Here we go again: Stack light colors

[Lancie1]

For Condition of Process:
Red - Emergency, Yellow/Amber - Abnormal, Green - Normal

For State of Equipment:
Red - Faulty, Yellow/Amber - Abnormal, Green - Normal

Long ago in a time far away, the NEMA and JIC standards were exactly the opposite. If you had a light on a motor starter, it had to be RED when the contactor was energized, red meaning the equipment is running normally and is dangerous. It think it was around 1980 when the standards started changing. If you see some old 35-year-old equipment here in the US, it may have opposite colors to what you think now.

 

[Johnster]

if I see a green-iconed screen at my 1980's vintage power plant- It means that nothing is running. Pumps, motors, valves and electrical busses(!) are red when running or energized.

At this point, to reverse this convention would cause so much confusion as to be dangerous.



More on stacklights - I always dreamed of blink codes on stacklights - like a fast blink means jammed, a slow blink means low product, a double fast blink means communication error <- stuff like that.
Thats not very easy to program in ladder, but flashes and combinations can be used to Annunciate more conditions than just 1 per light.
Operators need to know this though.

-John

 

[Lancie1]

I always dreamed of blink codes on stacklights - like a fast blink means jammed, a slow blink means low product, a double fast blink means communication error <- stuff like that.
Thats not very easy to program in ladder,...

Au Contraire, my good friend. I have been programming alarm blink codes for years, in RSLogix, Automation Direct Logic, and Siemens. The first one was difficult, but now it is just copy and paste. I have posted examples here before, and also in the Downloads section. I would be glad to post another if you are interested. My version uses a 2-digit code, a series of blinks with short pauses between, followed by a longer pause, then the second digit, followed by longest pause, then repeats. If a maintenance really wants to know what the alarm means, he counts the blinks on the way to the machine, then looks at the key code taped to the machine to know what caused the alarm. See "Alarm Codes" (RSLogix) posted in Allen-Bradley section.

http://www.plcs.net/downloads/index...ey&PHPSESSID=d4d88aa3324d2c84650d37b8ed3838ef

 

[TConnolly]

So it sounds like Alaric is thinking in terms of personnel safety, but the corporate borg is thinking in terms of "Condition of Process" or "State of Equipment."

The corporate borg is thinking that Amber should indicate equipment is running, green means load the next part, red means not running.

NFPA gives the option of having red indicate either a caution or unsafe condition if its indication purpose is safety, or a critical fault if the indication purpose is equipment status. Green can indicate "Safe" or "Normal" depending on purpose of indicator. However in no case is amber indicated for "running" which is what was originally suggested.

So with a red, amber, green stack light, and adhering as close as I can to NFPA 79 10.3, I can have two fault indicators, red for severe fault, amber for minor fault, and one "normal" green indicator, but in this process I don't see the need for two different kinds of fault lights, or I can use red to indicate "danger" and green to indicate "safe" but both red and green indicate that the process is normal, just different parts of the process.


Isn't it amazing how the simplest things can turn into a #10 can full of worms.

 

[Jim Dungar]

Isn't it amazing how the simplest things can turn into a #10 can full of worms.

Back in the 80's, Square D motor control devices were shipped as standard with Red = On lights, while Allen-Bradley shipped theirs as Green = On. You know how costly it is to buy non-standard equipment.

 

[xzen]

For the sake of color-blinded and for the sake of "information forestry" I don't like the green light very much. When in normal run a machine should say as little as possible and preferably nothing at all to humans!

 

[TConnolly]

When in normal run a machine should say as little as possible and preferably nothing at all to humans!

I like that.


But there are engineers working somewhere in Japan right now trying to make a computer conversant.

Humans OTOH should be able to saw whatever they want to the machine and call it what-ever vulgar name they want.

 

[Clay B.]

Humans OTOH should be able to saw whatever they want to the machine and call it what-ever vulgar name they want.

Been cussing machines since I started working on them. That is what I like about machines. You never hurt their feelings when you call them a peice of junk.

Never had to go to "sensitivity" training because I called a machine a PC incorrect name...

 

[seaston_65]

Let's not forget about the Buzzers you can add to the stack. Here we've got a line of 6 identical machines, all automated. 1 operator per 2 machines loading and unloading boxes.

Whenever there is a fault, the red light goes off, but of course that can be igrnord, so we've added a buzzer that won't stop till the fault is cleared. Each pair of machines has a unique buzzer sound, so if you're working on machines 1&2, you listen for your own buzzer sound.

Amber is the machine is either stuffed or starved

Green is running.

 

[Lancie1]

Never had to go to "sensitivity" training because I called a machine a PC incorrect name...

Clay, me either, but once I was working with this young woman. She got married one week, and the next week she came in wearing this new loose dress. So I pretended like I thought it was a maternity dress and said, "My, you sure are a fast worker!" I was called on the carpet and almost fired because of that comment. Turns out the girl was already pregnant. How was I to know? For months after that I had to attend meetings, get retrained, and get my attitude re-adjusted. They didn't succeed, because my attitude was "I'm getting out of this snakehole as soon as possible" and I did.