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Thread: Possible LED layout

  1. #17
    For the love of Science! Dragoness's Avatar
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    They do make LED's in different wavelengths of UV. Including UVC, which is primarily used to sanitize anything from aquarium water to toilet seats, as that wavelength is germicidal.

    There are also limitations to how far it is projected from it's source (the bulb). Many LED's with UV can only project the UV about a foot. I believe a spectrometer would help establish how useful that would be in a terrarium.
    Jen- My Grow List: http://www.terraforums.com/forums/sh...00#post1154900
    "Teaching a child not to step on a caterpillar is as valuable to the child as it is to the caterpillar."
    -Bradley Miller-

  2. #18
    Av8tor1's Avatar
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    you also must consider cooling,

    High power LED's require cooling or they begin to lose efficiency (and color shift in the case of white LED's) from the moment they first get hot.... and they do get very hot if you let them.
    Passive or active cooling mitigation is required for long life... each time they get hot, they suffer some permanent damage

    http://support.luxeonstar.com/custom...nk-calculator-

    you will also need some good thermal epoxy if you're going to mount them to the heatsink yourself, etc etc etc.....
    as RSS recommends, be sure you do your homework before you start ordering anything.

    Constant current driver, variable output is nice
    (you will need a VOMa meter to set the output if you don't have one, typically you cant push the far reds as hard as some of the other colors, so they will be the limiting factor current wise)
    proper heatsink (large if passively cooled, plus fan if actively cooled)
    Thermal epoxy
    Aux optics if you choose to use them
    filter capacitor, 2200uf @35vdc is fine (you may or may not use this depending on your power supply)

    Hard part about LED's is keeping them in good shape over the long haul.... .
    You gotta keep em cool
    Last edited by Av8tor1; 07-07-2014 at 09:15 AM.

  3. #19
    Pk93's Avatar
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    Oops, somehow I forgot to mention what type of LEDs Im going to use..
    RSS, I plan on using high powered LEDs (probably Luxeon Rebels or Crees) and mounting them onto the 18" version of this heat sink since it should be reusable if I decide to change the layout of the LEDs, add more, or update the LEDs if/when the need arises.. this heat sink is designed to have the LEDs mounted with screws and thermal grease rather than thermal epoxy.

    Av8tor1, thanks so much for that link, I was wondering how to figure out whether the heat sink I want to use would work effectively.
    I was planning on using this driver since it is made to mount on the heat sink I was also considering; It has two Meanwell LDD series drivers in it, so I will be able to run two different strength currents; the fact that it is dimmable may come in hand if I need to emulate sunrise/sunset down the line.
    I probably won't use optics because they might focus the light too much at the hight I will have my fixture (4-8 inches above the top of my plants).. I would like to have my fixture further away from the top of my plants but Im not sure how to achieve that without hanging the fixture from the ceiling, which wouldn't be ideal for my space..
    I read this thread and am now looking into the custom Luxeon tristars; I think being able to have different LEDs mounted on one star would allow me to include different wavelengths of light and still allow them to blend at the hight I plan on setting my fixture. Are you still using the tristar you ordered? If so, how has it worked so far?

  4. #20
    Av8tor1's Avatar
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    I think you will find 4-8" of height with high power LED's being driven at max is way more than you might expect, even without accessory optics..
    This is where they variable current driver will be of benefit more than emulating a sunrise/sunset effect.

    Looking directly at my tristar for just a few seconds at full power would result in seeing spots and a rather nasty headache. These aren't your run of the mill, ebay/hydro shop/ flying saucer LED's.

    The ones I used are obsolete now I think, HP LED's technology is where computer microprocessor technology was 15-20 yrs ago. What you buy today is obsolete in six months. The ones that replaced mine have a lower junction temperature I think.

    They worked great for low canopy plants, such as sundews, cephs etc.... but more would be needed for heliamphora or nepenthes. Using the close plant to light distance with higher canopy plants resulted in a lot of shading and diffraction. IMHO, you want more distance (tristar to plant and tristar to tristar), and more light sources to prevent these issues.

    Speaking purely for myself, I'm going to wait for the technology to mature a bit more before I spend any serious coin on an LED system. Currently, T5's just work too well in my application.

    They are cool to play with and one day will be the light of choice for me as well
    Last edited by Av8tor1; 07-07-2014 at 05:08 PM.

  5. #21

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    Just to give you some idea of the heat these guys can generate, I'm using a 1.813"(Fins) X .95" X 32" aluminum heatsink. Its a pretty large piece of metal, I have 10 CREE XP-Gs on them and with the dimmers set at 50% they stay room temp, 65%+ and they get really hot fast. I'm talking cooking eggs hot, hospital grade burns. The drivers are 1.3A with the LEDs supporting a max of 1.5A.

    I've pretty much stopped using any LEDs over .750mA, just too much heat to the heatsink for my applications.

    I've avoided the screw-in/thermal route by using thermal pads, double sided thermal tape basically and just love them.

    I've never tried using an LED without a lense so I can't help there. One odd note, the Phillips lenses were so much easier to mount than the CREE lenses. About 1 in 5 of the CREE lenses have excess plastic inside that makes mounting them a pain.

    I started out just playing with them but the results were so nice and the energy usage was so much less than the T5/CFLs I have that I'm replacing all my lighting with LEDs as they burn out. I have some rambling with the math around here somewhere. It is an upfront cost to save over the years, assuming your LEDs make it to the break even point. According to the specs they should easily do that and still have over 50% of there life left.

    I have to agree with AV the LEDs I bought last year already have a new model out.

  6. #22
    Pk93's Avatar
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    Sorry for the super late response!
    Av8tor1, thats what Im afraid of, I don't want to overdo it and fry my plants .. I searched for variable current drivers and I can't seem to find anything for sale (google just gives me constant current drivers)
    Im going to shorten the false bottom in the tank by an inch or two, but Im still figuring out how Im going to raise the fixture higher above the tank.. I think Im going to grow low canopy plants mostly (Utricularia, drosera, and Cephalotus); I'd love to try growing heliamphora again, but the conditions in the terrarium are too lowland for them (as well as epiphytic Utricularia ) I think (temps have stayed between 74 and 78 so far with no drastic drop at night; I don't have a fan set up in the terrarium yet, but I don't think it will really affect the temperature)
    I would be more apprehensive if I were going to build a lamp for anything other than a single 10 gallon terrarium, plus I think it will be a good learning experience.

    RSS, wow, thats pretty crazy, how did your LEDs fare after getting that hot? I still need to figure out how much the heat sink I plan on using can handle (hopefully it will work okay since it utilizes a fan for active cooling; it also comes with enough hardware to mount 37 LED stars, although I have no intention of using that many.)
    Ive run across the thermal pads before and they look really cool, but I want to make my set up as reusable/adjustable as possible (which is why I want to use a heat with a screw and bolt mounting system)
    Thanks for the tip with the lenses, I'll make sure to get the philips lenses if I need them!

    .. Once I figure out if the Heat sink I want is usable, I'll order it, a driver, a power supply, and a couple LEDs to test out over my tank (I'll have to select a test subject, sorry to the plant in advance..) hopefully everything works out okay!
    Last edited by Pk93; 07-13-2014 at 10:24 PM.

  7. #23

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    I've never let them run that hot for more than about 30m total, it was during the initial testing/construction process that I found this out and adjusted my plans accordingly. From my experiences I would never run the 1.5A LEDs over .750 or so, I'd just add more LEDs around that current level, but as I've said in a lot of posts I'm in this for the long run and paying upfront for massive savings later is why I'm buying them.

    I do plan to pick up one of the Current Satellite LED+ premade fixtures to replace an older T5 aquarium fixture that finally burned out so I'll try and get a write-up on that after 6-12m. 600 Lumens, 36 par @ 12", 28 par @ 18", from an 18" 13W fixture. I still need to look up the stats for an 18" T5 to see how much gain/loss I'll be getting.

    I have no fans intended to cool the heatsinks, there are a few fans by the heatsinks but they are intended for the plants not the lighting.

    The Phillips lenses will not fit the CREE LEDs I have, last years model, if you went with CREE ones you have to get CREE mountable lenses.

    Make sure to read through http://www.terraforums.com/forums/sh...ctral-research so much info in the 2nd link.

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