Emergency Stop return signal

pedro_nf · Nov 22, 2018

Hi all,
The Emergency Stop button is connected to the security relay etc and cuts the machine power. My question is not about the safety circuit side of the Emergency Stop but rather the information of its state (pressed or released), so I can display it in the screen. Should I use a Normally Closed (NC) contact or a Normally Open (NO) contact? Is there any rules or norms about that?
Thanks in advance,
Pedro

JesperMP · Nov 22, 2018

No, you are free to choose N.O. or N.C. for a contact signalling the state to the operator (via a lamp, or via the PLC and HMI).

g.mccormick · Nov 22, 2018

You can also get lighted estop buttons. I like to use lighted buttons with no status contacts.

Aabeck · Nov 22, 2018

+1 on g_mccormick's idea.

I used to work in a stamping plant where the automatic presses with feedlines could have up to 11 E-Stops on the line. If one was pressed it lit up, so no one had to walk around checking each one - it was the one that was lit.

g.mccormick · Nov 22, 2018

g.mccormick said:
You can also get lighted estop buttons. I like to use lighted buttons with no status contacts.

That should have been lighted and with N.O. status contacts

pedro_nf · Nov 22, 2018

Thank you all for these infos!

Aabeck · Nov 22, 2018

g.mccormick said:
That should have been lighted and with N.O. status contacts

That's how I read it. Guess I didn't notice the case and lack of periods when speed-reading it.

GaryS · Nov 22, 2018

I like to use lighted E Stops where possible.
and use N.C. contact back to the PLC inputs. That way I can use the input in the program as a stop command / run permissive and on the HMI to show what E-Stop is activated.
If I don't has all E-Stop inputs on you can't run. Also use it to do any housekeeping I need.

dogleg43 · Nov 23, 2018

Lighted PB, maintained operation, wired in a fail safe mode

Rson · Nov 23, 2018

Lighted E-stop button with 2 N.C. contacts for the safety.

1 N.O. contact for the light (on when pressed) and use the same N.O. contact into the PLC if you have one

Emergency Stop return signal

pedro_nf

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g.mccormick

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Aabeck

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