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  1. #11
    I think I'm starting to get this.

    JAZZCNC I've tried to map out what you've described in the PDF below. I've also attached the CNCRP diagram of where the relevant switches are located on the machine.

    S1, S2 and S3 on my machine seem to relate to S1 - Y, S2 - X, S3 - X prime home. I've tried to match these up with Home 1, 2, 3 and Limit 1, 2 in the diagram. Hopefully you can offer some guidance if I've got the order wrong.

    Mapping these back to the pins in the control box this leave S1 unallocated which doesn't seem right.

    Would this setup eliminate the need for the mechanical e/stops I have or do I still need those on each axis? I would rather get rid of them if I could.

    Thanks
    Attached Thumbnails Attached Thumbnails PROXIMITY.pdf   Click image for larger version. 

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  2. #12
    Quote Originally Posted by irving2008 View Post
    Never thought about this before, but if you are using parallel connected HOME switches you MUST configure Mach3 to back off them (unless that's the default) else it'll never home the 2nd and subsequent axis as it'll never see the switch state change.
    Yes that's how Mach works Irving Hits the switch then backs off then Zero's the Axis before moving onto next axis.


    Quote Originally Posted by irving2008 View Post
    Also, series connected NC surely only works with the 2-wire versions.
    For Limits ONLY then Series wired Prox switches work just they have slower reaction times with each switch but for the few needed, esp if like me you use traveling switches that look for a target so only 1 each axis then it's not a problem.
    The Link Eddy gave explains about series wired prox switches.!! Sensors - Outputs & Wiring

  3. #13
    Quote Originally Posted by davrich View Post
    Mapping these back to the pins in the control box this leave S1 unallocated which doesn't seem right.
    Ok Well first of all under stand that you have 4 spare Inputs labelled S1-S4 and can use any you like for anything you like. In this case you have assigned S2 for Limits and S3 for homes. Could easily be S1 limits and S2 home doesn't matter so long has you Set the correct Pins inside Mach3 inputs. ie: S1 = pin2 so set Limit's ++ and Limits-- to pin 2.



    Quote Originally Posted by davrich View Post
    S1, S2 and S3 on my machine seem to relate to S1 - Y, S2 - X, S3 - X prime home. I've tried to match these up with Home 1, 2, 3 and Limit 1, 2 in the diagram. Hopefully you can offer some guidance if I've got the order wrong.
    Now this is were it changes regards Homing because you have 2 switches Homing one Axis to square the gantry.
    So now you need to have the Second Switch (Home2) on X using it's own Input. The other switch(home Prime) can still be wired in parallel with the Y and Z axis so share same Input.

    Now you wire it just the same regards Brown and Blue but will need an extra wire for the (home 2) signal (black) which will go back to it's own input.

    So now you will have connections on the control will go.

    All Limits = S1
    HOME X(prime) Y & Z = S2
    HOME X(Home1) = S3

    Quote Originally Posted by davrich View Post
    Would this setup eliminate the need for the mechanical e/stops I have or do I still need those on each axis? I would rather get rid of them if I could.
    Not sure what your meaning here about Mechanical E-stop.?

    E-stop should be a Button that gets pressed and SHOULDN'T be removed under any circumstances. It should also be wired and setup in such away that it doesn't just send signals to the control software, like your doing in this instance with limits.

    The E-stop should remove power to any devices that are relavant Ie drives, Vfd, spindle etc and then inform the control software an E-stop has happened. Often this is done thru the use of relays with low voltage controlling high voltage devices but this is a whole new area which I won't get into now. Just search the forum to find out more.

    BUT what I will say is DONT REMOVE THE E-STOP and DONT rely on SOFTWARE controlled E-STOP.!!
    Last edited by JAZZCNC; 17-01-2014 at 08:09 PM.

  4. #14
    I decided to upgrade my cheap proximity switches and makeshift wiring for some Pepperl & Fuchs ones.

    Seemed like a good idea, until now!

    The ones Iíve bought are PNP https://www.pepperl-fuchs.com/global...ils&prodid=514.

    Iíve hooked them all up and they light up when metal is placed in front of them.

    Problem is, in Mach 3 th fact that the switch is tripped doesnít register.

    When I add my old Chinese cheap switch, it works fine.

    Seems that the issue is that my old ones were NPN and the new ones are PNP.

    can anyone tell me whether this is easily fixable by some tweaks to the wiring or am I better off just getting NPN sensors?

    If any more information is needed to answer the question Iíll fill the gaps.

    Thanks in advance

  5. #15
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 4-5 years. Has a total post count of 304. Received thanks 35 times, giving thanks to others 10 times.
    Quote Originally Posted by davrich View Post
    I decided to upgrade my cheap proximity switches and makeshift wiring for some Pepperl & Fuchs ones.

    Seemed like a good idea, until now!

    The ones I’ve bought are PNP https://www.pepperl-fuchs.com/global...ils&prodid=514.

    I’ve hooked them all up and they light up when metal is placed in front of them.

    Problem is, in Mach 3 th fact that the switch is tripped doesn’t register.

    When I add my old Chinese cheap switch, it works fine.

    Seems that the issue is that my old ones were NPN and the new ones are PNP.

    can anyone tell me whether this is easily fixable by some tweaks to the wiring or am I better off just getting NPN sensors?

    If any more information is needed to answer the question I’ll fill the gaps.

    Thanks in advance
    Sorry in a late reply to this - only found this thread by looking for information on inductive sensors.

    For 3-wire sensors:-

    NPN are low-side switching, so the sensor goes low impedance to ground in the presence of metal. PNP are high-side switching, so the sensor goes low impedance to supply-voltage in the presence of metal.

    This has a bearing on how you wire these to your BoB, or whatever (for now, "BoB"). If the BoB's inputs are opto-coupled AND it presents both anode and cathode of the optocoupler input then you have a lot of flexibility, and either NPN or PNP can be made to work. For an NPN you'd connect the sensor output to the cathode of the optoisolator, and wire the anode to +5V (or +12V through a current limiting resistor). For a PNP, you'd wire the sensor output to the anode, and the cathode to ground (and if the sensor is powered by 12V, then probably have to include a current limiting resistor as well). More typically the BoBs (at least the couple I've come across) have the anodes of the optocouplers bonded to their own local 5V supply and you have to have low-side (i.e. NPN) switching - hence the NPN being the sensor of choice.

    If you're stuck with PNPs and a low-side switching BoB, you *could* frig it a couple of ways. One to include a NPN transistor that is switched from the sensor output from the PNP - very easy, costs pennies and easily knocked up on strip board. Or, you *could* use the high-side switch to reverse-bias the LED in the optoisolator (it's naughty, but can be done) - connect the sensor output via a 470R resistor to the BoB input, connect a 220R resistor to ground (this allows the PNP to pull the cathode voltage up to reverse bias the optoisolator). In theory the cathode would sit around 4V with the PNP sensor "ON" and that's enough to stop the LED in the optoisolator illuminating. The only problem with this method is On is Off, and vice versa, that you have to invert the input in Mach3. You might have to play with the value of the 2 resistors, but keep the ratio the same (the series resistor from the sensor output having about twice the resistance of the external resistor from the BoB input to ground).

    Something like

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    (Note: I've not tried this, but it ought to work)

    One word of warning - if you removed the pull-down resistor, or disconnected the 0V to it, you're going to exceed the max reverse voltage on the optoisolator and destroy that input. Either don't do this!, or place a diode - anode on the BoB input, cathode to the BoB's 5V supply to clamp the input voltage to not much more than 5V
    Last edited by Doddy; 18-02-2018 at 01:39 PM.

  6. #16
    prompted by seeing Doddy's reply

    I have 2 questions

    1)
    which BOB are you using ?
    it could be one I have reverse engineered or
    the BOB's circuit diagram available online

    2)
    what is the DC supply voltage you intend to power the
    normally open PNP proximity switches ?

    John
    Last edited by john swift; 18-02-2018 at 05:34 PM.

  7. #17
    Thanks for all replies on this.

    Sorry, I didnt receive notifications that anyone had responded, so will check my preferences.

    I ended up buying some NPN ones, so will be selling the others on.

    Thanks again

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