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Limit switch consensus.

Discussion in 'CNC Mills/Routers' started by ca. 280, Nov 5, 2020.

  1. ca. 280

    ca. 280 New
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    The Net's glory is also it's curse, there are so many conflicting wiring diagrams, some old some new. Is there a 2020 consensus on the best way to install limit switches? i.e. normally open, normally closed, installing capacitors for buffers, looping positive, looping negative and on and on. System is Arduino UNO, grbl 1.1h, Candle 1.1.7.
    Any comments appreciated.
    A wiring diagram would be very helpful.
     
  2. Giarc

    Giarc OpenBuilds Team
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    The best information is in the limit switch part of the wiki. gnea/grbl The easiest thing for filtering are the Xtension Limit Switch Kit with built in filtering. I bought some for my new lathe and love them. So easy to set up. For my first CNC, I bought all the individual components (capacitors etc) an made my own.
     
    sharmstr likes this.
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Xtension Limit Switch Kit on a BlackBox, both of which is loaded with signal filtering circuitry, still normally open for easier config and wiring, while all the filters remove the EMI that otherwise makes people dislike Normally Open
     
    #3 Peter Van Der Walt, Nov 5, 2020
    Last edited: Nov 5, 2020
  4. ca. 280

    ca. 280 New
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    Thanks for responding.
    This is kind of my point. That site shows the limit switches on UNO pins 9,10 and 12 which I am told (see my post under "pin conflict") changed years ago
    and now use pins 9,10 and 11. I also found a post saying all that was required for suppression was a 47uF capacitor across each pin to ground. But that was for V.08 not 1.1, still valid?? Have also found diagrams that loop 5v thru the switch to the UNO and others that loop ground. Very confusing!! Was hoping to find something
    up to date and in agreement.
     
  5. ca. 280

    ca. 280 New
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    Thanks again Peter,
    What's your take on the capacitor theory as above??
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Refer the Docs: gnea/grbl
    Read the WHOLE grbl-Wiki :) - knowledge is power

    47uf is crazy. More like 0.1uF
     
  7. Giarc

    Giarc OpenBuilds Team
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    No. 9,10, and 12 are current in GRBL 1.1 gnea/grbl

    I just use capacitors to ground and I use GRBL 1.1. However, I milled out a pcb and bought all the components a couple years ago to make the GRBL filtering board shown on the wiki. I plan to finish it since my CNC router uses a 36v power supply. Otherwise I would have just bought the Openbuilds extension switches.

    ** Edit. I guess Peter posted while I was typing
     
  8. ca. 280

    ca. 280 New
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    These are the images I have of limit switch pin assignment. limit switch to arduino.jpg UNO pin layout.jpg
    Was told, by Peter, that the old pin assignment applied to V0.8??
    Still not sure if the UNO is looking for a closure to ground or 5v.
    Sorry about the typing error, should be .47uF
     
    #8 ca. 280, Nov 5, 2020
    Last edited: Nov 5, 2020
  9. ca. 280

    ca. 280 New
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    This was the poster on my EE sites logic. Again refers to 9, 10 and11. Were just trying to get this right not cause conflicts. ROUTER BASE 200024.jpg
     
  10. ca. 280

    ca. 280 New
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    So I finally found the grbl/wiki for 1.1 that everyone was referring to and had my questions answered.
    Many thanks for your patience. Any thoughts on my last post about the capacitor logic?? ignoring
    the wrong pin locations??
     
  11. SeanD

    SeanD Well-Known
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    Here is my input on normally opened vs normally closed. If you have physical access to all areas of your machine and enough cable to reach all of your limit switches from your control box then make them normally open and wire the limit switches individually.

    If however you want to limit the cabling or have limited physical access, wire the limit switches in series and set them to normally closed. This will allow the limit switches still to trigger whilst homing but you lose the diagnostics part when working out which limit switch is being triggered. When one is triggered they all are.

    Have previously had both series and individually wired working just fine with the OpenBuilds Blackbox.
     
  12. phil from seattle

    phil from seattle Journeyman
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    On the capacitors, the poster who recommended that didn't understand why you use them.

    They form part of a Low Pass Filter is causes higher frequency signals to be attenuated (reduced) but low frequency signals (like switch closure) pass just fine. It also needs a resistor to be effective. Look here for an explanation with a diagram. With a resistor of 1K Ohms and a capacitor of 100n (0.1 uF), you will lose most of the noise coming in. A lot of breakout boards have these built in and they really do work.
     
  13. Giarc

    Giarc OpenBuilds Team
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    Where did you find those pictures? Definitely not at the official GRBL Wiki. That pin assignment is from GRBL 0.8 if I recall correctly. This is from the link above I mentioned. You can see the correct pin out. [​IMG]
     
  14. Christian James

    Christian James Journeyman
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    limit switches.jpg Here's a drawing I did a couple of years ago - worked fine although I don't bother with limit switches these days.
     
    #14 Christian James, Nov 6, 2020
    Last edited: Nov 6, 2020
  15. ca. 280

    ca. 280 New
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    Thanks everyone for the comments and assistance, much appreciated.
     

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