G540 E-Stop


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Thread: G540 E-Stop

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    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?

    Similar Threads:
    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.


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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


  13. #13
    Member john-100's Avatar
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    Hi Nicolas ,

    a contactor is basically a very heavy duty relay

    for example , a single contactor is found in single phase and 3 phase
    Direct On Line starters that are able to connect a 10HP motor to a
    440V 3 phase supply (UK)
    with 3 pairs of normally open high current contacts to power the motor
    and a a pair of low current N/O contacts for the control circuit

    (over 10HP the motors are started in star connection then after a delay switched to delta using 3 contactors controlled by timers
    or in new installations controlled by an electronic soft start control)

    the low current N/O contact maintains the supply to the coil once the
    start button has been pressed , until the normally closed stop switch is pressed (or when fitted an motor overload switch opens )
    E stop switches can be wired in series with the DOL starters stop switch
    (the coil voltage being 240V or 440V for UK single or 3 phase supplies)

    24V , 50V or 110V coils are available for low voltage control circuits
    24V being ideal for new machines with programmable logic controllers


    if you used a relay or contactor as in Al's post
    your E stop circuit can be powered by a low voltage supply

    this is safer as it avoids having both mains and low voltage wires to the G540 connected to the separate parts of the same E stop switch


    you could put the low voltage controls in one box
    and power supplies and switch gear connected to the mains in another box
    ( or divide a large box into two parts)

    John



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    Member kolias's Avatar
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    I like the idea of having the low voltage controls separate from the power supplies and I will do that.

    I could have a 24V supply for the E-stop circuit but I don’t understand how this will work. Are you saying to have a new relay powered by 24V and this relay to control the RL-04 and SW-01?

    Is it possible to explain with a simple schematic how this can be done?

    Nicolas


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    Community Moderator Al_The_Man's Avatar
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    Here is one example from a old project, if you notice, the control relay ERL has a 24vdc coil and is responsible for switching any 120v or 24v power devices that are required to be off in a an E-stop condition, check the occurrences of ERL contact, you may not need that many, the E-stop string itself only shows a couple of actuators (P.B's) but in fact can have as many actuators you wish in series that would need to initiate an E-stop, such as N.C. limit switches or watch dog timers etc, in the case of Mach type controls, an auxiliary contact on ERL could be set up as the E-stop input into Mach to advise an E-stop has taken place.
    If you bring the main power to the system through two AC conductors then it is much easier to switch and control one AC power source rather than everything plugged into separate receptacles.
    The circuit also show the push maintained type buttons, but the method mentioned by John is preferred where there is a N.O. start PB and you would need a N.O. contact on ERL in parallel with the PB to retain it.
    Al.

    Attached Thumbnails Attached Thumbnails G540 E-Stop-control1-pdf   G540 E-Stop-controlexample-pdf  
    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 Nicolas ,

    in the Homann design circuit the E stop switch controlles the 48V power supply for the G540 and the 48V relays

    the simple solution would be for you to use 36V relays instead
    but I've not found 36V versions of the 48V relay from Homann Designes
    Farnell sell a 24V version that you could use either by connecting a 270 ohm 1W resistor (approx half the coil resistance , 576/2=288)
    in series with the coil or using an additional 24V DC power supply for the relays (24V at 42 mA per relay is enough)

    Power - General Purpose | Farnell United Kingdom

    search for flange mounting relays ,then go to page 3
    (not sure why the long link to the page didn't work)

    the next question is do you want the E stop switch to connect the G540
    enable input to GND

    the SW-01 E stop switch on the diagram has one N/O contact and one N/C contact
    but the smaller DPDT SW-05 E stop switch from Homann Designes
    can be wired as two normally closed contacts
    one for the G540 enable and the other to switch on a 24V relay controlling the mains supply to the G540 power supply

    John

    Attached Thumbnails Attached Thumbnails G540 E-Stop-g540-relays-jpg  
    Last edited by john-100; 05-19-2012 at 02:23 PM. Reason: correct error on the diagram -G540 GND terminal


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    Member kolias's Avatar
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    Lots of information in the last two post, thank you both

    I have printed the PDF files and I have to study them to understand well.

    Along with my order from Soigeneris I also have three 24V relays coming and perhaps they will be suitable for what I want to do.

    Sorry but I don’t know what will happen if “do you want the E stop switch to connect the G540 enable input to GND”.

    I like the idea of the SW-05 E-stop with the two NC contacts but I don’t know how practical this will be because by pressing this switch the power to G540 and the AC line will go OFF meaning that everything will go dead.

    On my previous two cnc I had only one E stop which was only telling Mach3 to stop the motors. I found this set up was convenient but perhaps not safe.

    Bottom line is that I think the HomannDesign schematic is what I would prefer; the enable switch will only stop the G540 (and I guess the motors) and for a real emergency SW-01 will cut the AC power to everything. Is this considered a good strategy?

    Nicolas


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    Hi Nicolas ,

    as I understand it
    the G540 sends an E stop signal to the mach 3 software
    when the stop switch connecting terminals 12 & 10 goes open circuit
    or the 12Khz charge pump signal is missing

    all outputs are switches off by the G540's E stop and charge pump detector circuit.
    the stepper motors free wheel , the relays connected to outputs 1 & 2 switch off and the 0 to 10V control voltage to the spindle motor speed control is set to zero

    I'm not sure why you think switching off the mains power and signaling an
    E stop to the G540 with the same switch could be a problem

    but when building your own machine, there is no reason why you can't use two switches if you prefer it that way


    John



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    Member kolias's Avatar
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    Quote Originally Posted by john_100 View Post
    Hi Nicolas ,

    I'm not sure why you think switching off the mains power and signaling an
    E stop to the G540 with the same switch could be a problem

    John

    Because I don't really know what happens when you switch off the mains power; do I have to re start Mach3 (doing so I may loose any parameters I was working with before).

    Actually I like the idea of using one switch but as I explained before if Mach3 goes off too, I would not like that

    Nicolas


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    Member john-100's Avatar
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    Hi Nicolas ,

    I think I know what your concerned about now
    I've not been able to test Mach 3 my self, I've a few more parts to collect first

    with your previous machines E-stop circuit , just using the G540 enable input
    I assume you have to home the machine after an E-stop any way
    with the stepper motors free wheeling I'd expect any axis moving at speed to
    have lost its position

    with the PC plugged into its own mains supply
    the new E-stop circuit switching off the power to the G540 should not
    make any difference to Mach 3

    John



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