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Green and Red indicator Lamps

  1. Dec 3, 2015 #1
    Hey all, I am curious what does it mean when the Red or Green indicator lamp is on. I know generally red means dangerous situation while green means safe zones but what about the running of say machinery?
    Let me put in 2 scenarios and do share your thoughts with me which colour is for which and why? :)

    1) Machine is running
    2) Motor has stopped
  2. jcsd
  3. Dec 3, 2015 #2


    Staff: Mentor

    In the USA, Green means on and red means off, at least most of the time. But there are so many exceptions, that it is really bad to depend on colors alone.



    Below is an example of the exceptions.

  4. Dec 3, 2015 #3


    Staff: Mentor

    Conventions vary across industries:


    You will have to see where the machine will be used and use the prevailing convention.
  5. Dec 3, 2015 #4
    Ahhh I see... It's interesting to know that it varies! Ive always thought that it would be standardised across the world much like the colour scheme of the traffic lights. Thank you all for sharing and yeap I will enter the link provided by jedishrfu and understand more! :)
  6. Dec 3, 2015 #5


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    Context is everything. For years red LEDs were/are used to indicate equipment is powered up. Mostly became red LEDs were the cheapest colour.
  7. Dec 5, 2015 #6

    jim hardy

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    I worked in US utility industry from 1969-2004.
    At my utility RED meant a device is ACTIVE and could hurt you.
    a valve is capable of passing fluid ie OPEN
    a switch or circuit breaker is capable of passing current ie CLOSED
    a pump or motor is TURNING so don't grab it

    for us, a valve that's only partially open has BOTH lights ON indicating it's at least mildly active .
    Some utilities in early days used both lights extinguished for partially open, but we preferred that both lights out tell you it's lost power and you need to fix something.

    I believe that has become a utility industry standard .
    ANSI? ISA? NFPA? ISO? There are sooo many standards organizations nowadays.

    Observe the red "Hot Surface" light on modern cooktops.

    old jim
  8. Dec 5, 2015 #7


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    It's tricky to depend solely on colors for this type of safety situation, since there is a fraction of the population which is red-green color blind.

  9. Dec 10, 2015 #8


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  10. Jan 17, 2016 #9
    Here in the UK we follow the EU Low Voltage Directive and under our own Machinery code BS60204

    Red indicator - Emergency (Hazardous Condition)
    Green indicator - Normal condition

    Like others have said there are many exceptions and the regulations do state 'unless otherwise agreed' so there is no real hard fast rule but on recommendation, I often go outside the recommendations due to other machinery close buy using differing codes so as to lessen the confusion to the operators.

    Noting here you have specified Indicator Lamps and not the colour of illuminated push buttons or switches which also have there own recommendations.
    Last edited: Jan 17, 2016
  11. Jan 17, 2016 #10


    Staff: Mentor

    Of course we have neglected the red/green convention that really is used world wide with no exceptions that I know of. That is the left/right lights used on boats and aircraft, and the red/green lights on red/green navigation buoys.
  12. Jan 17, 2016 #11


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    The ONLY colour, for many years. Can you really be that young. You sound /read soooo mature. :wink:
  13. Jan 17, 2016 #12


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    Did you know that the buoyage in tidal channels is different on the two sides of the Atlantic? That is more scary than a simple 2:1 voltage difference imo.
  14. Jan 17, 2016 #13


    Staff: Mentor

    No I didn't know that Sophie. Thank you. I'm reading up on that now in Wikipedia. It says that there used to be 30 different systems, but now there are just two. At least none use blue/yellow buoys.

    The convention about which is left or right is not as critical as it could be because you can't always tell if your course is toward or away from the port. I recently boated from coast to coast in Florida. In that passage the left/right buoyage necessarily flips at an arbitrary point somewhere in the middle. So no matter what the convention, boaters must be alert for those places where red/green left/right flips.
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