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  1. #1

    Join Date
    Apr 2020

    Mk3/4 Wiring problem

    Hi, I am new to this forum and a new customer of PlanetCNC. I am rebuilding a lathe with a MK3/4 board, PlanetCNC output board, new stepper drivers, stepper motors and a VFD and am part way through wiring the control cabinet. I am having an issue with the controller board losing connection with the PC when I run the VFD and start the spindle motor. By a process of elimination I have narrowed this down, when the controller is powered by the external 12V power supply the problem happens but when the controller is just powered by USB it doesn't. It is obviously some sort of interference or grounding issue but I can't work out what.

    I am using a quality, short, double shielded USB cable. The cable to the spindle motor from the VFD is shielded. Other wires are not shielded. I have disconnected all outputs and inputs from the controller to diagnose the issue. I am running the VFD directly (not through the software). The VFD is not connected to the output board yet. The 12V power supply is powering both the controller and output board - is that an issue or do I need separate power supplies? All components are attached to the metal cabinet and this is earthed. The power supplies are connected to earth. The controller board and output board are mounted on steel standoffs with paper washers. Power for the power supplies and VFD comes from a single mains socket.

    I would really appreciate any ideas on what is wrong. Would it help to use shielded cable from the power supply to the controller and output boards?


  2. #2
    Join Date
    Jun 2017

    Re: Mk3/4 Wiring problem

    You didn't mention if you had an EMI filter on the input power the the VFD. One of those is crucial to stop the noise from the VFD getting back into other components. Also even though you have a short shielded USB cable make sure it is routed away from the VFD cable and definitely not running paralell.

  3. #3

    Join Date
    Apr 2020

    Re: Mk3/4 Wiring problem

    Thanks - I dont have an EMI filter for the VFD

  4. #4
    Join Date
    Mar 2017

    Re: Mk3/4 Wiring problem

    I use "Schaffner AX-FIM1024-SE-LL" filter for VFDs in most of my projects.

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