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  1. #1
    Hi

    Does anyone have a circuit diagram to wire Limit switches in parallel with LED indication of actuation?

    Regards
    Ray

  2. #2
    As Asimov said, "Insufficient data for meaningfull answer"

    What are you plugging these here limit switches in to?

    What kind of Volts and current do we have to work with and what counts as switch closed or open?

    Do you want an LED at each switch or one for each axis on a box?

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  4. #3
    Hi

    Thanks for the reply, my apologies for the lack of substance, but in my defence, i am new to this world of CNC.

    I intend, hopefully to install "Maximum Travel" limit switches to the X,Y & Z axis of my Hobbymat Milling machine, which i am currently converting to CNC control.

    The Stepper Drivers are PM 542's and a ZP5A-INT Breakout Board, it looks like there are I/O's for 3 limit switches and a "E" stop on the Breakout board.

    It would be nice to have a separate box containing the LED's and there corresponding resistors, which obviously would give an immediate visual indication as to which switch is made.

    I understand so far that the Switch cables should be shielded, and the switches should be NC, i am not sure of the exact volts and current from the Breakout board, as the paperwork is not very user friendly.

    If possible, it would be nice to have Green LED's that turn Red when the Limits are made.

    Would i need Hard wired Limit Switches for "HOME " positioning, or leave this for Software SETTING?

    Regards.

    Ray

  5. #4
    Quote Originally Posted by manofgresley View Post
    a ZP5A-INT Breakout Board, it looks like there are I/O's for 3 limit switches and a "E" stop on the Breakout board.
    I'll have a guess then
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  6. #5
    correct me if i'm wrong as i am also new to this cnc lark still but i thought limit switches were protection to stop the machine from travelling to far.. so if they are tripped the machine would just stop at this point hence making it pretty obvious which one has tripped?

  7. #6
    Eye candy.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #7
    D.C.'s Avatar
    Lives in Birmingham, United Kingdom. Last Activity: 05-01-2016 Has been a member for 4-5 years. Has a total post count of 326. Received thanks 30 times, giving thanks to others 24 times.
    Quote Originally Posted by wilfy View Post
    correct me if i'm wrong as i am also new to this cnc lark still but i thought limit switches were protection to stop the machine from travelling to far.. so if they are tripped the machine would just stop at this point hence making it pretty obvious which one has tripped?
    Things like e-stops and limit switches are a little bit more involved then 'just stop'. Think about doing 50mph in a car and for some reason you want to stop quickly, do you cut all the power to the engine and roll to a stop or do you hit the brakes hard?

    Computers are very, very stupid so not only do you have to hit the brakes hard you need to make sure that nothing else is telling the motors to do anything else and the switches/e-stop can't be overridden by any other tech trying to ensure that the machine keeps position.

  9. #8
    Problem here is that really you want limit switches wired Normally closed and active low so if a wire breaks the signal drops, machine stops because it's no longer safe.
    Also to save inputs you'd have them wired in series. Which surely means each LED will need it's own supply to be of any use has an individual switch indicator.?

    In Mach3 Limit Home switch's can be used has home switch's if needed.
    Without limit switch's set has Home switches or individual home switches then the software can't be used to home has it doesn't now where to home too.? Instead the software just zeros out the machine coordinates where ever the gantry or moving table is rested.

    Home switches are very very useful and I'd drop limits before home switch's any day.

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  11. #9
    Quote Originally Posted by JAZZCNC View Post
    Problem here is that really you want limit switches wired Normally closed and active low

    Okay, attempt #2...
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  12. #10
    Hi Wilfy

    I agree, it should be obvious where the machine has stopped. I am a retired Mechanical Engineer. This is the first cabinet i have ever wired up on my own, so my learning curve has been near vertical, i just thought it would be a nice thing to do, as i have plenty of time on my hands, any help would be appreciated.

    Regards

    Ray

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