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Horticultural led's

Discussion in 'LEDs and Optoelectronics' started by witsender, Feb 9, 2014.

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  1. witsender

    witsender

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    Dec 12, 2013
    Hi People :)
    We're thinking of buying some led's for use in horticulture and I wondered if anyone on the forum has any useful comments to make about types.
    Thank you
     
  2. mursal

    mursal

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    Dec 13, 2013
    Might I ask what sort of horticulture, legal or bootleg :)
     
  3. flippineck

    flippineck

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    Sep 8, 2013
    at all, in a

    All I can remember from reading up about this subject (in relation to fishtank illumination where I was trying to encourage plant growth) is that in general plants are green because they absorb all wavelengths apart from green, which they reflect. So, stay away from green LEDs and go for ones that emit red and blue for best efficiency of conversion of electricity to plant energy.

    I remember looking at the emission spectrum for some of those high brightness floodlight type LED chips, and realising that some of them did not emit very much of their total energy at all, at a wavelength useable by the plant's photosynthetic machinery. so you have to choose wisely.

    And use a decent power supply that can accurately control the current through the LED, otherwise you'll likely just blow the LED chip in short order

    https://www.google.co.uk/search?q=p...UO8mDhQejxYD4Dw&ved=0CEcQsAQ&biw=1351&bih=715
     
  4. witsender

    witsender

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    Dec 12, 2013
    I should say "No, you may not so ask".
    This question of Mursal's is useless - what reply could they possibly expect?
    (frowny face)
     
  5. Arouse1973

    Arouse1973 Adam

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    Red, Orange and Blue LEDs. Ratio 7:1:1 is sometimes used. Standard 5mm HI clear lens types.
    Adam
     
  6. witsender

    witsender

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    Dec 12, 2013
    Thanks Arouse :)
    I can do all the electronics, I'm sure, including the current driving circuitry, and I can see a horticulturalist about the proper wavelengths and how much energy needs to be available in different parts of the spectrum.
    However I see that the led systems sold for use in horticulture are way high priced, and it occurred to me that if I could just buy the led's as components and bring them into my own circuitry we might get a cheaper result which is just as good.
    However! I don't have the part numbers, and what a hassle it would to sift the entire internet looking for the right power etc...
    So I seek part numbers, and anything else that might be useful.
    Thanks!
    :)
     
    Last edited: Feb 9, 2014
  7. Arouse1973

    Arouse1973 Adam

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    LEDs do vary their wavelength within each colour band so you may need to know the exact wavelength required. The exact power needed is difficult to work out because some plants require less light to grow. Having a quick look into it, plants need anywhere between 5800 and 46000 lumens per meter squared. So if you could find a bright LED which is 5800 lumens per watt, then you will need to supply 1Watt of power to give the required light levels or group lower power LEDs to do the same. 1 candela = 1 lumens if that helps.
    have a look here for an idea of the LEDs you can get.

    http://www.leds.co.uk/products/components/3mm_5mm_smd_leds

    Adam
     
  8. BobK

    BobK

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    If you can find an LED that is 5800 lumens per Watt, don't buy it. The best ones available are in the range of 200 to 300 lumens per Watt.

    Bob
     
  9. witsender

    witsender

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    Dec 12, 2013
    Thanks "Arouse" and "BobK".
    I'm beginning to feel informed!
    :) :) :)
     
  10. Arouse1973

    Arouse1973 Adam

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    Check out CREE. They make some very bright LEDs. The brightest LEDs are the white ones which you don't want. But you could group the lower lumen colour LEDs together to increase the coverage.

    Adam
     
  11. tryppyr

    tryppyr

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    Oct 22, 2013
    I'm curious... are LEDs being considered because they are perceived to be less expensive to operate than, say, full spectrum flourescents? Or is the main property the life span of the LED compared to other illumination types? Or is this experiment triggered by the government ban on incandescent that is leading all light bulb manufacturers to LEDs?

    I ask mainly because it seems to me the more traditional illumination sources provide better light for the purpose than LEDs... better, at least, in the sense that they more closely approximate the light source plants really want.
     
  12. witsender

    witsender

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    Dec 12, 2013
    :)
    Thanks Arouse. I still like BobK's remark though, and I think he has a lot of knowledge and experience.
    Without doing all the hard work required to make an honestly well-researched decision, I can see that if what Bob says is true (no doubt in my mind), my project would necessitate the manufacture of a circuit board carrying tens or more likely hundreds of led's.
    Then, I could buy in a switching PSU I guess, but it would want to be a bit special because led's are current driven, not voltage driven. I'm already getting a guts-ache.
    I've concluded that it's not worth the trouble it would take to build a homemade unit, and I'd rather have someone else responsible for maintenance anyway.
    Thanks, guys. I needed to get to this point.
    :)
     
  13. witsender

    witsender

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    Dec 12, 2013
    Hey tryppyr :)
    A very large proportion of the power poured into most electric circuits winds up as heat.
    Because led's handle quantised packets of light with the specific energies/frequencies required for vision (or in this case horticulture) rather than emit Planck radiation as does a tungten filament bulb, much more of the energy is used to good effect in the led than in the bulb.
    OK ? So for reasons difficult to convey in ordinary language, most of the energy extracted from a current passing through an led is used to see with. We all know how hot tungsten bulbs get.
    Another way to say all this is that the cooler a device runs for a given result, the better the device.
     
  14. BobK

    BobK

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    LEDs are somewhat more efficient than fluorescents, but the main reason for using LEDs is that you can provide only the wavelengths needed by plants. Since plants appear green, this means that they are reflecting all the green light and absorbing the red and blue light. LED grow lights use only red and blue light, whereas a fluorescent, or even the sun for that matter, will peak in the green, which it totally wasted on growing of plants.

    Bob
     
  15. witsender

    witsender

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    Dec 12, 2013
    Ahh!
    We need someone to devise a biological system to take advantage of the uncooperatively emitting Sun?
    A lifeform that used green light would be interesting. Say, green light eating people.
    People would live at about a hundredth of the usual rate of one second per second, because they would be plant-based. They'd wear plant skins and live in caves in the early days, then....
    I wonder what a blue girl would be like.
     
  16. tryppyr

    tryppyr

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    Oct 22, 2013
    Welllll... as a general rule, yes. But with horticulture in particular, a little heat thrown off by the light source isn't necessarily a bad thing. Most plants I know about prefer a warm environment to a cold one.
     
  17. GonzoEngineer

    GonzoEngineer

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    Dec 2, 2011
    If you check the NASA Websites, you will find a wealth of information on what wavelengths and ratios are best for growing plants.
    They spent a lot of tax dollars researching this same subject.
     
  18. witsender

    witsender

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    Dec 12, 2013
    I more often wonder how to cool things, but getting things hot is no trouble. ;)
     
  19. tryppyr

    tryppyr

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    Oct 22, 2013
    Ahhh... you must not live in the frozen tundra like I do. ;)
     
  20. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
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