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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Baffled with Limit & Home switches and BOB
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  1. #1
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    Jul 2008
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    267

    Baffled with Limit & Home switches and BOB

    I have read all about limit and home switches. I realize Mach3 can use limit for home switches and this is preferred. But I am still somewhat confused.

    Here is what I want to do:

    (1) I want to use my limit switches as home switches

    (2) I want my limit switches NC, so if a wire breaks, the machine will stop.

    I have a Bob Campbell breakout board. It has connections for separate X, Y & Z limit switches and separate X, Y & Z home switches.

    I have mounted switches for X+ and X-, Y+ and Y- and use a single switch for Z (for both Z- and Z+)

    So here is my guess as how I put this all together:

    (1) X+ and X- are wired NC in series and connected to the X limit connector on the BOB (ground and signal).

    (2) Y+ and Y- are wired NC in series and connected to the Y limit connector on the BOB (ground and signal).

    (3) Z is wired NC and connected to the Z limit connector on the BOB (ground and signal).

    (4) I dont even use the home connectors on the BOB.

    (5) In Mach I set the appropriate ports and pins, and set them to Active High.

    Is this OK?

  2. #2
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    Aug 2008
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    1162
    Yes, that will basically work. However, as I recall I had to also enable auto limit override on the Mach settings screen so that homing wouldn't cause an e-stop.

  3. #3
    Gold Member
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    May 2005
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    1810
    Personally - I don't like the idea of using the limits as the home switches. What's your motivation for doing this?

    Scott
    Consistency is a good thing....unless you're consistently an idiot.

  4. #4
    Gold Member
    Join Date
    Mar 2004
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    1798
    mxtras,
    I don't know about anybody else, but I wanted to use the same switch due to the real estate required for multiple switches on my mill drill! On each of the X and Y axis, I have used only one switch each and it handles both the limits and home function for each one!
    In addition, it save I/O on the BOB and parallel port. Matter of fact my controller will also tell me which axis tripped on limit and of course if your using only one pin for all limits, this is not possible.

    As stated though, the main reason was real estate requirements on my Mill/Drill!
    Art
    AKA Country Bubba (Older Than Dirt)

  5. #5
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    Jul 2008
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    267
    Thanks for the replies gang, sounds like I am on the right track.

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