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OT: LED lighting, part 37...

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  • OT: LED lighting, part 37...

    I installed some new LED lighting in my living room. I need to control the colour of light to which I am exposed in an attempt to try to regulate my diurnal sleep cycle. Bright bluish light in the am and sunset colours with no blue at all in the later pm. I have set up a colour scheme on my computer to help with that but I also needed variable colour lighting for the living room, which is where I live and sleep the vast majority of my time. I seem to suffer from what is called "non-24" which is a diurnal sleep cycle that is not 24 hours but usually longer. I cycle around the clock about every 2-3 weeks, sleeping during the day and awake at night about half that time.

    I installed a variable colour LED light strip from DX that has about 30 watts worth of RGB LED emitters, 300 of them over 16 feet. It runs on 12 volts and draws about 2.5 amps. The remote that comes with it is OK but I bought a compatible remote with control module for $7.00. It is the same type remote but has full independent dimming of every colour from full bright to off and also has memory for the dimming setting. The entire setup cost less than $40, not including the 20' strip of aluminum angle. That I got at the local job shop by trading an LED bulb to put in the light fixture of their brand new Haas CNC lathe. I am looking forward to playing with it.

    A few pictures: The strip light can be set to any possible colour and brightness using the dimmer controls. That includes any colour temperature you prefer as "white" light. It does not come with a power supply. The shown night colour is "pure" white. I normally set it to sunset yellow.

    BTW, I am going into town so I won't be answering questions for a few hours.







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  • #2
    I run the same on my Harley. Call them chicken lights. They hold up well. I was thinking the same thing but not sure how to do it. I like your setup and may copy it.

    Thanks for sharing

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    • #3
      Very interesting project!
      Recently I have been playing around with fluorescent tubes in my living room to try to get some more diffuse lighting.

      How is the Color Rendition Index? (which is a measure of how close to blackbody a light source is) With only 3 colors I can't image that it can be that great. I have read that if the CRI is low, things look unnatural due to gaps in the color spectrum. This is the main reason fluorescent lighting doesn't look as good as incandescent or halogen lighting.

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      • #4
        These are RGB LEDs. The colour rendition index is whatever you set it to be. RGB is sufficient to create the entire spectrum closely. There aren't "gaps in the spectrum". The primary additive colours combine to create all the other colours in the spectrum. To start with, green plus red creates yellow, blue plus green creates cyan and red plus blue creates magenta. Vary the proportions and they create any other colour. Keep all three the same luminance and it creates white which is all of the colours. The spectrum of visible light is nearly exactly a full octave in frequency. That makes it possible to create any frequency between the bottom and top of that octave by interference and reinforcement depending on the mix of frequencies. It requires a frequency close to the bottom, the middle and the top which is what RGB is.
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        • #5
          Is there a black light setting?
          nothing like roasting up a good bowl of red bud and breaking out the black sabbath paranoid album...
          neighbors usually cant here cuz i'll be in the basement where I now live...
          Cops are no issue cuz it just got legal in my state...


          that is allot of light for the wattage for sure... im going to be looking into them.
          Last edited by A.K. Boomer; 12-03-2012, 08:39 PM.

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          • #6
            UV LEDs are available but I don't recall seeing them in a light strip. Could well be that I missed them since I wasn't looking for them. The RGB strip I bought is currently by far the best deal at DX. The prices vary all over the place depending on how recent the product is. DX doesn't change the prices when product goes out of date. It's up to you to find the best bang for the buck. That requires knowing something about the actual LEDs used to make the product. The newer they are the more lumens you get per dollar. It pays to look up the data sheets and figure out the lumens per dollar. That is how I determine how good a deal LED lighting is.
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            • #7
              what about the name "cree" --- are they the best to get?
              my bro only buys flashlights with the cree led's in them and says their the best...


              Edit; just thinking about all the stuff Evan builds and have come to the conclusion that he must have one very nice and patient Wife,
              I can just see him handing over weekly updated diagrams on how to operate the house in which they share lol

              Honey, how come there's a micro-switch on your snooze button? --- ughh - don't press that sweetie - it operates the toaster,,, lol
              Last edited by A.K. Boomer; 12-03-2012, 09:41 PM.

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              • #8
                I looked into the CRI issue a little more, and I think my suspicions were correct. RGB clusters can produce any (most?) visible light colors, as appears to the human eye, but because the lights lack certain frequencies, the color rendition of objects will look funny.

                For example, green and red led light can appear to look yellow to the eye, but if there is a real object that only reflects yellow wavelength light, it will look funny under rgb illumination because there is no actual yellow light frequency.

                Here is an article I found written by some artsy French guys talking about how RGB clusters are horrible at making certain colors look good:

                http://www.crcc.cnrs.fr/IMG/pdf/Diod...-Ezrati_en.pdf

                Adding amber to the RGB cluster makes it look less bad.

                However, I am also interested in how you subjectively think things look under this illumination.

                Oh, and I think that's the reason white led's (blue + phosphor) are used for lighting and not rgb clusters. Because the phosphors have a broad spectrum.

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                • #9
                  Originally posted by A.K. Boomer View Post
                  what about the name "cree" --- are they the best to get?
                  my bro only buys flashlights with the cree led's in them and says their the best...
                  yes

                  Disclaimer: cree shareholder

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                  • #10
                    Very timely thread as I've ordered 4 5m rolls of LED light strips for some testing and evaluation purposes around the yard, shop, and house. It's been a couple of weeks so they shouldn't be long.
                    Looks as though I won't be disappointed.
                    Thanks for a sneak preview of what to expect.

                    AK, prices are all over the map for these strips but I have seen ultraviolet LED strips go for about $55 for a 5M strip and approx. $15 for a 1M strip.
                    Definitely more than the single color or RGB strips but they're out there at any rate.
                    Home, down in the valley behind the Red Angus
                    Bad Decisions Make Good Stories

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                    • #11
                      For example, green and red led light can appear to look yellow to the eye, but if there is a real object that only reflects yellow wavelength light, it will look funny under rgb illumination because there is no actual yellow light frequency.
                      Not true. Photons have wave properties. When electromagnetic waves of differing frequencies are mixed they produce a series of harmonics both above and below the fundamental frequencies of the original waves. Photons exhibit this property called constructive interference. This can be precisely simulated with audio wave forms, which I have done to illustrate the principle.

                      Red is accepted to be a wavelength of 650 nm. Green is 510 nm. I created two sine waves of those audio frequencies, 650 hz and 510 hz. Then I mixed them and did a log spectral analysis to see where the peak spectral frequency lies. It is at precisely 590 hz. Not at all coincidentally, 590 nanometres is yellow light. When red and green light are mixed the product is a range of colours with the peak power exactly at yellow. Other colours are also present but the light is seen by the eye as yellow since that is where the greatest spectral power lies. There is no "gap" when RGB colours are mixed. There is however a great deal of misunderstanding by a lot of people online that write on this subject.

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                      • #12
                        hmmm...
                        The principles of constructive interference and etc have to do with phase, and don't change the frequency of light at all. The same way lasers bounce around and interfere all over the place and keep the same color.

                        In think in normal life, light only mixes linearly, i.e. the waves are additive so there is no frequency change either. No sum of sine(a*t) and sine(b*t) will give you any fourier components at sine(c*t).

                        The mixing you are referring to must be some kind of non-linear mixing, where you start getting sine(A*t) * sine(B*t), and then you can start getting new frequencies. Or some kind of non-additive distortion of the waveforms. Also, you did windowing on your fourier transform, so that will also throw frequencies all over the place. Try the same analysis with two signals lasting a much longer time (more periods) and use a more "gentle" window.

                        In short, I don't think reg and green leds can make pure yellow light, even if it looks yellow to the eye.
                        Last edited by beanbag; 12-03-2012, 11:31 PM.

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                        • #13
                          Increasing the resolution on the window just picks out more little peaks that correspond to the various higher harmonics of the waveform. Same thing happens at light frequencies. They aren't "imaginary" resultants. Mixing frequencies results in new frequencies that didn't exist in either original wave form. It does it with sound and it does it with electromagnetic waves like long wave radio, microwaves and with light.

                          The same way lasers and bounce around and interfere all over the place and keep the same color.
                          Of course they keep the same colour if it only interferes with itself. Try it with more than one colour.
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                          • #14
                            wave mechanics aside, I am mostly interested in your opinion on how things look under this lighting. Whether it is similar to natural/incandescent lighting, or whether things, especially skin tones, look "kind of funny".

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                            • #15
                              I used the same type of RGB lights for an outdoor kitchen. Installed them under the counter top ledge to provide some useful accent lighting. Wonderfully adjustable.

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