LED as main light

[chucklez]

I have been dropping in here to catch up with this thread several times a week, so forgive me if I missed this. Did any one take a intensity reading with a LUX meter to see how much light actually penetrates the water?

I think this would be fairly simple to do, take a empty 10g tank, fill it with water, rig up the LED lighting, and take a LUX reading from the bottom of the tank. I would do this, but I dont have the equipment.

[Gomer]

Just a little update that you would all be interested in. For more details in what my PROJECT is....see this thread:
http://www.aquaticplantcentral.com/f...pic.php?p=8060

...but for those that don't really care:

Hurried home and got a first comparison photo. ..it is NOT a fair comparison, jsut a comparison . Waiting on Drivers. Right now using batteries.

Both photos were taken with the same camera conditions. In real life, the light is BRIGHTER than the photos show. I just didn't want to adjust things more than keeping things static.

The top picture is a 7watt Azoo palm light.
The bottom picture is a SINGLE 1watt luxeon star.
The picture is a section of my baby shrimp grow out tank.

Keep in mind also, that equal light intensity (to the eye) isn't the same as equal PAR. An experiment later will tackle that issue.

[Abynum1]

hey gomer, you need to cut and paste all you future posts at plant central and post them here as well.I subscribed to this thread because it's so d@#* interesting! I don't want to miss anything!!!

[Abynum1]

By the way that looks like a very nice set up for baby shrimp.What kind of shrimp you growing in there?

[Gomer]

*L* those are cherry shrimp. ...fresh water

[sfsuphysics]

Hmm that's strange in my photo of my led setup the lights look brighter in the picture than in real life

[Gomer]

that is because I underexposed the picture so that I wouldn't have any over saturation.

[Frisco]

I actually work in this field (optoelectronics/photonics: semiconductor lasers) and don't think LEDs will be in the mainstream in this hobby for at least the next couple years. Despite the fact that LEDs are some of the simplest optoelectronic devices to make (compared to a laser or solar cell for example), they are still pretty immature and have some fundamental limitations, which to me means that they will continue to be largely limited to niche applications like moonlights. The US government is actually dumping huge amount of money to help accelerate research into HB-LEDs (and there has been a number of big improvements in GaN blue LEDs in the last several years due to applications like cell phone backlighting), but manufacturers need to make a major leap in capabilities before being able to displace halides as the best available illumination source for a reef tank. An insider's view, but JMO

[reef-man_d-man]

Frisco makes a good point, owever I am going to jump on the band wagon, I really like the growth and color my corals get with a 20000 K HQI (250 watts) however I dont like having a completely blue tank, so I will be adding back in some red and green light (RGB makes white) to even it out just a bit, I will post pictures and info when I get going on it in the next few days/weeks. I am really interested to see if this works out, I will also have blue led's for moon lighting

[mingzen]

hmm, do corals use green at all? i keep thinking of plants reflect green because they don't absorb it, but maybe the algae in coral uses that wavelength.

or else, couldn't you approximate the RGB white using a few yellow LEDs? i keep thinking they make better use of yellow.

[reef-man_d-man]

not sure, I just knoe the RGB model and that its pretty cut and dry, and the CYM model will change everything, and mixing the, gets hairy, I might try that since the greens are more expensive

[MadTownMax]

I've seen a lot of the recent posts concerning wavelength used by corals, back on the first few pages I posted studies conducted on specifically that, including some done with LEDs.

I'm guessing that some of you that are asking about the wavelengh absorbed by chlorophyl are thinking of using these for planted tanks or refugiums (as I am) - as coral's use much more of the wavelength than the 650-670nm used by chlorophyl - hence the need for white LEDs, not different colors blended togather - it may look white to the human eye, but it will still be peaks of distinct energy wavelenghts - not all that useful for coral's symbiotic algae.

[Frisco]

LED's typically have a gaussian like spectral bandwidth peak with an approximately 20nm full width half max (something on that order, it varies depending on the design of the LED and the process used to make it). As an example, to actually span the 300nm visible spectrum, you'd need ~15 different wavelengths. To really get a close to 'true' white source, you need a 460, 532, and 635 nm sources with very narrow spectral bandwidths (Ie, lasers). The main problem is that each of those wavelengths happens to be incredibly difficult to make.

[robwsup]

Frisco,
What is Epitaxy?

[Gomer]

Def: The growth of the crystals of one mineral on the crystal face of another mineral, such that the crystalline substrates of both minerals have the same structural orientation.

[reef-man_d-man]

I am really not worriede about the corals getting usable wavelength from the LED's (thats what my MH is for) as I have said before I am just using it for human eye apesal

[sandisct]

i think my anemone is splitting..... i can see some of the tentacles splitting... guess they must be pretty happy in the tank...

[reef-man_d-man]

awesome can you get a pic of it?

[Gomer]

had a little time to play in the machine shop today. wired it temp and ran it with a regulated power supply. ..Sorry..didn't have the camera with me..but it sure was nice and bright! I'll work on the 24 LED section later in the week.

Should have my drivers the beginning of next week, and then I'll be able to post comparison pictures of LED vs PC

[Gomer]

view of the heatsink...an overkill, but I got a deal on it. ...hmm...I can switch out to 3watt luxeons on this

[MadTownMax]

Nice work gomer, overkill or not, at least you know it will work, and you could always load that thing up with luxeons until it gets hot, and then you could always attach a fan to it and load on even more

[nepuck]

I have not read the entire thread; has anybody got PAR readings?

[Frisco]

Like Gomer said, the term epitaxy is used because the atoms inside the LED/laser chips all line up in rows, unlike materials like glass which are amorphous and have their atoms randomly distributed. The ordered and predictable placement of the atoms inside the materials are some of the reasons that these things are optically active and can convert electricity efficiently to emit light. For example, with GaAs based materials, the atoms are located in rows every 5.65325 angstoms, and there are a variety of other materials (alloys of Al, In, Ga, As, P, Sb, and N) that can be made to fit this 'atomic template'. Each alloy has slightly different electrical and optical properties, and if you take these different materials and put them together, you can make a device that either emits light (IE, a LED or laser) or absorbs light (photodetector or solar cell). I actually work with the processes by which these materials are deposited - the two main ones these days are Metalorganic Chemical Vapor Deposition (MOCVD) and Molecular Beam Epitaxy (MBE). Although my focus has been GaAs devices, which produce light between 630 and 1060nm, the same concepts and processes are used to make visible and UV devices. In the case of blue LEDs, they use GaN based materials, and their alloys are combinations of In, Ga, Al, and N. GaN has some fundamental limitations because there aren't nearly as many materials to choose from, and the result is that they have a much smaller range of wavelengths that they can make (405nm is the sweet spot for GaN). While you will see people selling longer and shorter wavelength devices, the efficiency, power output, and reliability of the devices takes a big hit. Green is even more difficult to make (you have to use MgZnSSe and similar materials); people play tricks to try to take more conventional GaAs materials and get it to make green but neither approach is horribly practical and manufacturable. Overall, historically that's why you see red LEDs and lasers very often, blue LEDs less commonly, and green very infrequently.

[Gomer]

Nice explaination Frisco :-D

hmm..I wonder if you could do something with LEDs like you do with lasers.... harmonic generation. Wonder how efficiently you could do it with a thin slice of a BBO....?

[sfsuphysics]

Frisco, I learned in my solid state class that when doping semiconductors the doping was more or less a random process and you can't really get the exact distribution you want. Where as you seem to state different, saying that the placement is exact.