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Ok just trying to apply it it to my tank as well but thanks for the clarification very helpful.
Ichthyoid (Bill)-Riddle me this LED question please!
- Thread starter acroholic
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Where the existing 3 lights are already evenly distributed over a plane and with somewhat overlapping patterns, and the planes of the lights and tank bottom are parallel, and at a distance that exceeds the light separation, the difference between 3 @ 100% and 4 @ 75% should be pretty close, but it also depends on the distribution pattern. (eg-parabolic, normal, whatever).
It is for this reason that LED's do not adhere to the 'inverse square law'. There is a modified ISL for them.
<span style="font-family: SymbolMT"><span style="font-size: 14px"><span style="font-family: SymbolMT"><span style="font-size: 14px"><font size="2"><!-- gcu-updated --><font size="2"><!-- gcu-updated --><p style="text-align:left">the modified inverse-square law
</span></span></span></span><span style="font-family: SymbolMT"><span style="font-size: 14px"><span style="font-family: SymbolMT"><span style="font-size: 14px"><p style="text-align:left"></span></span></span></span><span style="font-family: SymbolMT"><span style="font-size: 12px"><span style="font-family: SymbolMT"><span style="font-size: 12px">
</span></span></span></span><p style="text-align:left">Ev = I/(d+delta*d)^2 + r1^2 + r2^2
http://www.pmodwrc.ch/newrad2005/pdfabstracts/Newrad044.pdf">http://www.pmodwrc.ch/newrad2005/pdfabstracts/Newrad044.pdf</a>
</font><!-- gcu-updated SIZE -->[/FONT]</font><!-- gcu-updated SIZE -->[/FONT]
It also depends on the dimensions involved. The higher you go, or the closer the spacing, the less the difference. At infinite distance and/or minimal spacing, they behave as a point source.
I was trying to keep it simple, so maybe we can just break out the PAR meters for proof.
:doh:
It is for this reason that LED's do not adhere to the 'inverse square law'. There is a modified ISL for them.
<span style="font-family: SymbolMT"><span style="font-size: 14px"><span style="font-family: SymbolMT"><span style="font-size: 14px"><font size="2"><!-- gcu-updated --><font size="2"><!-- gcu-updated --><p style="text-align:left">the modified inverse-square law
</span></span></span></span><span style="font-family: SymbolMT"><span style="font-size: 14px"><span style="font-family: SymbolMT"><span style="font-size: 14px"><p style="text-align:left"></span></span></span></span><span style="font-family: SymbolMT"><span style="font-size: 12px"><span style="font-family: SymbolMT"><span style="font-size: 12px">
</span></span></span></span><p style="text-align:left">Ev = I/(d+delta*d)^2 + r1^2 + r2^2
http://www.pmodwrc.ch/newrad2005/pdfabstracts/Newrad044.pdf">http://www.pmodwrc.ch/newrad2005/pdfabstracts/Newrad044.pdf</a>
</font><!-- gcu-updated SIZE -->[/FONT]</font><!-- gcu-updated SIZE -->[/FONT]
It also depends on the dimensions involved. The higher you go, or the closer the spacing, the less the difference. At infinite distance and/or minimal spacing, they behave as a point source.
I was trying to keep it simple, so maybe we can just break out the PAR meters for proof.
:doh:
Ah - thanks for the clarification. As I was typing that, I was wondering if the ISL applies to LED fixtures, given that they're made up of multiple, distinct light sources.
In the end, it sounds like the best bet is to use a PAR meter, although it's still an interesting exercise to figure it out mathematically...
In the end, it sounds like the best bet is to use a PAR meter, although it's still an interesting exercise to figure it out mathematically...
Quiet one-
There are others on here that have experience with the lesser priced LED fixtures made in China. I have seen a 120 watt over a 60 gallon cube that appeared to be working well. I did not see any PAR #'s for it, however. FWIW- I have a 180 W LED that pumps out 250-300 PAR at 24 inches.
Bottom line-
I would be in favor trying one of those ebay sub $200 type 120W LED's with 2 x 24 or 32 W T5's to supplement with Actinic(420nM/purple) bulbs. I have T5 endcaps, a ballast and reflectors I will give you, if you are interested in pursuing this (because you are a student).
The relatively shallow depth of the 40B would be good to use with one of these LED's. They are not optimized for deeper tanks, according to testing I reviewed from among others, Sanjay Joshi.
Here are the results of the Reef fanatic fixture, which is similar to others of this typr LED, I would imagine. As you can see, it would be marginal at 18", but with a little T5 to help round out the spectrum and PAR, I think it would be fine.
http://www.advancedaquarist.com/2011/8/aafeature">http://www.advancedaquarist.com/2011/8/aafeature</a>
Otherwise, wait a year like the rest of us. :doh:
Also, I forgot to ask! What are you looking to grow, coral wise?
gerd = gastroesophageal reflux disease.
I see surgery for it almost every day and would prefer to not be called that.
uke:
Edit:
:shades:
I see surgery for it almost every day and would prefer to not be called that.
uke:Edit:
rdnelson99;703459 wrote: I have a somewhat related question. How many pairs of black horn rimmed glasses with athletic tape on the nose bridge do you think were involved in this thread?
:shades:
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