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Author Topic: E-Stop: Latching or Momentary?  (Read 2243 times)

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E-Stop: Latching or Momentary?
« on: May 01, 2015, 04:06:19 PM »
Hello all:

Absolutely new at this; am converting a G0484 Mill/Drill to CNC. Question that is bugging me now is: Does the E-Stop Switch have to be a Twist to Release, ie. Latching, or can it be a Momentary Pushbutton? Concern is that if Momentary does Mach3 reset the emergency stop function and go back to doing whatever it was doing before the OMG moment. Hope to hear from someone. Have searched for the answer but have not been able to find anything on this topic. Take care.

Burt
Re: E-Stop: Latching or Momentary?
« Reply #1 on: May 01, 2015, 06:22:38 PM »
I have both a momentary and a latching.
The momentary which is mounted on my switch panel, is connected via software (Pokeys) to Mach3. Mainly used to reset Estop situations when something triggers an Estop. When used in a panic situation, it does not activate till you release the pushbutton. Pressing and holding does not activate, its only when you take your finger off the button.
The twist and release shuts off power to the drivers and VFD.
When coming out of an Estop, Mach will wait for a command to continue - Cycle Start, Jog etc
Re: E-Stop: Latching or Momentary?
« Reply #2 on: May 01, 2015, 06:31:34 PM »
Thank you for the response. Being a dinosaur I do not know what Pokeys are. Thought was to wire both the Momentary and Latching in series, using the NC contacts. Now I have to do more research. I like the idea of activation of the momentary on release rather than having to hold it down. Take care. Burt

Offline mc

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Re: E-Stop: Latching or Momentary?
« Reply #3 on: May 01, 2015, 06:51:25 PM »
Depending on where you are in the world, from a safety regulation point, all e-stops should be of a non-self resetting type i.e. a twist to reset type.

I know in Europe there is also a requirement for all user buttons to work on low voltage (defined as 48V or less), and a reset must be required after any e-stop i.e. the system can't start working again just by resetting the e-stop button.

Now the regs are over, for the size of machine you're using, I'd apply some common sense, as it will be capable of doing plenty damage if things go wrong.
Personally, I'd recommend you use latching E-stop buttons, that control the power supply(s), with Mach being notified of an E-stop having occurred. I would never recommend that you rely on any computer to handle the E-stop, as if the computer happens to be the cause the of the problem, then you run the risk of the E-stop being ignored. By killing the power supplies, even if the computer is doing something it shouldn't, the machine will stop, and remain stopped until you reset the E-stop button.
Re: E-Stop: Latching or Momentary?
« Reply #4 on: May 01, 2015, 07:21:27 PM »
mc:
Just a retired hobby guy in Virginia. However, I understand your points. Presume that I would need to connect one or more relays to disconnect the 36VDC Power Supplies (X2) 115VAC inputs.  Reckon wiring the latching E-Stop switch N/C contacts in series with the relay coil. would do the job. No reliance on the PC that way. Have two latching style switches on order from China so I guess I will use the Momentary switches for something else. Thanks for the information. Take care.

madeintheshed:
Found some information about PoKeys, outside my price range right now but does look like a good way to gain inputs, etc. Thanks for the information as well. Take care.

Burt