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LED Lighting for orchidbox

Discussion in 'Growing Areas' started by Clusty, Aug 22, 2016.

  1. Clusty

    Clusty Member

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    Hello,

    I scraped together some stray t5ho's for my second orchidbox and unfortunately they are too inefficient and my box is getting way too hot with all the fans in the world.

    Looks at stats, LEDs would be about 4-5x more efficient (lumen/watt) compared to T5HO's, so was pondering building a light stand. Some guy was selling custom built lights and was suggesting 7k lumens is enough, where as I calculated more in the range of 25k, which does not add up.

    When you compare LED and T5HO PAR etc, are they equivalent for equal lumens?
     
  2. naoki

    naoki Well-Known Member

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    Events highest quality LED isn't 4-5x more efficient than fluorescent light. Many cheap ones are slightly better than fluorescent light, and some of those LED strips which you cut them into lengths are less efficient than fluorescent light.

    If your light fixture has to be inside the box, it makes a difference to invest on a good quality LEDs. This is part of the reason I've been going for the best efficiency LEDs (within reasonable cost).

    The amount of lumen you'll need depends on how big your space is.

    The spectra are very different between fluorescent vs white LEDs, but if you don't nit-pick, you can think PPF/lumen or PPFD/fc is somewhat similar. For example, I calculated PPFD/fc from Cree data sheet, and they are 0.15-0.18 (depending on K and CRI). From my measurement, T8 and T5HO gives about 0.14-0.16.
     
  3. Clusty

    Clusty Member

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    Great. So 1 LED Lumen is roughly equal to 1 T5HO lumen.
    The box is 5x3x3 feet. Rough calculation gave me in the 20k range to get about 2k foot candles, is i remember right.
    In fact the lights are outside separated by glass. Problem is boxes are cramped and the top box gets heated a lot from the lower box's light.
     
  4. carl

    carl Active Member

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    Insulation between boxes? A sheet of 1/2" or 3/4" sytrofoam insulation board might help there. You can also run a fan across your lights to bring outside air in for cooling if they're separated from the environments.
     
  5. Clusty

    Clusty Member

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    I thought about the foam thingy.
    That, plus some proper lights should be enough.
     
  6. Marni

    Marni Well-Known Member Staff Member Supporting Member

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    Please show us what you come up with.
     
  7. naoki

    naoki Well-Known Member

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    What kinds of orchids are you targeting? 2000fc of continuous light is very strong for most orchids. You can grow many carnivorous plants with that much. Under the perfect light distribution with no waste, you do need 30000 lumen to cover 15 sqft (1 fc = 1 lumen/sqft) at 2000fc.

    With 5'x3' area, you are right 7000lumen is a bit low end (unless there is no light loss due to reflection etc). But 10000-20000 lumen is probably good amount.

    If you are handy, samsung H-series is amazing (almost 190lm/W). High efficiency means low heat production. It is supposed to be available any time now, and I'm waiting for mine:

    Samsung LT-HB22D 1120x18mm, 4000K, 4040lm, 187lm/W, 22.5V, 960mA, 21.6W, SI-B8T221B2HUS, $34.29 from digikey http://www.digikey.com/product-search/en?keywords=B8T221B2HUS

    1 of this (21.6W) produces similar amount of light as 54W T5HO. 3-4 of these will be perfect for your space. It is a little pricey, though. Samsung inFlux is less efficient (=more heat), but about a half price of H-series.
     
  8. Clusty

    Clusty Member

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    The work in progress will be for cool growing orchids:

    The only true cold grower I have a Cymbidium goeringii.
    I was planning into getting into masdevalias. I always liked them but so far I've been killing a few with the extreme heat.
    I am designing the light for the highest intensity orchids, and am planning to dim down ( From what I've been reading, LED efficiency grows if not ran full throttle ).

    I've been looking at Cree's XP-g3, that boasts 190Lumen/W
    Your modules seem much easier to use. How do you cool it down and how to you drive it ?

    My initial plan was to buy LEDs mounted on star PCB's that I'd glue with thermal to an aluminum heatsink


    PS:
    Here's a shot for my 2 boxes.
    The top one has 4x T5H0's. The lower box's light was an experiment with tubes I had lying around.

    IMG_0931.jpg
     
  9. Ray

    Ray Orchid Iconoclast Supporting Member

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    Cymbidium goeringii is not a cold grower at all. While it can certainly tolerate lower temperatures in winter, I find that they do best when grown reasonably warm - nights no lower than 65°F.
     
  10. Clusty

    Clusty Member

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    Great.
    I usually look at orchidspecies for growing info. I assumed that it's slowly drying because my box is too hot: can approach 30C during the hottest summer days (27dec ambient temperature). Also the grower insisted on very cold winter conditions (if I remember the guy suggested around 15deg winter nights)
     
  11. naoki

    naoki Well-Known Member

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    Yes, COB or array LEDs are much easier than individual LEDs. I think that individual LEDs are quite a bit more expensive if you are not reflowing them by yourself, right?

    If you need dimming, 1x Mean Well LPF-90D-48 matches well with 4x LT-HB-22D
    http://www.meanwell.com/webapp/product/search.aspx?prod=LPF-90D&mws=84A71A9516C6A789
    1.88A with 48V max. So you can connect 2 units in parallel and connect these two in serial. If you don't need to dim, you can get cheaper drivers, I think.

    I'm going to see if I can use aluminum C-channel. Basically it is similar to what I did with Phillips XF-3535L (link here). If you want to go with something better, something like this may be better:
    http://www.heatsinkusa.com/1-000/

    I haven't decided if I mount it with screws or the thermal glue. But I did order FUJIK Silicone Thermal Adhesive. Thermal paste + screw generally gives better heat conduction than thermal adhesive, but adhesive might be good enough. If adhesive is good enough, then it is almost as easy as XF-3535L.
     
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  12. naoki

    naoki Well-Known Member

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    Your enclosure looks very nice! What paint did you use inside? I've been using elastomeric paint (used for roof painting) for the last couple years, but I started to see some peeling problems around the area with continuous contact to water.
     
    Clusty likes this.
  13. Ray

    Ray Orchid Iconoclast Supporting Member

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    That's 15C, right? That's not really cold. A cold grower, in my book, would take nighttime temperatures of 7-10C. I just checked, and Jay's site calls it "cool" at 15C...

    FWIW, I find the Asian cymbs do really well in semi-hydroponic culture. Lots of air to the roots, but always lots of moisture, too.
     
  14. Clusty

    Clusty Member

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    Sorry. I got mixed up cold, cool same difference :)
    Doubt I can ever get 7c in the box. I'd be getting a puddle of water next to my box :)
     
  15. Clusty

    Clusty Member

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    My initial plan was to use glass all over, but got a small heart attack when I saw the price.
    So decided to use melamine all over the place and sealed all the seams with a hefty portion of silicone. In theory melamine is supposed to be waterproof. Will see how does it stand the test of time.
     
  16. Clusty

    Clusty Member

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    This is some great info, thanks a lot. Might make my project much easier/cheaper.
     
  17. Clusty

    Clusty Member

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    About reflowing: saw some fella that used solder paste and heated the star PCB with LED placed roughly on top on a frying pan. Looked easy enough...

    Would it work?
     
  18. Clusty

    Clusty Member

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    One last question: I was planning of driving the elements in series since I want to mix and match the colours (Guess in parallel would cause each elements to draw different currents thus messing up all the constant current thing).
    Good idea?
     
  19. naoki

    naoki Well-Known Member

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    It was probably smarter to use melamine instead of glass. It is better to have reflective surface, so you can reduce the light loss. When I use aquarium for orchids, I surround it by aluminum foil or paper. I think the outer coat of melamine is some kind of plastic, so it probably works well.

    I've never done individual LEDs, other people use oven or hot air gun etc. But I personally think that it is not worth using individual LEDs although I haven't done the cost calculation recently.

    If you can find an appropriate driver, serial driving is probably more robust. But the total forward voltage becomes higher (meaning that you might need more expensive wires). With the Samsung strip, you can mix different K. They use mostly same blue diodes, and the difference in color temp is mainly from the phosphor.
     
  20. carl

    carl Active Member

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    Surface mount components (including ball-grid array components) are attached by placing the components on boards with solder already applied to the board, and running through a bake oven, which causes the solder to flow. You just want to keep the oven a little above the melting point of the solder.