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Old 06-16-2013, 07:42 PM   #11
smoothlarryhughes
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Are these e-stop buttons NO or NC? Can someone explain to me the concept?

From what I am thinking is that I would use a normally open contact, and when pressed it lets current leak out the ground, therefore tripping the GFCI in the panel. Or am I completely off base here?


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Old 06-16-2013, 07:50 PM   #12
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Are these e-stop buttons NO or NC? Can someone explain to me the concept?

From what I am thinking is that I would use a normally open contact, and when pressed it lets current leak out the ground, therefore tripping the GFCI in the panel. Or am I completely off base here?
You have it exactly correct.!


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Old 06-16-2013, 08:28 PM   #13
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So the implication here is that for the e-stop, "normal" means "button up" and "not-normal" means "button down," yes? That would be consistent with a push-button, but a bit counterintuitive to me, as "activated" state implies to me "not normal." Incidentally, Automation Direct sells this illuminated e-stop http://www.automationdirect.com/adc/...d/GCX3226-120L that only includes a NC contact block, which only confuses me further.

Do I have it right in the first sentence? Am I missing something here? Thanks.
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Old 06-16-2013, 09:20 PM   #14
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So the implication here is that for the e-stop, "normal" means "button up" and "not-normal" means "button down," yes? That would be consistent with a push-button, but a bit counterintuitive to me, as "activated" state implies to me "not normal." Incidentally, Automation Direct sells this illuminated e-stop http://www.automationdirect.com/adc/...d/GCX3226-120L that only includes a NC contact block, which only confuses me further.

Do I have it right in the first sentence? Am I missing something here? Thanks.
???

What?

A N/O switch has a open contact when NOT activated.!

Illuminated? What to Hell for????

Confused... You betcha...
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Old 06-16-2013, 11:27 PM   #15
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So a NO pushbutton switch is open when the button is up, and closed when the button is down (activated).

A NO e-stop is open when the button is down, and closed when the button is up (activated)? So "normal" in the case of the e-stop is "button down," while "normal" in the case of the pushbutton is "button up?"

Yes, I was quite confused, but the illumination is a red herring.
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Old 06-16-2013, 11:58 PM   #16
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So a NO pushbutton switch is open when the button is up, and closed when the button is down (activated).

A NO e-stop is open when the button is down, and closed when the button is up (activated)? So "normal" in the case of the e-stop is "button down," while "normal" in the case of the pushbutton is "button up?"

Yes, I was quite confused, but the illumination is a red herring.
Sorry. Your logic is twisted..

N/O = contact is open when the switch is at rest.

N/C = contact is closed when the switch is at rest (not - activated). (I just edited my error - thanks Kevin)

An illuminated switch for this application significantly complicates the application. Don't go there...
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Old 06-17-2013, 12:15 PM   #17
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So a NO pushbutton switch is open when the button is up, and closed when the button is down (activated).
Correct.

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Originally Posted by jeffmeh View Post
A NO e-stop is open when the button is down, and closed when the button is up (activated)? So "normal" in the case of the e-stop is "button down," while "normal" in the case of the pushbutton is "button up?"
False. The NO e-stop is open when the button is up (normal condition for the switch), and closed when you mash the button down (activated). Unless you have some weird push-button switch that when you push it, it goes up. The switch you showed (the illuminated one) has a NC block, so it wouldn't work for the GFCI trip method. You could use that button for the power-flow through to the contactor method - normal condition, power flows through to the contactor coil. Mash the button, the NC block opens, power no longer flows to contactor coil, panel turns off.

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Yes, I was quite confused, but the illumination is a red herring.
As the switch listed only have a NC block, you'd basically have the switch illuminated when normal (not activated), and turned off when activated (pushed down) - you'd have to install a NO block if you wanted to have the light turn on when activated, but if you went with the GFCI flip method, there'd be no power to illuminate the light anyways.

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N/O = contact is open when the switch is at rest.

N/C = contact is closed when the switch is activated.
I think the N/C logic is backwards. N/O is open when switch is at rest (closed when switch is activated). N/C is closed when at rest (open when activated). The description above would be the same switch, which is a N/O contact block.

-Kevin
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Old 06-17-2013, 03:00 PM   #18
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Thanks Kevin. So according to your definition above, "normal" position for an e-stop is button up. If I use the NC e-stop switch listed to switch a NO, DPST contactor, it would illuminate and close the contactor when the button is up, correct?
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Old 06-18-2013, 10:30 AM   #19
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Thanks Kevin. So according to your definition above, "normal" position for an e-stop is button up. If I use the NC e-stop switch listed to switch a NO, DPST contactor, it would illuminate and close the contactor when the button is up, correct?
Bingo. Power would flow from your supply via any sort of keyed switch you may or may not use, through the CLOSED switch block (as Normal for an e-stop is 'up' IE not depressed) to your contactor coils. This would in-turn cause your coils to energize, causing the contactor to switch from it's normal at-rest condition of being open, to being a closed and fully functional contactor, thereby allowing the rest of your panel to be powered by your primary supply. In this condition, the e-stop button could also be illuminated.

In this configuration, the EMERGENCY STOP button is not actually being used for any sort of emergency stopping on a regular basis, but is instead simply acting as a large mushroom switch to provide power to your contactor coils. While it goes against the basic fundamentals of using a piece of emergency equipment for routine function, that's more of a SOP issue than an actual functionality issue.

As described above, your panel should function fine.
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Old 06-18-2013, 01:24 PM   #20
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Thanks again Kevin. My confusion was around which state was considered "normal" for an e-stop. Once knowing that normal is up, all else logically follows.

P.S. One could also consider normal the state of lowest physical energy, i.e., the state the device would fail into, which would be down in the case of a twist-up e-stop. Hence my confusion.



Reason: P.S.
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