Timer Doubt - Measure working time

Hello,

Sorry for this question (which certainly should be easy) but I'm new in PLC programming and in Step/Siemens.

I intend to monitor the duration, in seconds, of the operation of a pump. For this, I use the RD_SYS_T function (and convert to TIME_of_Day) when I trigger the pump through a boolean input (button from the HMI). Then I use another button (boolean input) to another RD_SYS_T function, and then I use T_DIFF to subtract these two (and convert to TIME and divide by 1000 and 60 to get minutes and seconds).

However, this is not working (T_DIFF always giving 0) and after placing the several variables in the HMI to see them, I saw that theses functions were getting new values each time the program cycle was executed again and the inputs (buttons) were ON.

Is there any way to get the output of the RD_SYS_T only one time (just one value), when the input (HMI button) change from 0 (off) to 1 (on)?

Again sorry for this question... Thank you for the help

These posts should help you:
[LINK1]
[LINK2]

Hi ,

After reading the links that you suggested before some doubts appeared. The RM instruction is not just for hours? I did not understand if the instruction gives minutes and seconds, because what I need is to show in a HMI the minutes and seconds that a given process has taken, and after reset the timer (or something else) for the next time the process is made.

Thank you for the help 

..okay.

Maybe you should have a look at the IEC timers.
The TONR instruction will be of most use to you.

Hi ,

That is probably what I need! I will try it and see if results.

Thanks for the help :)

Hi,

It was really the TONR I needed. Thank you!

However, I now have another doubt. Could you possibly help me?

Now I can count the time that the process takes, and can pass it to another variable (and show it on the HMI that I have). However, when I click on a button that I have on the HMI (boolean - to reset the timer), it resets the timer but also the variable that I used (because in the next execution of the program cycle, when I reset the timer, the 0 value passes also to the other variable that I use to show in the HMI).

Is it possible to prevent this from happening?

Thank you for all the help 

bruno_cardoso

Hi,

It was really the TONR I needed. Thank you!

However, I now have another doubt. Could you possibly help me?

Now I can count the time that the process takes, and can pass it to another variable (and show it on the HMI that I have). However, when I click on a button that I have on the HMI (boolean - to reset the timer), it resets the timer but also the variable that I used (because in the next execution of the program cycle, when I reset the timer, the 0 value passes also to the other variable that I use to show in the HMI).

Is it possible to prevent this from happening?

Thank you for all the help 

It would be of much help if you showed a screen capture of the piece code that does the reset / carry over time value to HMI / value on HMI.

If you do not want the HMI value to become zero when you press the "reset" on the HMI, then I would suggest that you create a PLC "event" that copies the timer's value to the HMI variable.

In other words.. when do you want the HMI value to be the same as the timer's value?

I would image you displaying
a) the actual time value right at this moment
b) captured time value (capture buffer)

So the following sequence might then occur..
- user push "reset" button
- timer value >> capture buffer
- reset timer

If you supply more info.. then the help can be more detailed.

w

Hello,

Sorry for the delay to answer but I've been trying to solve a problem with a flowrate sensor that was not working properly with the PLC .

The printscreen with the piece of code is in the attachment.

My problem is that when I click on the HMI button (M0.4 - "Finalizar") it resets the timer variable, however as it continues with the value "ON" (1), it ends up passing this value (which has been reseted) to the HMI variable. What should I do?

Thanks for the help

bruno_cardoso

Hello,

Sorry for the delay to answer but I've been trying to solve a problem with a flowrate sensor that was not working properly with the PLC .

The printscreen with the piece of code is in the attachment.

My problem is that when I click on the HMI button (M0.4 - "Finalizar") it resets the timer variable, however as it continues with the value "ON" (1), it ends up passing this value (which has been reseted) to the HMI variable. What should I do?

Thanks for the help

Hi.

Please consider using another M-bit for your HMI and use that M-bit only on functions you wish to have that M-bit have an influence.

Also..
On the HMI - you will probably use a "set" function (action). Have the PLC reset the M-bit as soon as all the actions are done. Example:
1. HMI: SET M1000.0
2. PLC: M1000.0 = ON do MOVE 0 into #VALUE
3. PLC: RESET M1000.0

I hope I understood your question.
Feel welcome to return with your thoughts.

w

Hi ,

Sorry but I did not understand what you meant by "Please consider using another M-bit for your HMI and use that M-bit only on functions you wish to have that M-bit have an influence.". Would you mind explaining?

I do not know the function "Set". Where can I read about it?

By the way, if the M1000.o remains "on" as suggested it will not end, in the next PLC execution cycle, by resetting the variable, and this ending up being sent to the HMI (thus appearing in the HMI is set to 0 as time process)?

I did not understand "2. PLC: M1000.0 = ON MOVE 0 into #VALUE".Should I pass the value "0" for which value?

Thanks in advance