|10-20-2013 07:02 PM|
This is a lot of information to take in and I commend you on the effort you put forth. My question is, how to really utilize this information? Many websites that talk about planted tanks give plant lighting requirements in watts/gallon. I am not sure how to convert the information I have gathered on my research for my tank to the more appropriate information of using PAR's.
I would like to know more since in my tank certain plants are thriving as others struggle. Im assuming it is a lighting issue, (or at least light penetration to smaller plants.)
|10-16-2013 02:13 PM|
just needs to change few words to make it right in definition on 1st page:
the radiation (light) that is used by plants for photosynthesis.(means plants absorbed photons)
the radiation (light) that could be used by plants for photosynthesis. (means radiation within specified wavelength)
altho i still might be wrong since English is not my native language
|10-16-2013 12:18 PM|
I prefer a simpler one: One PAR equals one micromole of photons between 400 and 700 nm, radiated from a light source point per second.
|10-16-2013 10:05 AM|
i would like to suggest construction for actual photosynthesis prediction device for diy enthusiasts.
to meet photosynthesis curve we need to divide PAR spectrum in several blocks and adjust each blocks contribution to the summar reading.
easy way to do so looks to me is using different kinds of photoresistors insted of photodiode, because photoresistor itself acts as a filter.
the hard(but more accurate) way would be using several photodiodes with selective filters
|10-16-2013 07:47 AM|
from provided link i read PAR=electromagnetic energy between 400 and 700nm (violet to red) per area unit (often 1 square meter) per time unit (usually 1 second) (and not the actual energy consumed in photosynthesis by plant)
going by this definition you obviously can measure it with relatively simple device.
but then again measuring this way you presume that all wavelengths are equally effectively consumed by plant, which obviously is not true.
still, i do admit this method is better for predicting photosynthesis because it leaves out 'human eye filter curve' introduced in lumen definition.
|10-16-2013 06:11 AM|
"professional" PAR meter sensor spectrum, red line is an "ideal" sensor (in A research defined sense, but I do agree, and the curves make obvious, there is error no matter what you do):
See more here:
See this for my thoughts on a $50 filter/sensor..well more like $70ish, unless you can cut the oversize Baader to use w/ multiple sensors. It is the most expensive part.
silicone photo diode...
Baader filter for UV/IR cutoff
and a inverse filter to Si diode curve
won't be perfect.. but none are..
might as well throw in the expensive Li-cor
Baader filter response:
Si photo diode w/ simulated Baader cutoff applied
|10-15-2013 08:42 PM|
I quote PAR definition in the first post: PAR is an acronym for “photosynthetically active radiation” - the radiation (light) that is used by plants for photosynthesis.
Which basically means that to measure PAR by that definition photosynthesis spectrum curve-like filter is a must on given measuring device. And being microwave engineer I can't imagine how one can produce that filter at home in fifty dollar DIY device.
Simple band pass filter is not good enaugh since it will pass green light which is not used for photosynthesis.
the only thing you guys are actually measuring with your devices is relative light loss in aquarium media. And even that is not completely true since water does not block all wavelengths equally
sorry for being an ass
|10-15-2013 03:43 PM|
|10-15-2013 08:24 AM|
|Master Se7eN||Love it! reason 1 why we need changes.... Wait for it....Wait for it....Here is omes...|
|10-14-2013 12:42 PM|
i still dont get HOW can you build a filter that matches photosynthesis spectrum pattern? without such a filter infront of light sensing element in your meter you are only measuring luminous flux converted via math, nothing more.. actually even worse, you might also be measuring infrared heat that has nothing to do with plant growth
what im saying is if particular device does not have protosynthesis spectrum pattern filter infront of it, i can make it read insane numbers of light that actually cant grow anything. one way is to put it under strong pure green LED. the other way is to put it under near/mid infrared emitter. and so on
|10-14-2013 12:07 PM|
So what do you think I should do with this light configuration ? Should I turn on 4 bulb or with the reflector I have I can go with two than three and at the end 4 bulbs ??
|10-09-2013 01:03 PM|
And this is the shot of my light
Like that you can have an idea.
|10-09-2013 12:19 PM|
thanks for your answer !!
the reflector is a single flat panel of high polished aluminum for the 4 bulbs.
I can see only one image of bulb per real bulb and just at the top of that bulb, so the real bulb cover a bit reflection of this image. So I don't think reflector is doing a great job.
Even if the bulb is half the length of the tank, all the tank is covered by light.
let me search for a pictures of the light and I post it. light is hanging at 20" from the substrate.
Thanks again for your answer and your time.
|10-09-2013 04:34 AM|
|Hoppy||The 36 watt PC bulbs are probably only about half as long as the tank, so if you use two of them, they are probably in one end to end row across the top of the tank. If that is true I think you will want to use all 4 bulbs. A lot depends on the shape of the reflector. If it is shaped so you see an image of the bulbs on each side of them, looking up at the bulbs, so it appears that you have 3 times as many bulbs as you really do, then you might have too much light with all 4 bulbs. If not, you will almost certainly not have enough with only the 2 bulbs.|
|10-08-2013 05:05 AM|
|paronaram||"...tomato and chili seedlings..."|
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