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Thread: Strange issue with Z Zero touch plates.

  1. #41
    Member mactec54's Avatar
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    Default Re: Strange issue with Z Zero touch plates.

    Quote Originally Posted by jimskeet View Post
    Ok I got a new adapter today. The previous adapter was glued on the control box so I decided to test the new adapter before removing the old one just to be sure... I connected the new adapter and again the proximity switches were not working. Their leds didn't light up and it was like they didn't get any power. I connected the old one again and after moving pushing the cable connection back and forth I could find spots that it was working and spots that it didn't.
    So then it struck me that maybe there is not an issue with the adapter and had something to do with where the adapter was touching. The next test proved me right.
    When I touched the metal surrounding of the adapter on the sheet metal that the connectors are held the switches get powered on and work. When the adaptor is not touching the sheet metal the switches get powered down...

    So something is weird with the connections.

    I also tested this. I touched a cable on the metal case of the adaptor and the -12v supply and again the switches powered on. So for today I connected a cable on the small bolt that the parallel cable screws on to and connected the other end on the -12v so the machine worked the whole day fine.
    It seems that they have wired the power supplies Negative to Ground, this is not unusual, but can cause lots of problems, like you are seeing now, and may be where the other problems came from as well, it also means the low voltage is shearing the same Ground as the high voltage, if something goes wrong on the high voltage side, it will fry everything on the low voltage side

    Mactec54


  2. #42
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    Default Re: Strange issue with Z Zero touch plates.

    Hmm at which point do you think the wiring is wrong? At the main supply 230v connections?

    Last edited by jimskeet; 02-04-2018 at 02:56 AM.


  3. #43
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    Default Re: Strange issue with Z Zero touch plates.

    Just to make it clear. Only the proximity switches do not work when the metal case of the adaptor is not touching the metal case of the control box. The rest of the machine works fine. Spindle works, axis motion is normal and the other inputs too.

    Maybe the input connections of the 12v supply are not connected right?
    I mean the neutral is connected to the ground input and the ground input to the neutral?

    Because since the bob and machine works fine without the adaptor touching the ground that means that the 5v supply is fine? And something is happening only on the 12v supply? Do I miss something?

    Last edited by jimskeet; 02-04-2018 at 05:04 AM.


  4. #44
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    Default Re: Strange issue with Z Zero touch plates.

    After some research today I found this thread.
    https://www.machsupport.com/forum/in...c,9587.30.html
    I read in this that the all the common connections of the DC power supplies should be connected together to a single point. And that many power supplies have the common pulled to the ground to avoid some noise issues and that you should not connect other common connections to ground.

    So, on my control box the -12v and -5v are not connected together. From what I understand from the thread I linked they should be connected together? This is the reason that the switches do net get power when the adaptor is not touching the ground since there is no return path to -12v?
    Also when the metal of the adaptor touches the metal of the box which is grounded, it leads to the commons being again connected to ground, the proximity switches now have a return path to the power supply and power on but since they use the ground maybe this is creating the noise issues with the touch plates? Do I think this right? Also could this create the Overcurrent faults I get on my VFD some times?

    Should I isolate the parallel adaptor from the metal frame so it is not in contact with ground and connect the -12v and -5v together with a cable?



  5. #45
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    Default Re: Strange issue with Z Zero touch plates.

    Quote Originally Posted by jimskeet View Post
    After some research today I found this thread.
    https://www.machsupport.com/forum/in...c,9587.30.html
    I read in this that the all the common connections of the DC power supplies should be connected together to a single point. And that many power supplies have the common pulled to the ground to avoid some noise issues and that you should not connect other common connections to ground.

    So, on my control box the -12v and -5v are not connected together. From what I understand from the thread I linked they should be connected together? This is the reason that the switches do net get power when the adaptor is not touching the ground since there is no return path to -12v?
    Also when the metal of the adaptor touches the metal of the box which is grounded, it leads to the commons being again connected to ground, the proximity switches now have a return path to the power supply and power on but since they use the ground maybe this is creating the noise issues with the touch plates? Do I think this right? Also could this create the Overcurrent faults I get on my VFD some times?

    Should I isolate the parallel adaptor from the metal frame so it is not in contact with ground and connect the -12v and -5v together with a cable?
    I would not go to much by what you read, no the 5v and the 12v should not have the commons connected at the same point, this is only done in an extreme case, when it has been determined that they are the source of the problem, the common is the return path for each of the power supplies, and should in your case remain like that, it seems though that your 12v common has been connected to the High voltage Ground, or to the metal cabinet, as I said in the last post, this can cause the problems you are having

    Mactec54


  6. #46
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    Default Re: Strange issue with Z Zero touch plates.

    Thanks for the answer. I measured 0 resistance between the -12v connection and the metal frame inside the box. So the -12v is connected with ground as you say. But is this happening internally in the power supply? Also if I isolate the adaptor from the frame, how should the proximity sensors close the circuit with the -12v because from what I understand, now they close the circuit via the ground and when I isolate the adaptor from the metal case they power down.
    Here is a more detailed drawing of how the connections are done at the moment.



    As you see if not via the ground there is no return path from the switch to -12v.

    Attached Thumbnails Attached Thumbnails Strange issue with Z Zero touch plates.-control-box-jpg  


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Strange issue with Z Zero touch plates.

Strange issue with Z Zero touch plates.