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Thread: Best flourescent tubes in the 24 inch length.

  1. #1
    Capslock's Avatar
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    OK, so I have my new terrarium up and running in my office. I'm growing nepenthes (albomaringata and truncata) and some drosera at the moment. The tank is just too short for 36" flourescents, so I have four 24in. tubes in there now.

    The question is, what are the best bulbs? I just used what they had at Home Depot, which are three aquarium/grow tubes and one "cool white" tubes, all 20 watt. Is there a particular kind that gives more light? My only concern is that I'm not maximizing the amount of light I'm providing.

    Capslock
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    Tony Paroubek's Avatar
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    Lights are a very complicated subject.

    Basically as I can make it:
    Lumens is the total light output of the bulb in the visible spectrum. This can vary widely even for bulbs of the same watts.
    CRI or color rendition index is a measure of the over all color tone and how accurate it makes colors look compared to sunlight. The higher the number the more accurate the color of a sample under the light. Which gives you a rough idea of how close to natural sunlight the color tone is.

    Kelvin Temperature is another measure of the color tone of the bulb. The higher the number the more blue it is.

    There is another measure.. PAR which measure the amount of photosynthetic active radiation a bulb puts out. See the problem is plants use light at 420nm and 700nm mostly for photosynthesis. The 420 is down at the bottom end of blue and the 700 is red/far red. These wave lengths dont appear all that bright to us. A light bulb can be talored to put out any wave of light and in any amount up to what the bulb can put out based on it's physical limitations (size, watts etc). A plant bulb looks kind of funky because it has lots of light at both 420 and 700nm and not alot in between. So it's way off on what natural sunlight would measure in CRI and Kelvin but high on the PAR value. To the plant it looks really great. On the other hand a warm white light bulb has a high portion of reddish light and very little blue. It is pretty bright to us but to the plant it has a low PAR value and looks pretty dim.

    Without sophisticated equipment you cant really measure PAR value. Odds are you won't find it either from the bulb manufacturers spectral graph. You can check Lumens (the higher the better) CRI (closer to 100 the better because it will be well balanced between red and blue) and Kelvin 5000-6500 or so again so it is well balanced. There are bulbs on the market that produce a larger number of lumens for the same size and wattage compared to the every day cool white. You will pay more for them and odds are you will have to special order them from a lighting store. Is the higher light output worth the extra cost? beats me...

    Here are two pages from Philips:
    The colortone50 and the ultralume50. Both excellent bulbs at 5000k and high CRI. Note the difference in lumens. (I looked up 20watt T12 2' bulbs)


    Colortone 50
    Ultralume50
    For kicks here is a standard coolwhite in the same size/watts for comparison. Note again the Kelvin, CRI and Lumens between the other 2
    coolwhite

    Personally I use the Ultralume50 in my lab.

    Sylvania makes their own line of comperable bulbs.
    Tony
    Is that a Nepenthes in your pocket or you just happy to see me?

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    Capslock's Avatar
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    Thanks Tony! Slowly I'm absorbing what lighting is all about.

    I've run accross another problem in the meantime. I rigged up my own hood for the terrarium using normal Home Depot cheapie light fixtures. I put together my own on/off switch and power cord for them since they just had bare leads coming off the fixtures. I'm using two 2-light fixtures for a total of four bulbs. When I turn the lights on, it seems they have a LOT of trouble starting up. Sometimes they don't seem to want to start at all. And this is all four bulbs. It's almost like they're not getting enough juice. Could I have used too cheap a plug assembly or on/off switch? I can't imagine that would be the case, but I've used several power outlets at home and at work (where the terrarium is), and it's the same. [img]http://www.**********.com/iB_html/non-cgi/emoticons/confused.gif[/img] Are there any electricians out there who can help me out?

    Capslock
    Malo Periculosam Libertatem Quam Quietum Servitium

    My photos are copyright-free and public domain

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    Tony Paroubek's Avatar
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    Sounds like a wiring problem. Perhaps you ran them in series?

    Hot lead from plug goes to 2 wires. One is hotlead for ballast 1 and one is for hotlead for ballast 2. Same for the white neutral wire.


    If this is correct then could be a mismatch between the transformer and the bulbs. IE a preheat type bulb in a rapid start transformer.
    Tony



    Is that a Nepenthes in your pocket or you just happy to see me?

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    Capslock's Avatar
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    Also, is there an online source that anyone knows of for those Ultralume 50s? I hate going shopping!

    Capslock
    Malo Periculosam Libertatem Quam Quietum Servitium

    My photos are copyright-free and public domain

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    Tony,

    I'm at my wit's end on this! They are wired in parallel.

    I'm using two kinds of bulbs, the F20T12/Home Light Cool white from Philips, and the F20T12/Plant & Aquarium bulbs also from Philips. They act the same starting up. The fixtures are the basic units from Home Depot, with the RL TSP-20-TP ballasts. The bulbs are all securely seated. Once I fiddle with them for a while, they go on. I don't know if it's just the time or if I'm actually doing something when I fiddle with them. They don't seem to go on unless I fiddle with them. However, all along, there is a faint glow in the bulbs (all of them), so I know they are seated well in their sockets.

    There are two possibilities as I see it. First, they are not grounded, as my understanding is you don't have to for 24" and under. Would this make any difference? Second, I got a cheap plug unit, and it could, well, I don't know what that could do.

    It's very confusing because both fixtures act exactly the same.

    Capslock
    Malo Periculosam Libertatem Quam Quietum Servitium

    My photos are copyright-free and public domain

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    Capslock's Avatar
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    Incidentally, the ballast says: Rapid start circuit for pre-heat lamps. As if I wasn't confused enough already.

    Capslock
    Malo Periculosam Libertatem Quam Quietum Servitium

    My photos are copyright-free and public domain

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    would Sylvania Gro-Lux Wide Spectrum40 Watt 48 Inch Fluorescent Bulb be okay for drosera?

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