How do I electrically disconnect my Z axis limit switches


Page 1 of 3 123 LastLast
Results 1 to 20 of 42

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

  1. #1
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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

    Similar Threads:


  2. #2
    Member john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    2083
    Downloads
    0
    Uploads
    0

    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



  3. #3
    Member
    Join Date
    Jun 2005
    Location
    USA
    Posts
    1723
    Downloads
    0
    Uploads
    0

    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



  4. #4
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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



  5. #5
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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



  6. #6
    Member
    Join Date
    Jun 2005
    Location
    USA
    Posts
    1723
    Downloads
    0
    Uploads
    0

    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



  7. #7
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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.



  8. #8
    Member
    Join Date
    Jun 2005
    Location
    USA
    Posts
    1723
    Downloads
    0
    Uploads
    0

    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



  9. #9
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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



  10. #10
    Member
    Join Date
    Dec 2008
    Location
    Switzerland
    Posts
    740
    Downloads
    0
    Uploads
    0

    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



  11. #11
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

    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



  12. #12
    Member
    Join Date
    Jun 2005
    Location
    USA
    Posts
    1723
    Downloads
    0
    Uploads
    0

    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



  13. #13
    Member
    Join Date
    Jan 2007
    Location
    USA
    Posts
    94
    Downloads
    0
    Uploads
    0

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

    A better approach would be to suppress the EMI at the source. I would first try a shielded power cable from the VFD to the motor.


    Sent from my iPhone using Tapatalk



  14. #14
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

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

    Quote Originally Posted by lens42 View Post
    A better approach would be to suppress the EMI at the source. I would first try a shielded power cable from the VFD to the motor.


    Sent from my iPhone using Tapatalk
    Thanks for the input Lens42, but as I said I think I have already done all I can with the spindle and dedicated VFD. This includes a shielded cable from the VFD to the motor, as short as possible and grounded at both ends.

    Phil



  15. #15
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

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

    Quote Originally Posted by CNCMAN172 View Post
    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.

    Russ
    Thanks for the diagram, I'm not sure I understand VCC or the second 2 in 2K2.

    Phil



  16. #16
    Member john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    2083
    Downloads
    0
    Uploads
    0

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

    Hi Phil
    VCC is the positive supply to the switch
    the resistor is 2200 ohms = 2.2K = 2K2
    ( the K is very often put in place of the decimal point so its not lost in poor copies of the diagram or stray spots taken as decimal points )

    I would re-arrange the circuit to put the limit switch in the ground connection to the opto-isolator
    so you can't short circuit the + 12V or 24V supply

    How do I electrically disconnect my Z axis limit switches-12v-24v-logic-jpg

    John



  17. #17
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

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

    My limit switches are currently wired as normally closed, can I stick with this or do I need to wire them normally open, or something else.

    Phil



  18. #18
    Gold Member MichaelHenry's Avatar
    Join Date
    Jun 2006
    Location
    Chicago suburbs
    Posts
    3063
    Downloads
    0
    Uploads
    0

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

    Phil - is this problem on your original PCNC 1100? My S/N 119 1100 was giving me intermittent limit switch E-stops which went away when Tormach sent me a ferrite that looks something like this one to install on the parallel port cable.

    Laird Technologies - HFA150068-0A2 - High Freq 275 Ohms @300MHz 0.266In Max I.D. EMI Ferrite Split Snap-On Core - Allied Electronics

    Tormach sells one here:

    https://www.tormach.com/store/index....show&ref=30749



  19. #19
    Gold Member
    Join Date
    Jun 2006
    Location
    Suffolk, UK
    Posts
    2512
    Downloads
    0
    Uploads
    0

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

    Quote Originally Posted by MichaelHenry View Post
    Phil - is this problem on your original PCNC 1100? My S/N 119 1100 was giving me intermittent limit switch E-stops which went away when Tormach sent me a ferrite that looks something like this one to install on the parallel port cable.

    Laird Technologies - HFA150068-0A2 - High Freq 275 Ohms @300MHz 0.266In Max I.D. EMI Ferrite Split Snap-On Core - Allied Electronics

    Tormach sells one here:

    https://www.tormach.com/store/index....show&ref=30749
    Hi Michael thanks for the info it is much appreciated. I was starting to wonder about the printer cable. There seems to be a wide range of impedance and frequencies for ferrite cores. Is the Laird one you list the same spec as the one supplied by Tormach.

    Phil

    PS: yes it is on my original PCNC1100 serial number #037. which end of the cable did you install it?



  20. #20
    Registered
    Join Date
    Aug 2016
    Posts
    7
    Downloads
    0
    Uploads
    0

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

    Quote Originally Posted by philbur View Post
    Is there anyway to determine which axis is the culprit?
    I just went through this same VFD noise problem. To isolate which limit switch that was falesly tripping, I moved all 3 axis well away from the limit switches. Then I went into the Mach3 Config screen and disabled the limit switches one at a time until the problem went away. On my setup, the noise was coming from the Z-axis limit switches. I guess it's expected as they sit close to the spindle. I'm running with an ethernet Smootstepper and to fix the issue, I added some noise filtering to the limits on the ethernet Smoothstepper config screen.

    One other thing I noticed that helped with the noise is adjusting the carrier frequency on the VFD. There seemed to be sweet spots wrt minimizing the noise. I checked it with an oscilloscope and for me, 9KHz was the best.



Page 1 of 3 123 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

How do I electrically disconnect my Z axis limit switches

How do I electrically disconnect my Z axis limit switches