E-Stop light: On when On or On when Off

[tlarmstr 0]

Here is a question for all of you that have been programming for many moons. Is it proper to have the E-Stop light light up when the machine is running and safe, or should the E-stop light be on when the E-Stop button is pushed. I have seen it both ways and a programmer where I work has it on when the machine is running and safe. just want to hear some opinions on this. thanks

[Beryl 0]

I too have seen it both ways. I have never seen or heard of a "standard". IMO the light should be on when the button has been pushed but, there are valid arguments both ways.

[Guest Guest]

I had also seen both versions, however I inclined to go with the Estop only lighting up when the E-stop button is engaged. Just as when a start button is illuminated to indicat the button has benn pressed and a positve action has occured, such as the motor is running for example. With the E-stop engaged i prefer to have it light. It all depends on your situation and customer preference, I guess! In my opinon I think initially I would be startled for a second and thought something out of the ordinary If the start button was iluminated green and the e-stop was illuminated red. But in defense of someone wanting all illumiation I guess this would be a good test for burned out lights!!!

[Guest Guest]

IMHO lighted indications should be minimized. The estop lamp should probably light only for an estop condition and so draw attention to itself. Otherwise you are expecting the operator to notice "the dog that isn't barking".

[jfwoodland 0]

I think the most important thing is that all machines in an area operate in the same manner. Operators will be confused if machine "A" does one thing and machine "B" does another. At one company I worked for, we used the following convention: Emergency circuit not tripped and no E-stops depressed = all e-stop lights off Emergency circuit tripped but no E-stops depressed (door switch, etc.) = all E-stop lights on steady Emergency circuit tripped and E-stop(s) depressed = flash depressed E-stop light(s), all the rest of the E-stop lights on steady It seemed to work great for us.

[JimRowell 1]

My personal standard is to use lights to indicate active conditions only. I never use a red light to indicate "running" or "power on" such as was traditionally done. Nor do I use lighted indicators that are lit when NOT active. The later was commonly seen in the old days. The thinking was that it helped locate a button quickly for a user in an emergency. If I have buttons that will be in a dark area and may not be obvious, then I provide general illumination for the panel. A big red palm-style e-stop doesn't need to be lit to be found quickly. Anyway, my synopsis is to only use lights to indicate an "active" condition meaning one of the following: Green light: ON, RUNNING, OK, SAFE, READY and similar positive, normal and "nice" things (green = "go"). Amber: CAUTION and similar warning type of things. Red light: EMERGENCY, DANGER, OVERLOAD, ERROR and similar negative or "nasty" things (red = "stop"). You can lessen the safety hazard/confusion caused by burnt-out lamps by using green for on and red for off but I tend to not use any indicator at all for off since too many lamps is sometimes just as big a problem and it also detracts from the impact of the colour red if people see it all the time. I like to save red for high impact messages. I also don't use incandescent lamps anymore - led's are just so much more reliable. It can be confusing to use green to indicate both "running" and "safe" (and dangerous) so I'll generally use an unusual colour for "safe". For instance, on punch presses, I use green for "running", red for "fault", blue for "safe". Safe is defined in this case as the main motor may be running but the cycle controls are locked out, ready for machine loading (with appropriate cautions on the part of the operator). Activating an e-stop kills all power and all lights go off. No illumination is allowed with the e-stop pressed because we don't want any power available that might be find a short path to the clutch solenoids, etc and create a hazard (possibly the very reason the e-stop was pressed in the first place). In other words, an e-stop is a complete power-down in this case. Jim Rowell

[tlarmstr 0]

thanks for the input, no pun intended. My thought is the same as all of yours, to bring attention to the one item that has stoped the machine. I know that some people like to have the light on when it is running just so the operator can see the E-stop in an emergency, but I think that if the operator doesn't know where the E-stop is they shouldn't be operating the machine. thanks again

[darrenj 0]

Have you seen and talked to half the people who operate those machines!!! I know thats not fair but sometimes i wonder....i work on many machines where there are multiple Estops...I always program so the light comes on if its pushed..all others flash..You would be suprised how many times i have been called in at 3.00am just to pull an e stop button out... I must share the best one with you...I was called in at 1.00am sunday night...A machine wasnt working...i walked in and talked to the operator he said everything was fine for the first few hours then stopped....I looked around and the estop was pressed..so i pulled it out and hit reset...eveything came back up...i then asked him if he pushed the button..He said "yea...it was noisy with all those fans running so i pushed that and they stopped...." He couldnt figure out that after he pushed the button nothing worked......As said some times i wonder???!!!

[JimRowell 1]

I know what you mean but on the other hand, I've heard a lot of stories about the "unscheduled break schedule" too. Actually I've seen a few of them myself. You know, the fuse that magically vibrates out of place (the one that takes 2 hands to push back in), the wire that just pops off, etc. One of my first service calls to a certain printer was to remove paper from behind a fuse. Are you sure there wasn't the odd titter going on? A not so straight face? Some of the dumbest characters I've known could make a machine do things that I could only dream of despite the fact that I designed the controls. Maybe not so dumb after all.

[RichWargo 0]

I agree with Jim. E-stops should kill ALL the power, including control power, hence no lights. Safety issue. Would rather physically check all e-stops for a machine, than have stray voltages running around. I seem to recall someone made an E-stop that had a mechanical color change, i.e., a different color would be mechanically pressed against the button when the button was operated. That would be preferable to an electric light, LED or otherwise.

[Pierre 1]

Having done a few control system in the area of "medical air" supply for work inside vessels O allways tend to have 2 lights for the "emergency" situations. For a good or OK call, Green and-not Red For a failed system, Red and-not Green This way it cannot be missed even if all light are burned. The signal comes from a single 1P2P relay. It could be overkill but what's the cost of one pilot light?

[KinK 0]

I have put a battery operated E - Stop in some places that I felt required the E-Stop illumination(having been called in at 1am 3 consecutive nights in a row) so I put a 6 volt battery in the cabinet and hooked up a flashlight bulb inside a AB housing so that when the E-Stop was pushed this light would come on but all the power would still be off in the panels.

[darrenj 0]

some good points made here..However if a Estop is pressed i prefer that the controller still maintains power. That way you can start where you left off. The estop is wired in series with the power for the output cards so there is no chance of anything moving on you...(Ecept in hydraulics..for that i add a second contact on my estop to energize a bypass solinoid to release the pressure) But again all i have said above is law in canada...No emergency stop can rely on logic to stop the machine..it has to be done electricaly..

[Camel 1]

The e-stops we use light up when pushed. It comes in handy when someone pushes them when they aren't supposed to, you can walk right up to the one with the light and pull it back out. Remember the K.I.S.S. method!!! Edited 16 Sep 2004 by Camel

[brucechase 1]

I've enjoyed reading these posts, it has made me think of many things that I haven't considered before. On power switchgear, Red is ON or POWERED and Green is OFF which is often different from control system and motor controls. I never did like that much. I have had a lot of opportunity to handle this e-stop at this company. For the most part, I have very few e-stop switches. Each machine usually has one or two at the main control panel. These are always the non-lighted big mushroom type. Instead, each machine I have uses rope (cable operated) switches. On a small machine in which I have only 1 or 2, I usually just use a non-lihgted switch. In addition, I have thousands of feet of conveyor that goes every which way. These conveyors are protected by multiple rope switches along the entire length. Since there are only a couple of control panels, there are as many as 15-20 e-stops on 1 panel. On these, I have added a light on each e-stop that lights when the switch is activated. This allows us to go right to the tripped switch and reset it. In the beginning, there was no light so checking each e-stop would take 5-10 minutes (if we got them all). That amount of downtime is way excessive for a reset (you had to go to the e-stop to reset the switch and then go back to the panel to restart the system). Even though this was an improvement, it wasn't the easiest. I have lately added a contact from the e-stop relay right to an input of the plc. From there, whenever the e-stop is activated, I pull up a bitmap drawing of the system on a Panelview and light a box to show everyone where to go. This seems to work very well. I know this was a little off topic but to summarize, I guess I like the e-stop light to be on when the e-stop has been activated. Don't know if this is right, but it seems to work well here Bruce Chase Edited 16 Sep 2004 by brucechase