Australia HELP NEEDED: G540 and limit switches


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Thread: HELP NEEDED: G540 and limit switches

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    Default HELP NEEDED: G540 and limit switches

    I'm at a loss

    I’ve just done an upgrade on a new 6040 CNC which included installing a Gecko G540 (I’m running Mach3 and all axis jog OK) and have now fitted limit switches and herein lies the problem.

    I’m using the Omron micro switches from Homann in the NC configuration with -V to the NC terminal and Common back the the G540 inputs, the switches are grouped and wired in series. My understanding is/was that the axis will travel until a switch is contacted which opens the circuit, in other words the loss of current triggers a shutdown……….IS THIS CORRECT or am I missing something as the only way I can get the axis to jog is to hold the switch down into an open state and the axis stop when I release the switch which is the exact opposite of everything I thought I understood.

    Checking everything with a multimeter indicates that all wiring is OK and the switches operate as I’d expect.

    Any help will be appreciated.

    Cheers,

    ChrisO

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    Default Re: HELP NEEDED: G540 and limit switches

    Hi HiString
    Change your settings to NO for the limit and Estop.
    Think of a light switch NC is when the light is off, NO is when the Light is on.
    when movement closes the limit switch this will stop the machine.

    Cheers
    Jim Fuller



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    Default Re: HELP NEEDED: G540 and limit switches

    HiString,
    Actually, the standard configuration for Limit switches is to use the COM contact and the NC contact and wire them in series as you suggest. Then when any limit trips it opens the switch up. This help avoid situations where a broken wire might occur and you machine would never know this happened until it was too late. You normally have the input for the Limits pulled high with a resistor on the parallel port card. You configure the input pin to Active High, so when all the switches are closed not being activated there is a low going to the parallel port limit input pin. As soon as one opens that will put a high on the limit input pin and the machine will go into ESTOP.

    Russ



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    Default Re: HELP NEEDED: G540 and limit switches

    Jim and Russ,

    Many thanks for trying to help, much appreciated.

    Jim, I'd already tried the NO option without success

    Russ, I followed your suggestion but again no luck

    Unfortunately, so far Homann Designs have not returned my phone call, so, after spending the best part of two days attempting to resolve this issue I've decided to work with the NO switch configuration and wire the switches in parallel which on paper, looks as though it may be the answer.

    The fact is that our G540 when wired as per online diagrams, WILL NOT perform as one would expect, I'm more than happy to be corrected on this but have to say that to someone new to CNC, Gecko's manual is sparse while Homann's (widely referenced) wiring diagrams are exceptionally comprehensive, there is an absolute lack of information explaining the various options displayed.



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    Default Re: HELP NEEDED: G540 and limit switches

    Your wiring sounds OK.
    I have a 6040 and a G540 and my home switches are configured as NC. The COM terminal on all 3 limit switches are wired together and to ground, the NC terminals are connected to separate inputs on the G540.
    Can't comment on any Mach 3 settings as I use Linuxcnc.



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    Default Re: HELP NEEDED: G540 and limit switches

    HiString,
    Don't over complicate this issue. Keep things very simple and you will understand how things work. Think of a simple battery two wires and a light bulb. When you hook it all together the light bulb lights up. If you break a connection the light bulb loses power and turns off.

    Look at page 8 of the G540 manual it shows a diagram exactly as I described for the limit switches. Now keep in mind the parallel port card must pull the input pins high or this will not work and that is outside of the G540. You can use the diagnostic page in Mach to see if the limit inputs are changing states. Another thing to keep in mind, on the G540 they have combined the limit switch with the homing switch they are the same switch. In this case you can NOT wire these in series, each axis has its own input. That is most likely your issue.

    http://www.geckodrive.com/images/cms...8%20Manual.pdf

    Russ



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    Default Re: HELP NEEDED: G540 and limit switches

    Geoff,

    The description of your wiring appears to be the opposite of all that I've read where the NC terminals carry the -V from the power supply and the COMS go to the G540 inputs.

    Russ,

    "Think of a simple battery two wires and a light bulb. When you hook it all together the light bulb lights up. If you break a connection the light bulb loses power and turns off"

    This is how things work with a DMM connected but the minute I connect the switch circuits to the G540 it all goes down the gurgler .

    "Now keep in mind the parallel port card must pull the input pins high or this will not work and that is outside of the G540."

    Sorry mate, but this is currently beyond my understanding as the PP card is part of the M/board.

    Your comment regarding "each axis having it's own input" has me curious as I see many suggestions saying you can wire the switches in series which is what I've followed......X axis to one input and Y and Z in series to a second input.

    Guys, having dabbled in audio electronics on and off for a few decades I am finding this really frustrating.



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    Default Re: HELP NEEDED: G540 and limit switches

    HiString,
    As Crocodile Dundee says don't let all that free advise on the internet get you confused. LOL

    First you need to understand there are many ways to implement things, but they vary depending on your machine and situation. When you hear people run all their limits switches in series that is a true statement, BUT, that is a big BUT. That is only the case if you are running dedicated limit switches that will NOT serve double duty as Home Switches. If you are using HOME switches that also serve as a LIMIT switch for each axis you can NOT run these all in series. In the drawing on page 8 of the manual I posted they show the G540 implemented with Home/Limit switches. This means each axis must have a dedicated input. Why? The machine needs to know when it hits the home switch for each unique axis. Now limit switches normally come in pairs, so how do you handle that situation? Well that is a good question. A limit switch is designed to stop the CNC machine if it hit these switches to prevent damage. So on a typical axis say "X", there would be a HOME/LIMIT switch on one end and a LIMIT+X on the other end. This would be true for X and Y and in many cases users do no implement both on the Z axis because the material height is constantly changing depending on what you cut. So how do you implement something like this? This would require a dedicated input for LIMITS (+ side) mean the extreme positive limit. Then you will need an input for HomeX, HomeY, HomeZ. In this case you need four input pins. Did you notice there are four input pins on the G540? You will need to define these inputs in the CNC software Mach3 or whatever you plan on running. Now the LIMITS+ for the X and Y can be put in series and run into the dedicated LIMIT input pin. The Home switches must go into their dedicated input pins. In software the home switches need to be defined to serve both as Limit inputs and Home inputs. What happens is the CNC software only looks at the Home switches when it is running a homing routine, but at all other times those inputs are treated as LIMIT inputs, so if they trip and you are not running a homing routine the machine will go into ESTOP and everything will stop.

    Now the first step is to look at the diagnostic screen of Mach3 or whatever software you are using. You can use one of your switches wired using the COM and the NC contacts. The COM will go to GROUND and the NC contact will go to the input pin for the given Home or Limit input pin. Now just moving the switch from open to close you should see the LED on the diagnostic page change from on to off. You don't need to go any further until you can get that aspect to work.

    What the hell is this guy talking about with the parallel port inputs being pulled up? Almost all parallel ports hold the inputs high, you don't do anything to fix this unless the card does not have this feature. If it does you can disconnect everything from the parallel port and check the inputs on the diagnostic side and you will see all the input LEDs turned ON mean it sees them as high. You also need to make sure those inputs are set to ACTIVE HIGH in the cnc software.

    Russ



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    Default Re: HELP NEEDED: G540 and limit switches

    Unless you have an uber powerful machine capable of damaging itself if it runs into a hard stop then there is no real need for limit switches with Mach 3. Home switches and soft limits work just fine. I make this point due to the limited number of input pins on the G540. Run the home switches in series and go to input 1 on the G540. Define your soft limits in Mach 3 and your done. Save your other inputs for a touch probe or a tool setter or some other future need.



    Last edited by Kenny Duval; 05-03-2017 at 04:31 PM.


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    Default Re: HELP NEEDED: G540 and limit switches

    There is a lot going on here. You should always wire limit switches in the normally closed position. That way in normal operation current is running through the switches (N/C) completing the circuit.
    Then when the switch is hit it opens activating the limit function in Mach3. So you need to set Mach3 to active low input for the limit inputs.
    The reason for using N/C switches is that if a wire breaks it will set of the limit function alerting you to the fault.

    As to home switches, YES you can wire them in series or even use the same limit switches. When Mach homes, it homes 1 axis at a time so it knows which axis has hit the switch.
    The exception to this is when you have a wide gantry router with each side of the gantry driven by a separate motor.
    In this case all the home switches (and limits) can be connected in series to the one input except the home switch on the slaved axis. That way, when the gantry axis is homing it will run unit one of the home switches is hit stopping that motor. The motor on the other side of the gantry will continue until it's home switch is hit.
    This allows you to remove any racking in the axis.

    Cheers

    Peter


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    Homann Designs - http://www.homanndesigns.com


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    Default Re: HELP NEEDED: G540 and limit switches

    Have a look at this schematic

    http://www.homanndesigns.com/pdfs/EN010_V8.pdf

    In this I have the limits in series to a single input and the home switches in series to anther input.

    You could dispense with the home switches and use the limit switches as the home switches as well.

    It all depends on your machine layout and what suits you application.

    Cheers

    Peter


    Sent from my iPhone using Tapatalk

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    Homann Designs - http://www.homanndesigns.com


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    Default Re: HELP NEEDED: G540 and limit switches

    Peter.

    Many thanks for replying, although I did leave a voice message on your mobile in an attempt to sort this out prior to starting this thread .

    The fact is that the G540 we purchased will not react to any activations of switches in an NC configuration with serial connectivity based on numerous circuits available online. Today, I rewired all switches as NO in a parallel configuration and so far everything is working OK.

    As an aside, these are not home switches.



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    Default Re: HELP NEEDED: G540 and limit switches

    Are you changing the active High/Low setting in Mach 3 when moving between the NO and NC closed states?



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    Default Re: HELP NEEDED: G540 and limit switches

    Kenny,

    I had tried both Hi and Low with no success.

    Anyways, Friday morning at work and I'll be rechecking it shortly then start getting my head around Mach 3 and operating the machine.



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HELP NEEDED: G540 and limit switches

HELP NEEDED: G540 and limit switches