Problem Odd behaviour of Motor Enable Signal ??


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Thread: Odd behaviour of Motor Enable Signal ??

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    Default Odd behaviour of Motor Enable Signal ??

    Hello,
    I'm running Mach3 on a Win10 PC, outputting to an ESS and 5 Axis BOB. Everything works OK except that when the PC is turned on (after starting up the ESS), the spindle turns on, and remains on until Mach3 is started. So I thought I would use the Motor Enable signal to control the enabling of the spindle.
    The problem is that although the Motor Enable is configured to Active High, I only want it to be turned ON whilst Mach3 is running. If I press the Reset button in Mach3, the Motor Enable is turned OFF, as one would expect. If I then exit Mach3, the Motor Enable signal is turned ON, as one would NOT expect !!
    Restarting the PC I find that the Motor Enable signal seems to be persistent, and is High even before entering Mach3.
    Can anyone please explain what logic is used to control the Motor Enable signal?
    Many thanks - Kerin

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    Default Re: Odd behaviour of Motor Enable Signal ??

    Classic example of incorrect or absent E-Stop circuit.
    The E-stop should be held off until the Charge pump is active, and then the cycle start P.B. or enable P.B. is operated, picking up the E-Stop relay.
    The E-stop relay is a hard wired circuit that picks up the ready relay which in turn powers up any P.S. for servo's steppers, and the VFD or spindle/relay contactor.
    The Ready relay also advises Mach that it is active via the E-stop input pin.
    This is normally standard practice in industrial machines and commonly absent from DIY versions.
    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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    Default Re: Odd behaviour of Motor Enable Signal ??

    Hi Al, Thanks for the reply. I'm rather new to all this, so please would you be kind enough to let me know what the abbreviations P.B. and P.S. mean?
    Thanks - Kerin



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    Default Re: Odd behaviour of Motor Enable Signal ??

    P.B. Push Button.
    P.S. Power Supply.
    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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    Default Re: Odd behaviour of Motor Enable Signal ??

    Thanks Al. I sort of understand what you are saying, but am having trouble relating this to the Motor Enable output. Are you saying that the Motor Enable output is ultimately dependant on the E-Stop Input? Currently I do not have anything wired to this, and it is disabled.in the Mach3 configuration.
    I really want to know why the Motor Enable is enabled when Mach3 exits, as this doesn't make any sense to me. Is there anything I can do to keep or turn it off when Mach3 exits?
    Thanks, Kerin



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    Default Re: Odd behaviour of Motor Enable Signal ??

    I don't know the present way you have your spindle connected or controlled, but the only way that Mach has control is not until the PC has booted up and the software loaded. Until then it is purely up to some external condition that can turn on the spindle or any other device controlled by Mach, come to that.
    Therefore any motorized devices should be in a disconnected/non-powered condition.
    Often the main reason for this situation is DIY CNC is usually made up of several different hardware and software objects that are obtained from different sources, and each of these MAY have some kind of mention to E-stop that pertain to their particular component, but each have no idea what the rest of the system is made up of.
    Therefore there is no cohesive plan as to combine any or all to be controlled by one common E-stop system, as is done with a system where all component parts are put together as a package.
    Your problem is, is that the motor/spindle etc is 'live' at all times so if the controlling element (Mach) is not loaded or under control, the status of the port output pins can be at any unknown condition.
    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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    Default Re: Odd behaviour of Motor Enable Signal ??

    Thank you for the explanation, and I understand and agree with everything you say.
    The spindle is controlled by the Spindle Relay on the BOB, and the Smooth Stepper (ESS) is connected to the PC via the ethernet cable, so until Mach3 gets booted up, there should not be any ethernet comms to the ESS. I don't see why the spindle turns on when powered up.
    Therefore I think I perhaps should address this problem to the ESS forum instead.
    Many thanks for your help
    Kerin



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    Default Re: Odd behaviour of Motor Enable Signal ??

    Part of your problem is that the Motor Enable pins are not really very useful. very often you are best off ignoring them.
    I suggest you use a charge pump circuit, and you must use an eStop circuit, and you need to sort out your Active Highs from your Active Lows.

    As to exactly why the spindle comes on before Mach is fired up: that is probably because the output port which is meant to control the spindle has a pull-up resistor on it so it gives out a HI signal (which turns the spindle on) until Mach and the ESS get sorted out. You need to invert some of your logic levels. You will probably need to use a logic LO to turn on the spindle. Yes, it can be confusing! Sit down with pencil & paper and draw out the signal flow and mark what is happening.

    Cheers
    Roger



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    Default Re: Odd behaviour of Motor Enable Signal ??

    The bottom line is the AC power for all motors should not be on before Mach boots and ONLY come on when the E-stop is manually energized, as per recommended 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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    Default Re: Odd behaviour of Motor Enable Signal ??

    Thanks Al and Roger,
    On the Warp9 forum I discovered that the reason the spindle turns on before Mach3 starts, is because the pull down resistor on the ESS card outputs is bigger than the pull up resistor on the inputs of the BOB card, so the pull up wins the battle and the input is seen as HIGH by the BOB, hence the Spindle Relay turns on. Short of hacking the BOB card, there is little I can do about this, and it can't be corrected by changing signal states.

    My solution therefore is:-
    I have a latching emergency switch which shuts off power to the motor drivers, and I usually leave this off until Mach3 starts, and I then I turn it off again when Mach3 exits. I can use the presence/absence of power on the drivers to turn a relay on/off which can thus enable/disable power to the spindle. Although not ideal, I can work with this.
    Many thanks for all your help.
    Kerin



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    Default Re: Odd behaviour of Motor Enable Signal ??

    Quote Originally Posted by Al_The_Man View Post
    Classic example of incorrect or absent E-Stop circuit.
    The E-stop should be held off until the Charge pump is active, and then the cycle start P.B. or enable P.B. is operated, picking up the E-Stop relay.
    The E-stop relay is a hard wired circuit that picks up the ready relay which in turn powers up any P.S. for servo's steppers, and the VFD or spindle/relay contactor.
    The Ready relay also advises Mach that it is active via the E-stop input pin.
    This is normally standard practice in industrial machines and commonly absent from DIY versions.
    Al.
    Vg

    Andrew

    Andrew


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Odd behaviour of Motor Enable Signal ??
Odd behaviour of Motor Enable Signal ??