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Thread: LED spectral research

  1. #9
    Av8tor1's Avatar
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    Mike, here is a ref about using the LED as a detector....

    http://www.instructables.com/id/LEDs-as-light-sensors/

    I always thought they would only detect the same wavelength they would produce, that would be easy enough to verify by using a blue LED to check the output of a Red LED etc etc.

  2. #10

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    I did find this philips horticulture catalog with a bunch of case studies, but they are unfortunately short on details:
    http://www.lighting.philips.com/pwc_...ulture-NAM.pdf

    On page 19 a tulip grower says one 35 watt led unit replaced 2 58 watt 60 inch t8 tubes. Assuming that 2.5 of the 14 watt units are roughly equivalent to one 35 watt unit, that suggests 5 lamps per ten square feet to equal 2000 lumens t8/sq foot, or 4 per 2 x 4 foot shelf. I provide a nominal 1600 lumens t12/sq foot to potted plants, which implies an unfortunate 3.2 lamps per shelf to match t12s. But 4 would use a measly 56 watts/shelf, which would be pretty great. At my rates, and in the unlikely event I made no calculation errors, a shelf of 4 t12s (including ballasts) consumes $101.61 of electricity/year, while 4 of these lamps would consume only $28.47, while hopefully actually providing more PAR/sq foot. So lamp cost recovery would occur within the 3 year warranty period, which seems pretty great. Useful lifetime at 12 hrs/day is supposed to be 4.56 years, so there's a substantial expected consumption bonus after the upfront cost is recovered. That's not bad at all, even if one had to finance the upfront cost. Replacing 30 shoplights remains a little daunting for me, but this looks pretty promising. I look forward to your results, I hope 1 lamp will be adequate at least for 2 square feet, if it would do 4 sq feet that would be really compelling.

  3. #11
    Av8tor1's Avatar
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    FWIW,

    I have requested the relative spectral energy data and CCT of the white LEDs in these units from Philips.
    I wont be holding my breath though.... lol

  4. #12
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    As far as I know, you can't make white leds without blue + filter. That's how fluorescent tubes work, too, although they produce UV which is then converted to white light using phosphor. From wikipedia (http://en.wikipedia.org/wiki/Light-e...#White_light):

    There are three main methods of mixing colors to produce white light from an LED:
    - blue LED + green LED + red LED (color mixing; can be used as backlighting for displays)
    - near-UV or UV LED + RGB phosphor (an LED producing light with a wavelength shorter than blue's is used to excite an RGB phosphor)
    - blue LED + yellow phosphor (two complementary colors combine to form white light; more efficient than first two methods and more commonly used)
    Looking for N. Campanulata hybrids. Also would like to grow some nepenthes from seed. Growlist/pic thread: http://www.terraforums.com/forums/sh...-Pete-s-plants

  5. #13
    Av8tor1's Avatar
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    Thanks for the info pmatil,

    Here is a good link from Philips that covers the basics: http://www.lighting.philips.com/pwc_...led-lamps.html

  6. #14
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    I know Andreas has done quite a lot of experimentation with his LEDs. He seems to have gotten them down pretty well, so for those of you on the fence about trying them out, you can always purchase a few meters from him.


    Thanks for the link to these bulbs, Butch. It's something I'll definitely consider down the line. Exciting times.


    Forgot to mention, there have been studies that show far-red light inhibits seedling germination. Consider this when buying your bulbs..
    Last edited by mato; 07-11-2014 at 03:13 PM. Reason: Far-red comment

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