LED yellow and green wavelengths

Discussion in 'General Electronics Chat' started by lotusmoon, Nov 3, 2013.

  1. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    Hello everyone, I have been happily making my variable frequency LED flashers.
    Thank you for all of your help and interesting conversations.
    I have been using different colours and have a question about yellow and green.
    On the internet green is 520 to 565 nm and yellow is 565 to 590nm. But what I am finding with through hole LED'S is that green is not finishing until around 575 and the yellow starting at 583 and finishing at 588. which makes the spectrum of yellow very small. I could not get any answers for this from where I was purchasing them. Does any have any ideas why this is happening with yellow LED's?
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Let's start with why this is important? Why do you need a specific wave length?

    Do they need to color match?
     
  3. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    I would like a larger selections of yellow like a mid range yellow which would normally be around 570nm which with both farnell and rs components is green. At this wavelength the leds are diffused green where the glass is green.
    Also I am just interested why this is so, the suppliers have no explanation for it.
    I thought that may be mid yellow as light might be almost just clear light? so as not yellow or green
     
  4. JohnInTX

    Moderator

    Jun 26, 2012
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    Mouser has a great parameter selectable list here. If you don't want to go with them, at least you can get manufacturers, part numbers and specs.

    Wavelength is wavelength but there can be some variance in what a particular color is called vs what you think it should be called. That said, the default reference on all matters scientific (Wikipedia) calls 570nm green, as do the manufacturers.

    Have fun!
     
    Last edited: Nov 3, 2013
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  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Perhaps consider using an amber LED? One person's amber might be another person's yellow.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I googled for a colour spectrum and found this;

    [​IMG]

    which may be of help. Personally I don't like a greeny yellow LED, a good "yellow" LED to me is pure yellow or slightly on the orangey-yellow side.
     
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  7. John P

    AAC Fanatic!

    Oct 14, 2008
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    I am mystified by the statement "On the internet green is 520 to 565 nm".

    Most of us are using RGB displays, where we see a mixture of the output of color phosphors, or the equivalent on LCD screens. That makes sense when you consider that our eyes have matching red, green and blue sensors (cone cells) though they aren't very highly filtered for color, so other hues are "seen" by overlap of the cells' response. Computer displays match what our eyes can see.

    This explains it all:
    http://en.wikipedia.org/wiki/Color_vision

    You can get LEDs in a wide range of hues. I just saw a discussion among model railroaders about green LEDs used as railroad signals, and how the most common type isn't the right color--"signal green" is actually a blue-green shade at around 510nm. It's possible to get LEDs that color, but they cost more. That parametric list on Mouser is a good place to see the variety.
     
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  8. bance

    Member

    Aug 11, 2012
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    Have you thought about using RGB leds to mix the exact colour you want?

    HTH Steve.
     
  9. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    Thank you for this. I have been doing this but i was under the impression that red, blue and yellow were the prime colours to mix with.
    I had notice someone had also mentioned that the cones in the eyes recognise red blue and green and mix them. Do you have more information on this?
     
  10. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    I have been looking at this. I can not see how to make green with with yellow and blue. But I can not see what combination of green red and blue would make yellow?
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I think you are confusing subtractive and additive colour mixing. LEDs work additively, so
    Gn+ Rd = Ye
    Gn + Bu = Cyan
    Rd + Bu = Magenta
    Gn+ Rd + Bu = White
     
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  12. John P

    AAC Fanatic!

    Oct 14, 2008
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    Strange as it may seem, a combination of red and green lights will produce a perceived color of yellow. Look at yellow on a computer monitor with a good magnifier and you can see the red and green dots. Red + blue = magenta and blue + green = cyan are much more intuitive.

    Don't think about mixing paint, think about the inks used in color printers, where red green and blue can be re-created with cyan, magenta and yellow.
     
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  13. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    Thank you for this information it is very interesting and I will experiment with it. It is great that I can produce yellow with red and green.
    as a question do these mixes of coloured light produce a perceived colour or will the wavelengths somehow combine to form a new wavelength?
     
  14. MrChips

    Moderator

    Oct 2, 2009
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    In order to arrive at an answer, consider the colour white which is created by mixing red, green and blue. There is no wavelength for white, right?
     
  15. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    thank you, I did not think it would be possible for the wavelengths to change in this way.
    looking at the colour scheme from the 1st page - green, red, and blue are the predominant colours rather than red blue and yellow as I had first thought.
    Where you have mentioned white, - with light would this be completely clear light or is there a white light. presumably daylight is a combination of all visible wavelengths as that is what appears out of it with a prism. Would daylight be considered white light or is this clear light?
     
  16. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    I may have arrived at the wrong answer to mr chips post if there is no wavelength to white may be the wavelengths might merge and change. This is all very interesting is there any more information on this?
     
  17. Alec_t

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    Sep 17, 2013
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    The wavelengths don't change. The additive colour 'wavelength' is subjective, i.e. as interpreted by the viewer's brain.
     
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  18. lotusmoon

    Thread Starter Member

    Jun 14, 2013
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    thank you for that. To get a good untinted white light with GRB, I have 660 in red and 450 in blue. should I be looking for something around 550- 560 in green, as it is half way between or is there another formula to this?
     
  19. Alec_t

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    Sep 17, 2013
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    Personally I would just get whatever was readily/cheaply available. If the resulting 'white' light turns out to be, say, bluish then just reduce the B intensity.
     
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  20. BobTPH

    Active Member

    Jun 5, 2013
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    It shouid be mentioned that mixing of colors will only work if you use a diffuser. Otherwise you will see the individual colors on the boundaries of the lighted area.

    Bob
     
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