E-stop wiring, which way is correct?


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    Default E-stop wiring, which way is correct?

    I know this has probably been beaten to death but I haven't been able to find a solid answer.
    I am building a hobby CNC of my own design and am working on the electronics, using an Ethernet Smoothstepper, CNC4PC C25 Breakout Board, DM542T stepper drivers, and a Makita RT0701C router as the spindle.

    I can think of at least 3 ways to wire the e-stop, and there are probably many more. I'm looking for feedback on which way is the most correct, or if there are changes to the diagrams below that need to be made?

    The diagrams are only a snippet to convey how to wire the e-stop.

    I've seen other diagrams that put the e-stop in series with limit switches.
    I should also note that my stepper drivers have ENABLE pins and I am not currently using them.

    Option 1: Probably the most direct way to handle it, but might cause noise.
    E-stop wiring, which way is correct?-estop-option-1-jpg

    Option 2: Mostly the same as #1 but uses a relay instead of directly cutting power. Probably less noisy.
    E-stop wiring, which way is correct?-estop-option-2-jpg

    Option 3: This is what I see in most hobbyist CNC videos, but I believe it to be the least-safe method.
    E-stop wiring, which way is correct?-estop-option-3-jpg

    Similar Threads:
    Attached Thumbnails Attached Thumbnails E-stop wiring, which way is correct?-estop-option-1-jpg   E-stop wiring, which way is correct?-estop-option-2-jpg   E-stop wiring, which way is correct?-estop-option-3-jpg  
    Last edited by secretspy; 09-12-2018 at 05:12 PM.


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    Member john-100's Avatar
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    Default Re: E-stop wiring, which way is correct?

    Options 1 & 2 would be better with an E-stop switch with two N/C contacts -

    the problem is you will need to buy an E-stop switch unit that you can buy replacable switch blocks for
    if you can not buy one fitted with two sets of N/C switches

    all the low cost Chinese E-stop switches I have seen have 1 N/C & 1 N/C contact

    and for option3
    I would connect the N/C contact to the breakout board
    using the N/O contact, the electronics would not see an E-stop if a wire became disconnected

    John



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    Default Re: E-stop wiring, which way is correct?

    Like John said:

    Using a E-Stop directly to the BOB is enought. Use NC (Normal Close). Because is the wire gets disconnect, the BOB will Stop.
    When you press E-Stop, Mach3 will get the signal and STOP everything.

    If you break VAC line, it's enought to stop the machine and you don't need to send a signal to the BOB. I understand what you want.

    I have machines with two systems... my first machine I did not know how to configure mach3 and I make the E-Stop just BREAK VAC 127V line.

    Today I make:
    E-Stop just sending a sigtal to BOB / Mach3 --- using NC signal.
    and side-by-side of E-Stop button I use a ON/OFF switch to energize my drivers...

    By the way, I have never got any problem of having my PC freezing and NOT stopping when pushing E-Stop button. But IF i have, I would turn off immediately on/off switch.

    Parallel DB25 interfaces is very good and in my opinion E-Stop is enough.
    If you use USB board take care, because there is a delay and some bugs... maybe it's a good idea breaking VAC line.



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    Default Re: E-stop wiring, which way is correct?

    Thank you both for the replies. So it sounds like option 3, except using the NC contact, is enough? I think if I were using an old PC with a parallel port (instead of the external smoothstepper) I would be more concerned about breaking the AC line.

    Quote Originally Posted by cebaldocchi View Post
    If you break VAC line, it's enought to stop the machine and you don't need to send a signal to the BOB. I understand what you want.
    But if I don't send a signal to the BOB, Mach will think everything is fine, and the instant that AC power is restored, the machine would start moving again. Am I missing something?

    Quote Originally Posted by cebaldocchi View Post
    I have machines with two systems... my first machine I did not know how to configure mach3 and I make the E-Stop just BREAK VAC 127V line.

    Today I make:
    E-Stop just sending a sigtal to BOB / Mach3 --- using NC signal.
    and side-by-side of E-Stop button I use a ON/OFF switch to energize my drivers...

    By the way, I have never got any problem of having my PC freezing and NOT stopping when pushing E-Stop button. But IF i have, I would turn off immediately on/off switch.

    Parallel DB25 interfaces is very good and in my opinion E-Stop is enough.
    If you use USB board take care, because there is a delay and some bugs... maybe it's a good idea breaking VAC line.
    I am using the ethernet version. I bought it for exactly that reason: it is more robust than USB.



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    Community Moderator Al_The_Man's Avatar
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    Default Re: E-stop wiring, which way is correct?

    In N.A. there are 3 E-stop methods according to regulations under code, all three result in all power removed from motor devices, I use the typical control relay that has the coil of the relay at the end of the E-stop operating devices, E-stop P.B's, L.S.'s, watch dog timer/charge pump etc.
    The relay results in removing power from all contactor coils etc. a contact on the control relay can also be used to advise the controller, Mach etc that an E-stop has 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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    Default Re: E-stop wiring, which way is correct?

    I do NOT like any solution which simply breaks the mains supply, for several reasons.
    The power supply does NOT die immediately. The motors can keep running for a second or two - long enough to do serious damage to something.
    Restoring the mains power can have sudden and unexpected consequences, sometimes damaging, sometimes injurious.

    Instead my eStop button does two things.
    Obviously it sends an eStop signal to Mach3, which pretty much guarantees a smooth recovery.
    Secondly, it drops the enable line to all axis motor drivers and to the spindle driver. The axis motors freeze immediately, much faster than breaking the mains power, and the spindle stops about as fast as it can.

    I will add that if one of the motor drivers decides to flake out all by itself, that signal will have the same effect as hitting the eStop button.

    Cutting the mains was perhaps the only solution available 50 years ago. Fair enough for back then, but far greater safety is available today with other methods.

    Cheers
    Roger



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    Default Re: E-stop wiring, which way is correct?

    Quote Originally Posted by RCaffin View Post
    Cutting the mains was perhaps the only solution available 50 years ago. Fair enough for back then, but far greater safety is available today with other methods.

    Cheers
    Roger
    Regardless, the E-stop methods are still outlined in category 0,1 or 2 at least in N.A. code, there is a stipulation that power can be removed after some delay if immediate removal of power will cause damage to personnel or machine.
    Also Emergency stop will use hardware methods to remove power and shall not rely on software devices.
    If this is a DIY machine, the user can deploy any method he chooses, but for Industrial installations, the code still applies.
    For some time, Safety relays have been deployed solely for this purpose initially to a great extent in Europe, they have now caught on for some time here in N.A. There are several models that offer many different features of E-stop sequence.

    Al.

    Last edited by Al_The_Man; 09-13-2018 at 08:23 PM.
    CNC, Mechatronics Integration and Custom Machine Design

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    Albert E.


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    Default Re: E-stop wiring, which way is correct?

    Quote Originally Posted by RCaffin View Post
    Secondly, it drops the enable line to all axis motor drivers and to the spindle driver. The axis motors freeze immediately, much faster than breaking the mains power, and the spindle stops about as fast as it can.

    I will add that if one of the motor drivers decides to flake out all by itself, that signal will have the same effect as hitting the eStop button.
    Could I get you to draw up a quick diagram of how this is wired with the enable lines? Are you using a typical e-stop button with 1 NC and 1 NO contact?



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    Default Re: E-stop wiring, which way is correct?

    Also Emergency stop will use hardware methods to remove power and shall not relay on software devices.
    Because the first thing that will will will be the software! Yes, my system does use hardware.

    A quick diagram - possible, but I don't know whether it would work with YOUR drivers. I am using Gecko 320X drivers. Other drivers might need a different design.

    Cheers
    Roger



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    Default

    Quote Originally Posted by RCaffin View Post
    Also Emergency stop will use hardware methods to remove power and shall not relay on software devices.
    Because the first thing that will will will be the software! Yes, my system does use hardware.

    A quick diagram - possible, but I don't know whether it would work with YOUR drivers. I am using Gecko 320X drivers. Other drivers might need a different design.

    Cheers
    Roger

    Understood, I can figure out the details, I really just want to know if you daisy chained all the enable circuits in series, and did you connect them to the same contact on thr e-stop that informs Mach that a stop has occurred?



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    Default Re: E-stop wiring, which way is correct?

    Quote Originally Posted by secretspy View Post
    Understood, I can figure out the details, I really just want to know if you daisy chained all the enable circuits in series, and did you connect them to the same contact on thr e-stop that informs Mach that a stop has occurred?
    Typically all the E-stop devices are NAND'ed together, that is they are all N.C. in series, and at the end of the string is the enabled E-stop relay. Operation of any device drops the E-stop relay out.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


  12. #12
    ericks
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    Default Re: E-stop wiring, which way is correct?

    Option 1 is a bad design!



  13. #13
    ericks
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    Default Re: E-stop wiring, which way is correct?

    There are a few reasons i say bad design but the main one is the fact that these buttons/their contacts are usually rated at a low current rating...typically max 10A. Running your main power through one of these contacts is a bad idea. Potentially you going to overheat and burn/melt this contact



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    Default Re: E-stop wiring, which way is correct?

    Quote Originally Posted by ericks View Post
    There are a few reasons i say bad design but the main one is the fact that these buttons/their contacts are usually rated at a low current rating...typically max 10A. Running your main power through one of these contacts is a bad idea. Potentially you going to overheat and burn/melt this contact
    Hence the E_stop CR. relay!
    Which is typically 24vdc sourced.
    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: E-stop wiring, which way is correct?

    This is a rough hack from my wiring schematic.
    E-stop wiring, which way is correct?-estopcct1-jpg
    The Gecko 320X drivers have a single pin for combined Fault and Enable. I think they ran out of I/O pins. In essence I am using diodes to NAND the signals together.
    If I hit the eStop all Geckos are disabled by hardware, and so is the spindle drive. Then a logic signal goes to Mach3 to tell it we are in eStop.
    Once the fault lines have been pulled down briefly, the Geckos will hold them down, but softly.
    After I release the eStop button I can tap the Go button to pull the gecko Fault/Enable lines up and enable all the drivers.
    Ignore the big heavy black line: it is a wiring bus.

    HTH
    Cheers
    Roger



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E-stop wiring, which way is correct?

E-stop wiring, which way is correct?