Ladder program to start robot in EXT mode

  • Hello,

    In the following image is the ladder block I'm using to start a robot in EXT mode from a siemens PLC. This block was made based on the signal diagrams on the KSS manuals but it seems to not work sometimes. 95% of the time when this block is run the robot starts correctly but sometimes it doesn't respond, as if the start sequence wasn't received.

    Just to clarify, "RobotControl" in this example is a structure to write commands and the status of the robot.

    I was wondering if any of you could share how you do it or at least any comments or opinions.

    Thank you.

  • I'm pretty sure that's wrong. CONF_MESS should be used before DRIVES_ON, and should not be dependent on PERI_RDY. There are conditions where it's not possible to get the drives to engage until after CONF_MESS has been pulsed to clear STOPMESS.

    CONF_MESS should also be a pulse -- as written, your logic will hold it TRUE under certain circumstances, and the robot only responds to a rising edge (DRIVE_ON and EXT_START behave the same way).

    Aside from that, it looks pretty decent overall. The use of feedback signals instead of timers to generate most of the pulses is clever, and should avoid any issues of sending signals too close together.

  • Hello Skyefire,

    According to the signal diagrams $DRIVES_ON precedes $CONF_MESS. The dependence between $PERI_READY and $CONF_MESS is simply to have the sequence run without any timers.

    Would you say it's safer to just make it based on timers and make sure enough time passes between signals?

  • the issue here is lack of understanding of signal types. Some are level sensitive while some edge sensitive. When edge sensitive input misses transition, it does nothing...

    Signal types are clearly documented and visible in timing diagrams.

    A while ago i shared ladder logic example for this. that example is rock solid.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

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