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Detecting Beacon Signal Status, Productivity 2000 PLC

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  • Detecting Beacon Signal Status, Productivity 2000 PLC

    I am using the beacon signal on a HAAS CNC lathe to communicate machine status to the PLC for robot integration. If the beaconis steady on, the machine is running a program. If the beacon is off, the the machine is in reset mode, and the tricky one is if the beacon is flashing, the machine has received a M30 command indicating the program is complete. This is my signal that the robot can do its thing. As you can tell, I am not an expert at programming PLC's. How can i most efficiently detect these three states. The flashing beacon operates at a frequency of 1Hz with a 75% duty cycle. On .75 sec and off .25 sec. Thank you for your help.

  • #2
    two timers looking at the beacon signal.
    one looking at NO, one looking at NC
    each timer preset should be just a bit longer than the prescribed duration - you can modify these to suit your situation
    If either timer expires, the signal is steady
    if the timer looking at the NO times out, the signal is high - steady
    if the timer looking at the NC times out, the signal is low - steady

    if BOTH timers keep getting reset, the signal is flashing


    • #3
      Thanks, kewakl. I'll give this a try and let you know how it goes. I appreciate your help.


      • #4
        Thank you again. That worked perfectly


        • #5
          Thanks for the update.


          • #6
            While the code from Kewakl works well, I would add to it a way to clearly know for sure the flashing is happening.
            After the above code is written for the timers I would make a line below it for a simple counter set at a count of 3. The input for the counter is your beacon signal contact, reset is the done bit from the on timer. This will keep the counter reset and holding at 0 if the beacon signal stays steady on, but will count if the signal is flashing. If you reach a count of 3 then you know for sure the signal is flashing. This could probably be lowered to a count of 2 to shave a second off the detection time, but you could start at 3 for initial config and confirmation of functionality.

            Up to you whether you need to implement this functionality or not. With PLCs the nice thing is that there is no wrong way to do something as long as it works reliably for the application you are trying to do.