How do I electrically disconnect my Z axis limit switches


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Thread: How do I electrically disconnect my Z axis limit switches

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    Default How do I electrically disconnect my Z axis limit switches

    Some help would be much appreciated. I need to replace my limit switch wiring with screen cable due to random estops caused by EMI interference from my high speed spindle which uses a dedicated VFD. For the life of me I cannot find how to gain access to the electrical terminals on the TZ7311 limit switches?

    How do I electrically disconnect my Z axis limit switches-tz7311-jpg

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    Default Re: How do I electrically disconnect my Z axis limit switches

    I expect the black terminal cover is just clipped onto the switch
    there is not enough detail in your photo to see if any clips are visible

    as an example , this from RS Components
    ZC-Q2255 | IP67 Snap Action Limit Switch, Plunger,, NO/NC, 250V | Omron

    see page 9
    How do I electrically disconnect my Z axis limit switches-0900766b803561b9-pdf


    John



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    Default Re: How do I electrically disconnect my Z axis limit switches

    The black terminal will pop off with the use of a small regular screw driver. Once removed you will find three screws. Com, NO, NC. In most cases the COM and NC are the contacts used. You will probably need more than just shielded cable to fix your issue. Check all the grounding and depending on the controller you are using moving the limit circuit to a 24V logic circuit would probably fix your issue. Really this just means you would run 24V through all of the limit switches to a 24V relay. The contact of the relay will then tie to the breakout board you are using. The relay would be activated when all is correct, so you would use COM and NC to go to the breakout board to generate the LIMIT error.

    Russ



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by john-100 View Post
    I expect the black terminal cover is just clipped onto the switch
    there is not enough detail in your photo to see if any clips are visible

    as an example , this from RS Components
    ZC-Q2255 | IP67 Snap Action Limit Switch, Plunger,, NO/NC, 250V | Omron
    John
    Bingo. I guess I'm getting to cautious in my old age, although the clip-on was not so obvious as in your example.

    Thanks John.

    Phil



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by CNCMAN172 View Post
    The black terminal will pop off with the use of a small regular screw driver. Once removed you will find three screws. Com, NO, NC. In most cases the COM and NC are the contacts used. You will probably need more than just shielded cable to fix your issue. Check all the grounding and depending on the controller you are using moving the limit circuit to a 24V logic circuit would probably fix your issue. Really this just means you would run 24V through all of the limit switches to a 24V relay. The contact of the relay will then tie to the breakout board you are using. The relay would be activated when all is correct, so you would use COM and NC to go to the breakout board to generate the LIMIT error.

    Russ
    Thanks for the input Russ, it is very much appreciated. I've already earthed every which way. I realise that upping the voltage will greatly improve the situation. However as shielding is a relatively easy option and I already have some suitable cable I will probably try that first. I've already managed to reduce the number of trips from 1 a minute to 1 in about 30 minutes. Is there anyway to determine which axis is the culprit?

    I see that the Tormach installation manual for their high speed spindle doesn't even address EMI, am I missing something?

    Phil



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Philbur,
    You can look for errors on the MACH3/4 screen but usually EMI errors happen so fast the CNC software does not even see it happen. Many times it just loses control and suddenly you can't get the CNC software to respond at all. Shielded is a good step but I will be really surprised if that alone will fix your issue.

    Good Luck
    Russ



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by CNCMAN172 View Post
    Philbur,
    You can look for errors on the MACH3/4 screen but usually EMI errors happen so fast the CNC software does not even see it happen. Many times it just loses control and suddenly you can't get the CNC software to respond at all. Shielded is a good step but I will be really surprised if that alone will fix your issue.

    Good Luck
    Russ
    OK thanks for that. I'll start to look at what I need to do to up the voltage. there's not a great deal of room in the cabinet to add a relay and probably a transformer. MACH3 doesn't hang when the estop is tripped, in fact if I reset and then click run it continues as if nothing has happened, which surprised me.



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Philbur,
    Which controller are you using? Is it a USB type controller or Ethernet? If this is a USB interface to the PC another thing you can add to help with EMI is a USB isolator.

    Russ



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by CNCMAN172 View Post
    Philbur,
    Which controller are you using? Is it a USB type controller or Ethernet? If this is a USB interface to the PC another thing you can add to help with EMI is a USB isolator.

    Russ
    The interface between PC and machine is via a parallel printer cable.

    Phil



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by philbur View Post
    Some help would be much appreciated. I need to replace my limit switch wiring with screen cable due to random estops caused by EMI interference from my high speed spindle which uses a dedicated VFD. For the life of me I cannot find how to gain access to the electrical terminals on the TZ7311 limit switches?

    How do I electrically disconnect my Z axis limit switches-tz7311-jpg
    If you've identified the VFD / High speed spindle to be the cause I'd start looking there to reduce the noise rather than on the switches. You say you're using a dedicated VFD? Not the Tormach system?
    Step


    Sent from my iPhone using Tapatalk



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Quote Originally Posted by TurboStep View Post
    If you've identified the VFD / High speed spindle to be the cause I'd start looking there to reduce the noise rather than on the switches. You say you're using a dedicated VFD? Not the Tormach system?
    Step

    Sent from my iPhone using Tapatalk
    Thanks for the input Step. From what I have managed to find on the internet the general consensus is that it is necessary to tackle the problem on all fronts. I think I have already done all I can with the spindle and dedicated VFD (not the Tormach VFD). Low voltage and lack of screening on the limit switch circuit seems to be a common denominator with most commentators, hence my current focus.

    Phil



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    Default Re: How do I electrically disconnect my Z axis limit switches

    Philbur,

    You can isolate the limit switch inputs to the breakout board using opto isolators or relays. Here is a diagram so you can understand. This will stop the ESTOP issue you are seeing. If you are using the LIMITS as HOME sensors as well you will need one per AXIS.

    How do I electrically disconnect my Z axis limit switches-24v-logic-jpg

    Russ



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How do I electrically disconnect my Z axis limit switches
How do I electrically disconnect my Z axis limit switches