G540 E-Stop


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  1. #1
    Member kolias's Avatar
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    Default G540 E-Stop

    I’m looking at a wiring schematic for the G540 and besides the enable switch which is connected on pin 10 there is an E-Stop on the AC line feeding the switching power supply unit.

    I remember reading somewhere that it is not a good practice to cut the AC power on stepper motors.

    So where do you put the E-Stop?

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    Nicolas


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    Member john-100's Avatar
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    Hi Nicolas ,

    the problem is if you disconnect the DC supply to the G540

    the E stop in the AC supply to the power supply
    is just another on/off switch thats easier to switch off in a panic

    the E switch connected to the PC will stop the stepper motors quicker
    provided the PC is still responding

    but the E stop in the mains supply is guaranteed to stop every thing
    once the stored energy in the power supplies has been used up

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

    John



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    Member kolias's Avatar
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    Thank you John for the info, I do have this wiring schematic, very nice work,

    So now how do I calculate the fuse size on SW-06? My DC power supply will be 36V / 10A and the AC line in Canada is 120V. (I just happen to have the 36V/10A switching power supply unit and I will use it for now and perhaps later I will get a 48VDC / 10A unit)

    Nicolas


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    Member john-100's Avatar
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    Hi Nicolas ,

    I would of expected the fuse rating to be printed onto the power supply

    but with an output of 36V at 10A = 360w
    excluding any losses you need a mains input of 120V at 3A

    if due to losses within the power supply the output is only 80% of the input you will need a 4A fuse
    its possible due to the switch on surge current
    you may have to use a 5A fuse

    HRC ceramic fuses are best as they stay in one piece even with
    very high fault currents

    John

    PS had a quick search and it looks like you need a 6.5A fuse
    the surge current is larger than I first expected

    http://www.ebay.co.uk/itm/36V-10A-36...item2c64e26854

    Last edited by john-100; 05-17-2012 at 04:57 PM. Reason: add PS and link


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    Community Moderator Al_The_Man's Avatar
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    You may also want to check in the P.S. itself, many are fitted with an on board fuse in the L1 conductor.
    If you have any other 120v loads in parallel you would have to fuse accordingly.
    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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    Member john-100's Avatar
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    Hi Al

    good point about additional loads

    I overlooked the spindle motor

    the largest fuse you can for an IEC connector is 10A

    once the stepper motor supply has been switched on
    you have about 6A available for the spindle motor and its speed controller etc

    with a soft start , and a 120V supply , that probably limits you to a
    500/550W motor
    thats if you don't use a separate mains supply for the spindle

    John



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    Member kolias's Avatar
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    Sorry kind of complicated for me, electricity is not my strong field…

    Never used my 36DCV /10A unit and don’t know if it has an internal fuse. All it is written on the unit is:
    MW, S-350-36, 115VAC 6.5A 230VAC 4.0A, 50/60HZ. The DC Voltage is adjustable but never try to see by how much.

    This unit will not feed the spindle because I plan to have a Hitachi X200 VFD. My 4 steppe motors are STP-MTR-23079, 276oz.in, 2.8A, 3.82mH, 1.10 ohms and I don’t plan to feed anything else from this power supply.

    So a 5.0A fuse will be sufficient on the AC line?

    BTW what kind of connector is the IEC?

    Nicolas


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    Community Moderator Al_The_Man's Avatar
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    IEC Connectors - Full range of quality mains rated inlets, outlets and connectors with electrical ratings upto 20A 250V by Bulgin Components
    How do you intend to E-stop the spindle?
    One of the ideal E-stop circuits is to have all the N.C. E-stop functions in one low voltage sourced string with the end result as a small control relay of which on contact will cut the AC power to power relays or contactor(s) that cut power to the coil voltage.
    This relay would also advise Mach or other controller that a E-stop had taken place.
    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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    Member kolias's Avatar
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    Al, I don’t know yet how to E-stop the spindle and the purpose of this post is to get ideas on how other members achieve this function.

    One way is like what John said on post #2 with the schematic from homanndesigns. This schematic has a VFD connector which will send a signal to VFD to cut the power (I think) and therefore stop the spindle and let Mach3 know about it. Since I don’t know enough about electronics, I must understand and feel comfortable with a schematic before I proceed and that is another reason I started this post

    Nicolas


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    Member kolias's Avatar
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    Can someone help me understand the homanndesigns wiring schematic from post #2 ?

    The way I read it, the AC line comes in at the IEC Plug on SW-06. From this switch we go the the 48V power supply unit plus to the IEC Female Socket and from this socket to RL-04

    I see that SW-06 is a double pole switch. Can this switch be a regular household switch? Why it has to be double pole?

    Why I can’t wire directly to the RL-04 from SW-06 ?.

    What is the purpose of RL-04 ?

    Regarding the Enable Switch to pin 10, is this a regular on/off switch or an E-Stop switch?

    Nicolas


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    Member john-100's Avatar
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    Hi Nicolas ,

    the enable switch to the G540 terminal 10 is used by many people
    as the E stop switch
    IF the PC is responding correctly
    Mach 3 software will stop sending step signals and
    switch off relay RL-04 to remove the mains supply to any thing connected to the IEC socket
    ( no good if a spindle motor or the psu is emitting smoke signals )

    in my case it will be for Mach 3 to switch the spindle motors speed controller on and off
    when I convert a mini lathe to CNC
    but I'd go for the E stop switch directly controlling the mains supply
    and not via the PC

    if you don't have a E stop switch with the correct switches
    to safely switch the mains supply to the motors
    and via the G540's terminal 10 an E stop to Mach 3
    as Al suggested you can use a relay / contactor
    to keep the safe low voltage circuits and the mains separate

    the choice of E stop you use will depend on the damage that can be done to you and the machine when things go wrong

    as for sw-06 being a double pole switch
    a double pole switch ensures the machine is isolated from the mains supply
    it disconnects the live supply even if the mains wiring is crossed
    as can happen with a non polarised mains plug
    the choice of switch for the G540 enable (terminal 10)
    depends on how you want to use it


    John

    Last edited by john-100; 05-18-2012 at 05:25 PM.


  12. #12
    Member kolias's Avatar
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    Thank you John for the help

    If I understand correctly the homanndesigns schematic has 2 E-stops, one (the Enable) is providing a stop function to the motors through Mach3 and is required for the G540 to function properly.

    The other E-stop is SW-01 which is cutting the AC power to the 48V unit. So with these two E-stops I will assume that I have a good protection.

    Sorry but I don’t understand what Al said on post #8. What is a relay / contactor?
    and how you can keep separate the low voltage circuits and the mains?

    Nicolas


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