with this FUNction
    Declarations:

    FUNCTION funSecondsToStringTime: string 
VAR_INPUT
    InSeconds: UDINT;
END_VAR
VAR
    AsString: STRING;
    Minutes: UDINT;
    Hours: UDINT;
    Seconds: UDINT;
    MinutesAsString: STRING(2);
    HoursAsString: STRING(2);
    SecondsAsString: STRING(2);
END_VAR

    and the code:

    Hours := InSeconds / 60 / 60;                               //Derive hours
Minutes := (InSeconds - (Hours * 60 * 60)) / 60;            //Derive minutes
Seconds := InSeconds - ((Hours * 60 * 60) + (Minutes * 60));//Derive seconds
HoursAsString := UDINT_TO_STRING(Hours);
MinutesAsString := UDINT_TO_STRING(Minutes);
SecondsAsString := UDINT_TO_STRING(Seconds);

IF LEN(HoursAsString) = 1 THEN
    HoursAsString := CONCAT('0',HoursAsString);
END_IF;

IF LEN(MinutesAsString) = 1 THEN
    MinutesAsString := CONCAT('0',MinutesAsString);
END_IF;

IF LEN(SecondsAsString) = 1 THEN
    SecondsAsString := CONCAT('0',SecondsAsString);
END_IF;

AsString := CONCAT(HoursAsString, ':');         //assemble string
AsString := CONCAT(AsString,MinutesAsString);
AsString := CONCAT(AsString,':');
AsString := CONCAT(AsString, SecondsAsString);

funSecondsToStringTime := AsString;
     
    Thumbnail
    RunCounter.png

  • Ton - 2023-12-09

    One i wrote this to measure elepse time

    When xMeasure is true is starts en when false it stops and time is messured.

    FUNCTION_BLOCK FB_ElapseTime
VAR_INPUT
    xMeasure: BOOL;
END_VAR
VAR_OUTPUT
    xRisingEdge: BOOL;
    xFallingEdge: BOOL;

    tElapsed: TIME;
    ltElapsed: LTIME;
    ltPrev_Elapsed: LTIME;
    ltElapsedMax: LTIME;
END_VAR
VAR
    xLastValue: BOOL;

    LTIMEStart: LTIME;
    LTIMEEnd: LTIME;
    tonReset: TON:= (IN:= TRUE, PT:= TIME#30S0MS);
END_VAR
-------------------------------------------
xRisingEdge:= (xLastValue XOR xMeasure) AND xMeasure;
xFallingEdge:= (xLastValue XOR xMeasure) AND NOT xMeasure;
IF xRisingEdge THEN
    ltPrev_Elapsed:= ltElapsed;
    LTIMEStart:= LTIME();
END_IF
IF xMeasure OR xFallingEdge THEN
    LTIMEEnd:= LTIME(); 
END_IF

ltElapsed:= LTIMEEnd - LTIMEStart;
ltElapsedMax:= MAX(ltElapsedMax, ltElapsed);
tElapsed:= LTIME_TO_TIME(ltElapsed);

xLastValue:= xMeasure;

tonReset();
IF tonReset.Q THEN
    tonReset.IN:= FALSE;
    ltElapsedMax:= LTIME#0NS;
END_IF

    Meaby this will help.

     

  • open - 2023-12-11

    Hi @ph0010421 and @Ton,

    Is it possible to program a stopwatch to measure a system running time when it is turn on, and pause when the system is turn off. I tried your examples when stopped, the elapsed time will then be calculated, but i need the time to be continuously counting.

    Warmest regards,

     

  • Ton - 2023-12-12

    Hi,

    i guess you want to make a hour counter.

    You need to store the measured value.
    Try to use a retain variable, but need a graceful shutdown, or save it your self.
    see https://forge.codesys.com/forge/talk/Runtime/thread/278e325579/

    Succes.

     

  • open - 2023-12-14

    Thanks everyone for your input,

    I am using persistent variables to retain the timer value after machine shutdown, and main task to be as low as possible for the seconds TON to be accurate.

     

  • Ton - 2023-12-16

    If you use LTIME() you will be very accurate and be able to have a normal task cycle time.

     

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