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Unread November 18th, 2019, 09:50 AM   #16
Christoff84
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The way we do ours is to have a lighted blue PB for the safety reset.
Off = Safeties Broken OR Light burnt out
Blinking = Safeties ready for reset
Solid = Machine Enabled / Safeties Reset

We also do the lighted e-stop just for ease of seeing which button was pressed to shut the system off.

Mostly we use programmable safety controllers (Omron G9SP in most cases) so the blinking PB is pretty easy to accomplish.
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Unread November 18th, 2019, 10:11 AM   #17
jimtech67
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We do the following:


Lighted maintained E-Stop PBs (Red)
Lighted momentary E-Stop Reset PB (white)


E-Stop PB is lighted when pressed (E-stop active)
Reset light is off


E-Stop PB closed (E-stop NOT active)
Reset PB is pressed resetting the circuit.
Reset PB light is on when the e-stop circuit is reset
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Unread November 18th, 2019, 10:28 AM   #18
mbartoli
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Quote:
Originally Posted by BAJ View Post
+1

We have always pulled the status of all E-Stop operators into the PLC and made an HMI status screen to help locate the tripped device(s). The growing use of safety PLCs has made this really easy. As for the hardware, my personal preference is non-illuminated E-Stop mushroom heads and a separate "E-Stop Reset/OK" white illuminated PB with an HMI status screen and alarm banner/history.
This is the way we did it when I worked for a large integration contractor that built automation systems for the OEM automotive industry. Adding a NC contact to each e-stop button wired back to the PLC and providing an e-stop status screen gives immediate indication as to which one is pressed.
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Unread November 18th, 2019, 12:03 PM   #19
FactoryTalktotheHand
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Quote:
Originally Posted by Tom Jenkins View Post
And how does an operator looking at the light on the E-Stop know if it means "I'm pressed" or "Power is On"?

I avoided the confusion by having a separate pilot light labeled "Power On" and an indicator, either a pilot light or an HMI alarm indication, labeled "E-Stop Pressed". You shouldn't make an operator try to read your mind.
I've seen people use the red lights in the E-Stop to indicate that Control Power was on. I feel like this is misleading in most cases. In my mind, red lights mean something bad is happening/has happened. If I see an E-Stop lit red I think it's telling me it's been pressed. If the light just turns off when it's pressed, then it can kind of lose itself in the background and be less noticeable.

This might be the opposite for power plants though, where red means something is on (and thus a hazard). It really just depends on the site and what those operators are used to.
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Unread November 18th, 2019, 04:34 PM   #20
Tom Jenkins
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Quote:
Originally Posted by FactoryTalktotheHand View Post
It really just depends on the site and what those operators are used to.
I agree - the lack of a consistent color code for pilot lights is a PITA. I use to carry a bag of spare lenses to start-ups so I could swap out if needed to meet operator preference.
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Unread November 19th, 2019, 11:29 AM   #21
Geospark
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Quote:
Originally Posted by ndzied
...Note that this is a simplified circuit. We almost always use dual channel e-stop circuits and safety relays now but the idea is to talk about if you would use a lighted pushbutton to reset the safety circuit and if so, how would it function.
Hi Norm,

I'm going to take your advice here and, for the most part, ignore the traditional wiring diagrams you provided, as they are not Safety circuits, at all, and in my opinion we really should not be referencing them when going to discuss resetting a Safety circuit.

Anyway, that's just my two cents on that...

There are indeed IEC (International Electrotechnical Commission) Standards out there for these colour codes, for both push button actuators and indicators, resets and whatnot. These International Standards are usually disseminated to the various Regional and National Standards. It just seems like most folk don't know of them or are not too inclined to follow them?

A bit of light reading here from a previous thread in which I "get into" the colour coding on an illuminated Emergency Stop reset push button, among other things...

E-Stop manual reset button

However, I will say, as I did somewhere in the other thread, that these Standards are not solely applicable to Safety circuits. In fact, they are not called out as Safety related at all. We can actually apply these Standards to the example non-Safety MCR circuit here, or any other standard control circuits, if we wish. They just advise us as to what is acceptable in general and we must interpret these Standards ourselves when applying them to circuits that happen to be Safety related.

Example: non-illuminated reset push button

Colour: BLUE
Meaning: Mandatory action
Description: Actuate in a situation which requires a mandatory action
Examples of application: Resetting function

A reset of a Safety circuit is a "Mandatory action". As such, the IEC Standards dictate that BLUE is the preferable colour to use here. Not because it is for a Safety reset, but because it is for a "Mandatory action". A standard reset function may also be classed as a "Mandatory Action". Therefore, we cannot say that BLUE is reserved for Safety resets. Any Mandatory action may use the colour BLUE.

Illuminated reset push button

Colour: BLUE
Meaning: Mandatory action
Description: Indication of a condition requiring operator intervention
Operator action: Mandatory action

Again, BLUE is the preferred colour to use for the indication of a Mandatory action. Note how the wording suggests that the ON state of the BLUE indicator is required to signify the Mandatory action (reset) is required, and not the OFF state.

Typically, for Safety resets, an illuminated BLUE reset push button will normally be turned OFF when the Emergency Stop Safety function is reset. When the Safety function is tripped, the BLUE indicator will turn ON to signify that the Mandatory action reset is required. Another method used is to make the indicator flash to signify the reset is required. The method I "broke down" at the end of the linked thread is also OK, by my interpretation of the Standards. That is, normally OFF when healthy, flashing when tripped and E-Stop still latched, solid ON when E-Stop unlatched but still not reset, and OFF again when reset. I have also gone through the flashing indicator frequencies set out in the Standards.

I'll let you read the linked thread, if you wish, and if any questions, fire away.

Regards,
George
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Last edited by Geospark; November 19th, 2019 at 11:31 AM.
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Unread November 19th, 2019, 10:04 PM   #22
rpoet
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I run dual-circuit E-stop loops from the buttons back to the safety relay. Each E-stop button has a self monitoring contact block, as well as an additional NC block (beyond the two needed for the loops). That additional block reports back to the PLC, and the PLC controls a red LED indicator next to the E-stop button.

That indicator light shows the status of the individual button as well as the whole system:

Solid red: System OK - no E-stops pressed, system reset.

Strobing red (0.1sec ON, 0.1sec OFF): that particular E-stop has been actuated. Other non-actuated E-stops blink slowly (0.5sec ON, 0.5sec OFF) to tell other operators that the system has been E-stopped.

Slow blink (0.2sec ON, 0.8sec OFF): all E-stops released, system not yet reset.

The E-stop reset functionality is typically part of the operator station, on the touchscreen. Pressing the RESET button resets the safety relay through a PLC-controlled interposing relay. I've not needed to do it yet, but I could also place a RESET pushbutton at each E-stop, if necessary.

I've pretty much given up on lighted E-stop buttons. As much as I like the idea of a single-device solution, they're just too fragile. A non-lit E-stop mushroom (twist to release) and a separate 22mm LED indicator are the way to go to operator-proof things for me.


-rpoet

Last edited by rpoet; November 19th, 2019 at 10:06 PM.
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Unread November 20th, 2019, 06:13 PM   #23
dogleg43
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So much for a “simple E-Stop” question. 4 days and 22 answers/posts.
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