Setting up some I/O on a KRC2 ed. 2005

  • Hi folks, first post here...

    I have bought a KUKA KR6-ARC with a KRC2-Ed. 2005 controller as part of a personnal creative workshop.
    My background of 3D modeler helps me with the programming of the robot since I use 3D models (Rhino) and visual programming (Grasshopper + KUKA|PRC).…p5aMvduRwy0u7lozdAryhVDkk
    But on the electronics side, I am a complete idiot.

    Now I would like to hook-up a Powermax Plasma cutter, but I need to set up I/O ports to control the start and stop of the torch and recieve the info that the kinematic can start (when arc is established).
    I have found lots of info on this Forum already, and I know that I need to find a devicenet cable (the one usualy labeled X801) that I can plug on the Combicon port of my MFC card.
    Then I need a Beckhoff Devicenet coupler + Input terminal + Output terminal, but I can't seem to figure out which models I should order.

    A friend of mine who owns a KRC4 gave me some references which I purchased, just to find out that they use the Ethercat protocol which is not compatible with KRC2 (or so I think).
    As a side note, I have A Beckhoff EK1100 + EL 4104 (4 chanel analog output) + EL 3064 (4 chanel analog intput) for sale right now for this reason...

    Also, the KUKA Devicenet manual mentions a "Multi-power tap" to feed 24V to the Devicenet modules, but I can't seem to find it in my bay ; where is it supposed to be located, or if I don't have it, where should I get these 24 V from ?

    Cheers, and thanks in advance.

  • Interesting.... that 'X' card looks like fiber-optic Interbus. The 'Y' card I'm not sure about, but it could be electrical Interbus. Not that that helps you, unfortunately.

    Anyway, the DeviceNet bus does *not* get its power from the card in the KRC. DeviceNet bus power needs to be provided separately -- there are power supplies you can buy that provide the requisite high-quality 24VDC. You can steal the bus power from the robot's spare internal 27VDC contacts, but that can be a bit unreliable, so the best resort is to purchase a qualified DeviceNet power supply.
    Then, technically, output power is supposed to have a separate power supply, which can be of a different voltage and lower quality. A lot of people cheat here and just cross-wire the bus power into the output power, which generally works if your outputs are 24VDC. But if your outputs need to run a different voltage, or pose a risk of shorts, spikes, etc, you really want to isolate that power from the bus power -- otherwise, you risk a voltage event not just frying your output card, but possibly making it all the way back to your (much more expensive) MFC card in the KRC. Less catastrophically, you could still be risking voltage events (and a plasma cutter generates a lot of electrical noise) causing your bus to become unreliable.

  • Hi Mister Leg, KonstantinosP,

    and thanks for your help !

    I attached the crude schematics of the setup for I-O between the plasma and the Robot.
    As you can see, I'm a complete newb.

    First, ("A" and "B" question marks) : I can see the input and output terminals, but where should I plug the second wire ?
    I'm also confused by the +24V power contacts on Digital modules, specially on the input since it is suppose to recieve voltage, not generate it...
    Should I have a dedicated 24 VDC supply for these modules ?

    Second, ("C" question mark) : where should I plug the ground coming from my plasma ?

    Finaly, ("D" question mark) I have an analog signal from my plasma which is the arc voltage of the plasma divided by some value.
    This allows to know if the torch height should be adjusted.
    But with a "single ended" Analog input module, I don't know where to plug the second wire. Should I use a "Differential" version instead ?

    Yeah, I know, I'm really at the bottom of the learning curve... I'm happy I found this Forum.


  • > I'm also confused by the +24V power contacts on Digital modules, specially on the input since it is suppose to recieve voltage, not generate it...

    The +24V pins are connected to the Beckhoff's bus voltage, so there's always 24V present in those pins.

  • get someone knowledgeable to help you with this (someone who can read datasheets).

    on most modules top and bottom rows of terminals are I/Os and middle two rows are power (top middle is 24VDC, bottom middle is 0VDC).

    when using output module to power load (such as relay coil in your case), use output terminal (as you have) to connect one side of relay coil. the other side of relay coil goes to 0VDC (usual, PNP output) or 24VDC (mainly in Japan, NPN output).

    when using input module to receive signal from a device (such as relay contact from Plasma unit), use input terminal (as you have) to connect one side of relay contact. the other side of relay contact goes to 24VDC (usual, PNP input) or 0VDC (mainly in Japan, NPN input).

    wiring of analog I/O follows PNP logic (just have range of values). beware that analog output from Plasma is not standard output. most analog inputs are 0-10V, -10..+10V or less. This analog signal is up to 18V so you need extended range analog input card or voltage divider.

    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

  • Hi,

    I am not experienced with PLASMA but the topics calls me to write something helpful in terms of electrical circuitry.

    @Wall_E, the basics of control voltage electrical is that you have to have a common ground/neutral/-ve voltage in order to recognize the +ve potential by all the devices in circuit. So, the answer to your question about digital inputs (why they have +24VDC) is that some of the IO cards works on reference voltage functionality which works on comparison between the +24VDC supply and the voltage at IO inputs and therefore, they need a common ground to perform this evaluation. If the difference would be higher then the IO will not be recognized.

    Thus, the wire "A" should be connected to the same 0 VDC where your IO cards' 0 VDC is connected. All the negative voltage should be the same if you want your circuit to work without any problem.

    You have to explain more about Transfer (start machine motion) to get the answer about wire "B" as I already mentioned that I am not experienced with PLASMA. I may or may not be helpful in this case.

    Wire "C" is Ground which means you have to connect this to PE terminals. You should be connecting electronic ground to your controller which means having an electronic ground earth pit and connecting cables wherever needed. Well, I must admit it is the most neglected aspect of electrical/electronics but it is the most significant part of any circuit.

    For wire "D", first you have to ensure the mode of operation in which you get the desired voltage readable by your Beckoff Analog Input card. Mostly, it is 0 to 10 VDC (please go through Beckoff manual for it). You also have to read about PLASMA voltage divider and choose from the ratios (20:1, 21.1:1, 30:1, 40:1, 50:1) and see which one is optimum in your application. Now, about the connection wire 6 (+ve) should go to the positive terminal of the input port of Beckoff Analog card and wire 5 (-ve) should go to the negative terminal of the input port of Beckoff Analog Card.


  • Hi Panic, RS,

    Thank you so much. I'm starting to get a feel for this wiring business.
    I attached a schematics of my setup based on what I understood.

    There's also an explanation about the "Transfer" thing.
    Regarding the voltage divider, if I choose the 1:40 ratio, the tension from the plasma should always be below 9V.
    I supposed that I needed a "Differential" analog input instead of a "Single ended" to read the "divided arc signal".

    Finally, I hooked the "Ground" of my plasma to one of the "0V" power contacts ; since they are all on the same line, I suppose I could plug this in any of the I-O modules.

    Thanks to you guys, I've moved one step closer to being "someone who can read data sheets" :icon_wink:


  • Ok, there is another thing which I noticed in old and new picture. There can be another valid use of +24 VDC circuit on the input IO card in Beckoff. You can connect a relay in the circuit in order to protect both the components (PLASMA and Beckoff Input card). I made the changes in the picture for you and you can understand it better what I mean to say. I think this would be the best way to make your electrical circuit.

    For analog channel, you have to be sure that the ratio is applicable. If not then you have to follow Panic's suggestion or to do some adjustments in robot program.


  • Hi RS,

    I don't think that this will work because on the Plasma side, there is never any tension between 12 and 14 : it is just a dry contact closure.
    But what might be wrong with my wiring is that, when the plasma closes the circuit, I will have a 24 V input in a module which accepts 0-10V.

    So I drew a new schematic (V3 !) with a tension divider circuit.

    Does this make sense ?


  • no no nooo...

    i did mention you need someone who can interpret datasheet... (such as
    there is no voltage divider needed for KL1104, this is a 24V input module...

    of course same applies to any of connections - it is your job to ensure that interfaces are compatible.

    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

  • Hi folks,

    I ordered a fancy 24VDC power supply.
    It says "Devicenet" on the side...sounds promissing.
    It even has two outputs, so I can supply the coupler and the modules separately, as suggested.

    Now...errr.. where do I get the 220V from ?
    Is it preferable to get the juice from outside the cabinet, or is there a power supply in the KRC2 for this purpose ?


  • I guess you have to arrange from outside of KRC2 cabinet. A dedicated 220 V supply to power up this power supply. I would recommend you to go with a UPS 220 V supply.

    BTW, is the input of this power supply is in the range of 100 to 220 V? If yes, then you can also go with 100 VAC.


  • Going by the photo, this power supply can accept anything from 100-240VAC. Rather like most modern laptop power supplies. So just running it from normal mains should be fine. There aren't any circuits inside the KRC that run less than 280VAC, IIRC, so an external power supply will be necessary.

    The good news is, DeviceNet power can be sourced from anywhere along the bus. So you don't have to have this brick inside the KRC -- it can be connected at any convenient location along the DeviceNet cable.

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