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  1. #13
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    Default Re: E-Stop Wiring?

    Quote Originally Posted by purple_jeep View Post
    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
    Just a suggestion, having a contactor between power supply and drives will allow drives to run until the capacitors in the power supply drain. This could be up to a couple of seconds or more depending on the system. Alot of damage can occur while waiting for this to happen. Would be nice for estop button to instantly disable drives without relying on contol software if possible.

    Edit: I meant to say having a contactor between power supply and transformer like the origional poster said.

    Last edited by mmurray70; 01-21-2017 at 10:54 PM.


  2. #14
    Community Moderator Al_The_Man's Avatar
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    Default Re: E-Stop Wiring?

    Never seen that in practice, but the enable input to the drives could be activated at the same time if it is a concern.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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  3. #15
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    Default Re: E-Stop Wiring?

    I probably went overkill on the power supply on my first cnc project, a little taig mill. That thing would run for maybe 2-3 seconds after cutting power.

    My last project was a Fadal VMC 4020 and this problem wasnt as bad but was definitely very noticable even on this machine. At one point i had it setup to simply cut power to power supply and an axis would run on considerably after. Especially noticeable if the axis was already up to speed in a rapid. I changed things so Estop disables drives and it stops right away now.



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    Default Re: E-Stop Wiring?

    On this system the power supply has the enable the individual drives do not (Allen Bradly 1389 chassis system). Also the power supply has a shunt resistor which I believe discharges the output on e stop.

    Cheers

    Chris



  5. #17
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    Default Re: E-Stop Wiring?

    A complete estop circuit.

    E-Stop Wiring?-charge-pump-estop-jpg
    This has watchdog signal fed into bottom left hand corner, marked CPUMP
    Note that the left hand side of the circuit, is 5v and is 100% isolated from the right hand side by the 5v relay.

    ESTOP is just that for EMERGENCIES - remove power. Not for normal stop as the next poster points out.
    An added feature to the above is an adjustable timer module to remove power a short time after estop.
    The there are the issues of a Z axis sagging under its own weight, needing a spring applied break.

    I was just trying to give a still fairly simple, safe way to do estop circuit. This at least handles the case of a control cable being unplugged.
    There are still other issues, like the CPU detect whether this safety circuit is healthy... The list goes on.


    Attached Thumbnails Attached Thumbnails E-Stop Wiring?-charge-pump-estop-jpg  
    Last edited by neilw20; 01-22-2017 at 05:08 PM.
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.


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    Default Re: E-Stop Wiring?

    Quote Originally Posted by purple_jeep View Post
    On this system the power supply has the enable the individual drives do not (Allen Bradly 1389 chassis system). Also the power supply has a shunt resistor which I believe discharges the output on e stop.

    Cheers

    Chris
    Before you end up with even more random suggestions, can you tell us a bit more about the drives?
    Like how does the power supply, and power enable work. Are there any other inputs for enable/stop/whatever?

    With most servo systems, you ideally don't want to remove power immediately, but instead you want it to remain active for a second or two, so the drive remains powered until motion comes to a complete stop. Cutting power before motion stops, can lead to the drive faulting out, or simply disabling, allowing the servos to freewheel to a halt. There are delay relays available for this exact purpose.
    Most modern drives will usually have a Stop input, which is what you would normally use for an E-stop, as the input simply tells the drive to halt all motion, after which you can remove power. Do your drives have this ability?

    Before activating the drives, you want them to be controlled before they get enabled I.e. you want the KFlop/Kanalog ready to control them prior to being enabled, otherwise they will drift.

    The specifics of how you implement the above varies slightly depending on drive features/capability.



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