March 1, 2013 | #91 |
Tomatovillian™
Join Date: Nov 2012
Location: Ithaca, NY - USDA 5b
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Electrons & ions (charged atoms) collide with gaseous mercury atoms, which then releases UV photons. Since UV light is not within the visible spectrum, the inside of the tube is coated with phosphor, which glows when struck by UV light. The Phosphor does two things... it provides visible light, and depending on the phosphor, does what is called a Stokes shift. Fluorescent tubes output blue light, and by changing the phosphor coating they can "shift" the color toward the red for warmer lights.
Now as to why the bulbs lose brightness over time, the phosphor degrades over time by being constantly bombarded by UV photons. T-8 bulbs have a different type of coating than T12's, and therefore has less loss. The T5 bulbs are even better relative to loss of brightness. Of course the better the coating, the more costly the manufacturing and coating process.
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March 2, 2013 | #92 | |
Tomatovillian™
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I am not a botanist either, just trying to learn and understand this complex subject myself. Here is a link to a PAR study on a bean plant: http://www.ncbi.nlm.nih.gov/pmc/arti...396523/?page=4 The biggest surprise to me has been how efficient photosynthesis is with the green light, even though it is reflected away to a significant extent. This may explain why triphosphor fluorescent tube lights are so great for growing seedlings, even though their main emission band is in the green region. Here is an in-depth article about the role of green light in photosynthesis: http://pcp.oxfordjournals.org/conten....full.pdf+html There sadly seems to be a lot of deliberate misinformation about PAR propagated by the sellers of overpriced LED grow lights. They will pretty much tell you that plants only need a narrow band of blue and a narrow band of red, and some special, secret wavelength that they include in their products but nobody else knows about. As you have mentioned in your posts, different wavelenghts appear to control different stages of plant growth, and plant species differ in their light requirements. This whole subject seems complicated yet intriguing to me. |
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March 2, 2013 | #93 | |
Tomatovillian™
Join Date: Jan 2007
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So you can make a mercury-free, high-efficiency flourescent light by putting uv-emitting leds inside a phosphor? Where the "fail" in MTBF would be "become too dim for the application over time"? edit: Actually, I guess industry already has these: http://upload.wikimedia.org/wikipedi.../62/Br20_1.jpg (Probably more expensive to manufacture than an ordinary flourescent with all of that hardware in there.)
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March 3, 2013 | #94 | |
Tomatovillian™
Join Date: Feb 2013
Location: Western North Carolina
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thank you as well. RWG |
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March 3, 2013 | #95 |
Tomatovillian™
Join Date: Dec 2012
Location: NEPA
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I just built a quick light stand. I bought T-12 fixtures because they were cheap. I'm only using this setup until it gets a little warmer and could use my greenhouse. I bought 2 Sunshine bulbs and 2 regular cheap bulbs. Will they be good enough to get things going? Also using a heat mat.
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March 3, 2013 | #96 |
Tomatovillian™
Join Date: Jun 2012
Location: Illinois, zone 6
Posts: 8,407
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Nice PVC work. You can make it a shelf when you're done.
It looks ok to me, as long as you can keep the cells moist until the seeds sprout. I would put your cell trays in web flats; then you can dunk it in a bin of water easily for watering, and it's easy to move around. The speed at which they sprout will likely be affected by the ambient temperature of the garage, which I assume goes up and down with the outside weather. If your weather is like mine, it's been all over the place lately, 35 and snow today, 60 and sunshine forecast for Saturday. If you happen to have a sunny day and your greenhouse is warm, it would be worth the effort to carry the trays out there just for the day to take advantage of the free heat. |
March 3, 2013 | #97 |
Tomatovillian™
Join Date: Dec 2012
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Thanks Cole.
I do have cell trays, just put the empty tray there for the pic. I didn't glue any of the PVC so I can add a shelf on top. All I have to do is replace the 90 degree elbows on the ends with T connectors. I also used 1" 1/4 PVC instead of 1" to give it more strength. I think I might add one more light to get a better coverage. Does it really matter what type of bulb I use? |
March 4, 2013 | #98 | |
Tomatovillian™
Join Date: Nov 2012
Location: Ithaca, NY - USDA 5b
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Quote:
6500K bulbs for starting seedlings.
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March 4, 2013 | #99 |
Tomatovillian™
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You want cool white or daylight bulbs for seedling growth. Warm white
are less effective for that phase of plant growth. If you are looking at "color temperature" ratings on the packages, look for "6500K".
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March 4, 2013 | #100 |
Tomatovillian™
Join Date: Jun 2012
Location: Illinois, zone 6
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I don't even try without a web flat around the cells:
http://www.growerssupply.com/farm/su...51_109087.html If you get a bin that it fits into, it's an easy way to dunk it for watering. I 'fertigate' with some stinky Alaskan fish ferts. Besides benefits to the plant from bottom watering, it's a lot easier on me. I am trying to make all of my greenhouse benches into flood and drain tables so that I can water a lot of plants quickly. |
March 4, 2013 | #101 |
Tomatovillian™
Join Date: Mar 2011
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Posted link below previously in an older thread so here it is again. Cool white fluorescents work perfectly well for starting seedlings and are usually the cheapest.
http://www.uaf.edu/files/ces/publica.../HGA-00432.pdf
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March 5, 2013 | #102 | |
Tomatovillian™
Join Date: Jun 2012
Location: Zone 7B, MD
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March 5, 2013 | #103 | |
Tomatovillian™
Join Date: Dec 2012
Location: NEPA
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Here is the material list: 2 - 10' (1"1/4 PVC) 6 - T Connectors 4 - 90 degree elbows __________________________________________________ ___________________ Cut lengths for PVC 7 - 19 inches 4 - 24 inches 4 - 3 1/2 inches If you want to add another shelf just replace the 90degree elbows with T Connectors. Also if you want a tray to fit on the shelf cut the 3 center braces at 15 inches instead of 19" Last edited by Wds83; March 6, 2013 at 05:58 AM. |
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March 6, 2013 | #104 | |
Tomatovillian™
Join Date: Jun 2012
Location: Zone 7B, MD
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March 6, 2013 | #105 | |
Tomatovillian™
Join Date: Nov 2012
Location: Ithaca, NY - USDA 5b
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Fluorescent Bulbs are available in 4 basic colors: Warm White = 2800K-3000K Cool White = 4100K Natural = 5000K Daylight = 6500K The Daylight Bulb (6500K) is almost perfect for starting plants inside, since the Blue PAR for foliage and plant growth peaks at about 6600K. For Flowering, the Red PAR peaks at 4300K, so the Cool White is ideal for Flowering and the Red-PAR coverage. The warm White bulb spikes in the IR, and has fair coverage of the Red, though not as good as the cool white for flowering. Both the Cool White (4100K) and the Warm White (3000K) have extremely poor coverage in the Blue portion of PAR. The Daylight Bulb at 5000K is the worst because it peaks at the yellow-green point within the PAR curve, an area of the spectrum which the plant uses very little of that color light.
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