Welcome to Our Community

Some features disabled for guests. Register Today.

Sign Up

Limit switches - Normally Open Vs. Normally Closed

Discussion in 'Controller Boards' started by doug@towerleather, Oct 24, 2019.

Tags:
  1. doug@towerleather

    doug@towerleather New
    Builder

    Joined:
    Apr 13, 2016
    Messages:
    3
    Likes Received:
    0
    Hi folks,

    I just picked up several Xtension limit switches to replace some damaged micro switches. I originally had my switches Normally Closed. That way if the wire was damaged the machine would stop. My understanding was this is safer than Normally Open where a wire failure would not be caught. Am I missing something? Is there an advantage to using Normally Opened that I am not aware of?

    Also, is there a schematic for Xtension limit switches somewhere?

    Doug
     
    #1 doug@towerleather, Oct 24, 2019
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,003
    Likes Received:
    4,114
    Xtension Switches have onboard RC noise filtering, so no real need for normally closed.
    The main advantage is the default Grbl config is for NO switches, you need to first change $5-setting for NC switches.
    NO also allows easier wiring of the min/max switches as you can just parallel them - no need for complicated series wiring schemes
     
    #2 Peter Van Der Walt, Oct 24, 2019
    MaryD likes this.
  3. Ferreri

    Ferreri New
    Builder

    Joined:
    Feb 1, 2017
    Messages:
    22
    Likes Received:
    5

    So, IS there a schematic available for these switches?
     
    #3 Ferreri, Jan 1, 2020
  4. brrian

    brrian Well-Known
    Builder

    Joined:
    Dec 6, 2019
    Messages:
    118
    Likes Received:
    51
    I think I'm going to run Xtension limit switches all the way around my machine. I also wondered if there's a wiring diagram, didn't find one, so made my own. See attached. I think it's this simple... hopefully somebody will confirm?
     

    Attached Files:

    #4 brrian, Jan 1, 2020
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,003
    Likes Received:
    4,114
    Plan looks good! Should work just fine
     
    #5 Peter Van Der Walt, Jan 1, 2020
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,003
    Likes Received:
    4,114
    Not at this time, very simple though, switch wired NO with a 10k pullup , RC filter on SIGNAL line, and an Indicator LED :)
     
    #6 Peter Van Der Walt, Jan 1, 2020
    Ferreri likes this.
  7. Ferreri

    Ferreri New
    Builder

    Joined:
    Feb 1, 2017
    Messages:
    22
    Likes Received:
    5
    Thanks guys, I was mostly curious about the component values for the noise filtering.
     
    #7 Ferreri, Jan 2, 2020
  8. RyanH

    RyanH New
    Builder

    Joined:
    Sep 20, 2020
    Messages:
    1
    Likes Received:
    0
    I am setting my machine up to use the dual axis homing feature in GRBL, which requires the switches to be wired in a NC configuration rather than NO, and using NO is not an option for me. Is there any way to wire these switches in the NC without having to solder the wires directly to the switch itself? I validated the switch itself could be used as NC... but unless there is solder jumper or something, it looks like the only option I have is to solder the wires directly to the switches to make it work. If there is not, it will be extremely disappointing as the more generic switches which were sold by openbuilds and no longer available didn't have this limitation, and the OpenBuilds Store makes no mention anywhere that these switches can only be used in a NO configuration.
     
    #8 RyanH, Sep 20, 2020
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Mar 1, 2017
    Messages:
    14,003
    Likes Received:
    4,114
    That is not true. You can wire the Y2 switch in parallel to Z as normally open. Grbl relies on the homing order (z first, then XY to differentiate)
    Read the relevant sections of config.h

    Also, dual homing sounds good but its much easier to build the machine square from the beginning (we played with it a lot, in practice its harder to setup those to switches to be square
     
    #9 Peter Van Der Walt, Sep 21, 2020
    Last edited: Sep 21, 2020
    Ferreri likes this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Accept Learn More...
    Dismiss Notice