KRC2 I/O Module Question

  • Hey there Kuka community,

    I have a question which, I believe, will be easy for you all to answer. Our immediate project requires the control of a 5.5vdc/5.0a closed loop 2 phase stepper motor. It is currently connected to a provided 110vac driver. My question is, should I use a DeviceNet I/O module to send a +/- pulse signal to control speed and a +/- direction signal to the 110vac driver or should I kill the provided driver and use a Wago I/O style stepper controller like the 750-672?

    System Details:

    -KR200-3 with a KRC2

    -integrated VFD run spindle through a DeviceNet Wago 750-306

    -external rotary axis

    -unused/free I/O modules 750-402, 750-504, 750-600end


    1. Control stepper with Wago I/O Stepper Controller Module or provide 110vac to original stepper driver and use some other module to send +/- pulse signal and +/- direction signal?

    2. Which I/O module should I use for the latter option?

    3. Is it even possible to provide 110vac to externals through the KRC2?

    I know this is a worn out topic, however, I see little information regrading I/O hardware choices. Thank you all for any and all advice and recommendations. I am also happy to share any other info to aid in the decision making.

    -attached is a sketch of the project thus far


    Matt Corbitt

  • Nation

    Approved the thread.
  • so your current idea as to use pulse and direction but did you do any sanity checks?

    KRC interpolation cycle is 12ms. so in one second you can toggle output some 83 times. assuming your code is very efficient that would allow you to generate pulse train of 41.5Hz.

    to do positioning you would need PTO that runs at some 100kHz or better which is off by just three orders of magnitude. but it could work if you can live with 2000-5000x lower performance than usual and know how to use KRL to its fullest.

    the solution is to insert intermediate node acting as controller/indexer. KRC should only send values and let the external controller do the time critical tasks, closed loop etc. IO connected to KRC are meant to be just conventional digital inputs and outputs. any time you add module with more complexity you are asking for trouble and basically you are on your own, wandering into uncharted territory.

    750-672 should solve this if you can get it to work with KRC. in theory that should work as the interface seem to be just two simple blocks of inputs and outputs of 11 bytes each. but getting to talk over DeviceNet to KRC is only the first hurdle. next one is to translate CoDeSys library into KRL, perhaps only the functions you really need.

    robot arm is irrelevant for this topic of integrating controls using some fieldbus, you should be actually posting details about the controller. KRC2 is old and has limited resources. newer KRC2ed05 have more powerful PC with more memory, and use newer software including DeviceNet drivers.

    then there is the AC power. you can get 120VAC only from NA controllers because they have transformer. but the 120VAC secondary is only good for up to 4.5A. really it is meant for light load such as cabinet lighting, user receptacle etc.

    750-504 has transistor outputs. it is operating at 24VDC. to work with 120VAC you need to add relays or use different module.

    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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