mdjames (Customer) asked a question.

Edited February 11, 2021 at 10:19 PM
Parallel Timers

Hi There-

 

This is my first ladder logic program so I was hoping to get some experienced eyes on it to see if I'm on the right track, or if I'm missing something.

 

What I'm essentially aiming for is to monitor two analog sensors, and activate output pins based when those sensors exceed a threshold for a certain amount of time.

 

More specifically, the sensors are current sensors. When either current sensor exceeds a set value (270A in this case) for 5 continuous seconds, it should trigger Y001. When either current sensor exceeds the set value for 15 continuous seconds, it should trigger Y002.

 

I'm mostly concerned I might be missing an interaction between the timers. Will they operate independently and in parallel?

 

Below is a screenshot of my logic. DF1 is the value of current sensor 1, DF2 is the value of current sensor 2.

 

Edit: I'm planning on using a single Click analog PLC.

 

Thanks!

 

Capture

  • 5 answers
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  • Garry (Customer)

    Your code looks good. The timers act independently.

    The only thing that I see is if DF1 exceeds the threshold and after 3 seconds, DF2 exceeds the threshold the timer keeps timing. After 4 seconds DF1 is below but DF2 is still there to make the timer expire and turn on the output. Your program is a combination of both DF1 and DF2.

    If this is not desirable, then just use separate timers for each condition and parallel the contacts on the output.

    Regards,

    Garry

     

    https://accautomation.ca/series/click-plc/

     

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  • Garry (Customer)

    Your code looks good. The timers act independently.

    The only thing that I see is if DF1 exceeds the threshold and after 3 seconds, DF2 exceeds the threshold the timer keeps timing. After 4 seconds DF1 is below but DF2 is still there to make the timer expire and turn on the output. Your program is a combination of both DF1 and DF2.

    If this is not desirable, then just use separate timers for each condition and parallel the contacts on the output.

    Regards,

    Garry

     

    https://accautomation.ca/series/click-plc/

     

    Expand Post
    Selected as Best

  • mdjames (Customer)

    Thanks! Great observation about the DF1 and 2 interaction, I'll give that some thought.

  • bcarlton (Customer)

    Another answer but only using 2 timers is to route the DF1 and DF2 conditions to their own timer with 15 seconds as a setpoint. For the Y1 output parallel two comparisons of each timer's Current >= 5. The Y2 output would be the parallel of the timer's Done bits.

    • mdjames (Customer)

      Interesting take. Is there a benefit to using fewer timers?

      • bcarlton (Customer)

        In the early days of PLCs it might have been a consideration but not so much now. It's more a consideration of the programmer's personal style and understandibility especially to some future tech who may be using it. Naturally good comments help.

 

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