E-Stop Wiring?


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    Default E-Stop Wiring?

    HI All,

    Quick question about best way to wire up e-stop. Currently I have an estop chain consisting of Estop Buttons, Thermal switches on motors, Kanalog Watchdog. When these are all met it energizes the contactor supplying power to the Servo motors, spindle drive etc.

    The issue I have is until Mach is up and enabled the servo's drift as the axis are not enabled. I am thinking of using one of the axis enable outputs from Mach/Kanalog as another condition in the estop chain. I already use the Zaxis enable output to drive a brake on the Z axis so I would have to use either the x or y (or both).

    This does not seem quite right, is there a way to get a general e-stop output from Mach (like when you press ESC or press the reset button on screen?).

    Any other e-stop suggestions.

    Cheers

    Chris

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    Community Moderator Al_The_Man's Avatar
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    Default Re: E-Stop Wiring?

    There is the proper accepted way with a E-stop/system start relay, this is responsible for disabling/removing power from all motive power devices.
    Also it advises the controller (e.g. Mach) that an E-stop has taken place or in effect.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    Default Re: E-Stop Wiring?

    The way I was advised to do e-stop/enable circuits, was the E-stop circuit should be an entirely stand alone circuit, which ultimately removes power in a safe controlled way, so in the event the controller locked up, motion would still stop.

    Then you have a separate software controlled enable circuit, which enables the drives.

    And to avoid any problems with software fighting against hardware, you keep them separate. The controller does take an input from the E-stop circuit, so it knows if an E-stop has occurred, however it has no control over that circuit.



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    Community Moderator Al_The_Man's Avatar
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    Default Re: E-Stop Wiring?

    That is pretty much it, although there is a couple of additions can be made to the series E-Stop string as is done with just about all commercial CNC.
    That is to use a contact on the control relay to advise the controller that an E-Stop has taken place and also if the Controller itself is either off or not yet booted up, an output can be inserted in the string to hold off the E-stop relay until the control is ready, this would be the use of the charge pump on a Mach system.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    Default Re: E-Stop Wiring?

    Al, that's what the Kanalog Watchdog signal is that purplejeep/Chris mentions. During booting the Kanalog outputs are in an unknown state, so there's a FET output that only goes high once the Kanalog is fully powered and has been initialised by the KFlop.



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    Default Re: E-Stop Wiring?

    Quote Originally Posted by Al_The_Man View Post
    There is the proper accepted way with a E-stop/system start relay, this is responsible for disabling/removing power from all motive power devices.
    Also it advises the controller (e.g. Mach) that an E-stop has taken place or in effect.
    Al.
    This is almost exactly what I have using a 3 phase contactor between the isolation transformer and the Drives power supply. Aux contacts on this contactor feed a control signal back to Mach to indicate an Estop has occurred.

    I do use the Kanalog watchdog and I guess what I am after is the Mach 3 charge pump signal equivalent from the Kanalog board to indicate Mach is up and operating. Does the chargepump signal drop when a software Estop is triggered in Mach 3 (either by hitting the ESC key or clicking on the reset button)?

    Cheers

    Chris



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    Default Re: E-Stop Wiring?

    IIRC the Mach charge pump is on once the system has booted and loaded Mach, then stays on unless a PC system crash etc.
    If Kanalog has a similar function as the charge pump, it could be incorporated into the E-stop string where all sensors, switches, etc are all NAND'ed together.
    If you are getting servo drift before the system is enabled then they are not being controlled by the E. string.
    Ideally the power to the drives should be held off with the control E relay etc, but a bare minimum should be a drive disable input etc.
    Al..


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    Default Re: E-Stop Wiring?

    I've just remember that Mach provides enable outputs. What you want to do is map one of those to a KFlop/Konnect output that controls the drive enables.

    If you were to map it to something that controlled the E-stop circuit, you'd get a race situation, because Mach wouldn't enable as the E-stop circuit was triggered, and you couldn't un-trigger the circuit because mach hadn't enabled it.



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    Default Re: E-Stop Wiring?

    Problem is although both Mach and Kanalog are both up (watchdog is active) Mach is in reset on startup which leaves the drives disabled in Kanalog. This means that the axis have power as Kanalog is active but not controlling the outputs because of Mach 3's status thus allowing axis drift.

    Need a good way to determine Mach 3 status and use that as part of the Estop chain, I can use one of the axis enable signals I am just wondering if there was a better way.

    Cheers

    Chris



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    Default Re: E-Stop Wiring?

    Quote Originally Posted by m_c View Post
    I've just remember that Mach provides enable outputs. What you want to do is map one of those to a KFlop/Konnect output that controls the drive enables.

    If you were to map it to something that controlled the E-stop circuit, you'd get a race situation, because Mach wouldn't enable as the E-stop circuit was triggered, and you couldn't un-trigger the circuit because mach hadn't enabled it.
    This is what i will do I guess, already using the zaxis enable to run a brake on that axis just wondered if there was a more system level output I could use instead of one mapped to a specific axis.

    Cheers

    Chris



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    Default Re: E-Stop Wiring?

    Mach 3 doesn't provide axis specific enables, it simply provides 6 enable signals that you can map to whatever port/pin you want.



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    Default Re: E-Stop Wiring?

    If I was a user of Mach, I would re-write a screen that did not have the on-screen E-stop button, it does not conform to typical CNC machine practice.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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