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Unread November 15th, 2019, 05:17 PM   #1
ndzied1
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Simple E-Stop Circuit Question

We were having a discussion here about E-Stop circuits and more specifically using a lighted push button to power on the E-Stop Circuit.

One of the people here is saying that he's used to the light inside the button that energizes the E-Stop circuit coming on when the Estop circuit is de-energized to attract the operator's attention and so it would function as a "Reset Required" light. Circuit 2 in image below.

I haven't seen any machines like that and would say the top circuit in the attached picture looks more standard to me. Maybe some would say the light should be White instead of Blue?

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.
Attached Images
File Type: png EStops.png (96.1 KB, 241 views)
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Unread November 15th, 2019, 05:25 PM   #2
mass89
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Red when pressed, white when not pressed.
If only one option then just red when pressed, a light in a safety button shouldn't be needed to aid someone to press it.
See schneiders new harmony illuminated ring
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Unread November 15th, 2019, 05:55 PM   #3
jaden
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What I have seen commonly is the light in the red E-stop button is lit when the E-stop is pushed down. (Assumes a switch that stays down when pushed.) This is wired from a contact on the E-stop button. The idea is to see at a glance which E-stop station is preventing reset.
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Unread November 15th, 2019, 06:26 PM   #4
MHennel
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Typically I have been handling E-stops as a two stop process. The red light on the E-stop indicates that particular E-Stop push-button/pull-cord is in an active state. I then have an illuminated push-button in the control panel. The light is tied to the output of the E-Stop relay that indicates the E-Stop state. the push-button from the illuminated pilot light is tied to the E-Stop relay reset terminals. So resetting from an E-Stop is a two step process. First all active push-buttons/pull-cords need to be reset and then the E-stop relay in the control panel needs to be reset at the control with the push-button.
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Unread November 15th, 2019, 09:00 PM   #5
rupej
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How about both? One light to show control power is energized, and another to say a reset is needed? I've never seen it but as long as they're labelled well, that would be the least confusing, IMO.

Some switchgear does that, has both energized and de-energized lights to show the state. Side benefit is it shows clearly when a light is burned out!
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Unread November 16th, 2019, 07:51 AM   #6
Aabeck
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I have worked on a lot of stamping presses with attached feed lines.

With the press, feeder, steel straightener, coil cart or reel and 3 control panels there can be up to 14 E-stops on the system. If an E-stop is pressed and the press won't start finding the one E-stop to reset could take time. A look around, as long as the bulb isn't burnt out, shows which one.

They usually are latching red illuminated PB's that, along with the E-stop loop N.C. contact there is a N.O. contact that lights the operator.
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Unread November 16th, 2019, 09:51 AM   #7
roxusa
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If you are using a monitored safety relay you don't want anything else on the
e stop switch side but the loop, usually 2 loops. adding the extra contact block
will let you add a lighted switch to see which is pressed.
My machines I rewire have a dual loop safety relay on every e-stop device set for auto reset.
and my main Safety relay monitors them & has a manual reset that monitors the MCR
is off before it will reset. a bit of over kill but puts you on the switch that only has half the dual loop made or is pressed. I monitor all using the delayed aux. contacts on safety relays to PLC with a Fault page on HMI.
Customer will always approve Safer and makes trouble shooting a breeze
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Unread November 16th, 2019, 10:08 PM   #8
Rson
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E-Stop when pressed should light up (RD). This allows you to see what E-stop is pressed in.

I've seen two other things:

1. Control power reset = non-illuminated blue button.
When control power is on, it lights a 'control power on' light (GN)

2. Control power button, illuminated (GN). push to reset circuit, illuminates when control power is on.

Last edited by Rson; November 16th, 2019 at 10:19 PM.
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Unread November 16th, 2019, 10:48 PM   #9
willxfmr
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There are so many ways to skin this cat, it boggles the mind. Have seen seen most of the permutations and in each case the person implementing the idea was sure that how they did it was the only "right" way to do it. That being said, the setup I prefer is to have the light solid when the e-stop is not activated, and flashing when the e-stop is pressed. To me the advantage is that at no time, under normal conditions, should the light not be either solid or flashing. If you see one with no light, you know you have a bulb to change, or some other issue. If an e-stop has been pressed, then finding the flashing light is usually not too difficult for most operators. For the color of the light, red is what I see most, but any color would be acceptable to me.


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Unread November 16th, 2019, 11:41 PM   #10
FactoryTalktotheHand
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White is the standard for Control Power On Lights.

Also, the second circuit would be misleading. The blue light would be powered on whenever the MCR is de-energized. But there are two reasons the MCR could be de-energized. Either the E-Stop is pushed, or it's been pushed and pulled out. I would put a second N.O. contact off the E-stop to put in series with the N.C. MCR contact. That way the light only turns on if the MCR is off AND the E-stop is pulled out.
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Unread November 17th, 2019, 08:12 AM   #11
milldrone
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Quote:
Originally Posted by willxfmr View Post
there are so many ways to skin this cat, it boggles the mind. Have seen seen most of the permutations and in each case the person implementing the idea was sure that how they did it was the only "right" way to do it. That being said, the setup i prefer is to have the light solid when the e-stop is not activated, and flashing when the e-stop is pressed. To me the advantage is that at no time, under normal conditions, should the light not be either solid or flashing. If you see one with no light, you know you have a bulb to change, or some other issue. If an e-stop has been pressed, then finding the flashing light is usually not too difficult for most operators. For the color of the light, red is what i see most, but any color would be acceptable to me.


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Unread November 17th, 2019, 09:51 AM   #12
Tom Jenkins
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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.
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Unread November 17th, 2019, 10:39 AM   #13
BAJ
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Quote:
Originally Posted by willxfmr View Post
There are so many ways to skin this cat, it boggles the mind. Have seen seen most of the permutations and in each case the person implementing the idea was sure that how they did it was the only "right" way to do it. That being said, the setup I prefer is to have the light solid when the e-stop is not activated, and flashing when the e-stop is pressed. To me the advantage is that at no time, under normal conditions, should the light not be either solid or flashing. If you see one with no light, you know you have a bulb to change, or some other issue. If an e-stop has been pressed, then finding the flashing light is usually not too difficult for most operators. For the color of the light, red is what I see most, but any color would be acceptable to me.


Bubba.
+1

As a contractor I think E-Stop (and associated lights) should be implemented to follow a standard (as much as possible) on a per-site basis - stick with what they know as long as it complies with code. I think the size of the machine should also play a roll. Myself, I work on a lot of large machines, if you want to see every E-Stop operator you would be going for a long walk. 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.
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Unread November 18th, 2019, 08:46 AM   #14
doctord
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I have used the following at customer request.
A blue light in the E-Stop Circuit Reset PB. It was ON when all good.
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Unread November 18th, 2019, 09:39 AM   #15
JesperMP
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I dont think there can be a need for indicating that the E-stop is "ready" or something like that. If there is an E-stop, then it is always "ready", and it must stop everything that is in the zone that the particular E-stop covers.
Even if all machinery in the zone is stopped, or if power is off, then the E-stop is still ready, because activating it will inhibit startup when power comes back.
And I know that this covers the situation that the E-stop is pressed in a non-emergency situation, but the point is that an E-stop is always active.

We always have a contact in our E-stops to tell the PLC exactly which E-stop was activated, and this is used to generate a meaningful alarm message on the HMI. Only once have I had a customer that specifically wanted to have an lamp indication in the E-stop to quickly locate it when someone had pressed it - usually when there was no emergency. The reason was to minimize downtime, not to make the E-stop easier to locate in an emergency.
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