Thread: Usbcnc

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  1. #1
    Hi all,
    I was wondering if anyone has any experience on USBCNC and the CPU4 controller pcb?
    I will be using this kit for my machine build and was looking for some tips.



  2. Hi Ian, USBCNC is fantastic. i have been using it for about 6 months now and not a single problem with it, its super stable over ethernet thats what i would recommend doing if you have the CPU4 with ethernet! also if you have any problems or questions just e-mail bert who designed, built and wrote the software.

    Also the software is just as easy to customise as Mach 3 in my opinion its a lot better then mach!

    Thats my 2p worth


  3. #3
    I am going to be using the CPU4 card with USB connection. If you are using the CPU4 card how did you wire your limit switches?


  4. Hi Ian, Im using a CPU5A4E card but the CPU4 will be much the same when it comes to wiring up the switches.

    If you have looked at the CPU4 diagram you will see the home connector, this it easy to wire up. looking at the pin out table in the link you will see pin 1 = X home 2 = A home 3 = Y home 4 = B home 5 = Z home 6 = GND Pin 7 is if you have supplied an external 5v supply to the card (ignore of you have not) 8 = GND 9 = 5v USB (if you are powering the card from the USB port.

    So if you were wiring the card up in a normal case suituation then you would ideally be using a NC switch, you would run a wire from pin 1 ( x home) to your switch, from the switch back to ither pin 6 or pin 8 (GND) the same goes for the other axis.

    Thats about it matey ;)


  5. #5
    I take it that the home switches also act as limit switches for each axis? Did you use seperate switches for your e stop or use the home switch as well? I was going to add an e stop switch at the end of each axis. The only problem I will have is that my proximity switches need between 10 to 30v to work correctly so I will need to connect them to a relay and get the relay to switch the CPU4 signal, not a big problem but it needs to work correctly.


  6. Yes mate, the switches act like limits and e-stops, there are setting in the software to tell usbcnc how you want it to use the switches.

    I also have proximity switches, these run off 12v, it is pretty easy to wire up. once you have it all ready for wiring then give me a shout and ill try and help you if you get stuck.

  7. #7
    Did you fit a limit switch to each end of your axis? Ie one limit at the end of + x axis and another at the end of - x axis and the same for the Y and C axes and also an e stop switch at the end of each axis? I am trying to get the idea of how the switching is designed to work. I am used to seeing an end limit switch and an e stop switch at the end of travel for each axis. Obviously the CPU4 card does not have the connections for this type of wiring so is the best idea to fit a home limit at say the + end of travel for each axis and connect them all up to the home connector, then I was thinking about fitting an e stop switch at both ends of travel for each axis and dasiy chain them to the e stop connector seeing as the card does not have seperate inputs for each axis for an e stop signal.



  8. Ian, USBCNC is configured much simpler than this, all that is needed to be done is place a limit switch at the Home of each axis. then in the software you tel it how much travel each axis has (effective table size) once this is done each time you Launce the software it will ask you to reference the machine, depending on what order you configure each axis, it will slowly move the axis up to the switch and then back off until it see continuity of that switch again. mine is set to reference Z then Y then X. once this is done the switches then act like e-stops, so (if) soon as the axis is triggered the software will stop and disable the Stepper/Servo Drives and any other things like coolant pumps you may have setup.

    Also unlike mach3 the switched have there own input so the software knows what switch has been activated.

    Hope that helps


  9. #9
    Thanks for the info. I think I have it now. It just seemed to be too simple to be like that.
    I can get it done with three limit switches now instead of six that I had planned for. Although I might add an extra switch at the opposite end of each axis travel for some extra safety and connect it to the e stop.


  10. I suppose adding 3 more would not hurt anything but tbh i really dont see the need, have a look at the manual on the USBCNC site it tells you how best to set the switches up.


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