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Thread: 55 gallon DIY LED display build (from groupbuyled.com)

  1. #61
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    One other thing I don't mention enough, but I think plays one of the biggest roles in LED lighting is SHIMMER. This is an old article written before LEDs were used in our hobby, but it is my belief that LEDs do mimic nature in respects to shimmer/prism effect where as other types of lighting do not according to the article. I have experimented on this quite a bit, with my 24 LED light and no surface agitation to cause shimmer the acropora on the sand bed start losing color and polyp extension after a few days, add the 'shimmer' back and it regains color and polyp extension in a day. The tank has the same flow, I just move the power heads and returns 1/2" downwards so it doesn't cause ripples, and I have an overflow box so I don't think it has anything to do with organic buildup on the surface or O2 related variables, I think it is the prism effect that is making the LED light that much more efficient and my PAR testing also shows me this.

    I just tested again to verify and in the center of my tank, 1/2 way down, I get a steady 200 PAR with no surface agitation, when I point the powerhead at the surface I get a range of 170-330 PAR in the same spot, so I am getting over 30% more light at the peaks, couple this with the fact a PAR meter reads 40% lower in the Royal Blue spectrum and the light contains much more of that spectrum than any other type of light, you can see how the 330 PAR peaks in reality can be closer to 600 PAR, which with LED lighting that much PAR can be deadly. There is so many variables to think of.

    http://www.advancedaquarist.com/2006/5/aafeature
    At least one previous report of photosynthetic activity under conditions of artificial glitter lines seems to have indicated an enhancement in the rate of photosynthesis (Walsh and Legendre, 1983). Although an explanation of this apparent contraction is beyond the scope of this article, it should be noted that natural glitter in shallow waters differs considerably in frequency, intensity and prismatic quality from that of artificial glitter.

    Figure 4: Natural glitter lines dance across the surface of a Porites coral in a tide pool in Kahalu'u (Kona), Hawai'i. Note how these glitter lines differ from artificially-generated glitter lines in Figure 2.

    Even when various parameters were manipulated in this experiment (such as water depth, surface agitation and distance between the lamp and water surface), it was not possible to replicate glitter lines as seen in shallow tide pools here in Kona, Hawai'i. Natural glitter lines can produce light pulses about three times that of surface intensity (which is immediately followed by 'de-focused' light resulting in pulses of light intensity much lower than average). See Figure 5 for measurements made with a Spectrum Technologies (Plainfield, Illinois, USA) Watch Dog™ data logger and two PAR sensors (one above water, one below). In no case in this experiment did artificial glitter lines produce the high intensities seen with natural glitter lines (data not shown).

    Figure 5: Light intensities both above and below water in a Hawai'ian tide pool. Various factors (such as wind and tidal water motion, among others) affect the focusing effect and hence light intensity of the glitter lines. Underwater light intensity at about 7 cm depth can be briefly almost 3X that of surface light intensity due to glitter lines. By the same token, light intensity can be dramatically lower due to de-focusing of light by wave action.

    The lack of differences in photosynthetic yield under artificial glitter in the present experiment is fairly easy to explain. Since yield at each light intensity was initially measured with 'calm' (i.e., no artificial agitation, hence 'no glitter') conditions and moments later 'with agitation', it was easy to determine the high and low photosynthetically active radiation amplitudes. The average PAR value of glitter lines measured over short periods (a minute or two) always very closely equaled the PAR measured when a condition of 'no glitter' prevailed. In other words, the average intensity of the light field produced by glitter lines over a few seconds' time cannot possibly exceed the average light intensity in a 'no glitter' condition under the same set of circumstances. One may wonder why photosynthetic yield, instead of electron transport rate (ETR), was used to compare effects. The answer is quite simple – computation of ETR requires a known PAR value be used in the equation, and this was not possible in the conditions of this experiment. The PAM 210 does not include a PAR meter (more expensive models do have an internal PAR meter) and it was not possible to synchronize instantaneous recordings of Yield and PAR (a measured with my Li-Cor quantum meter) in a highly variable light yield such as that seen 'with' glitter lines. In addition, one should not confuse the drop in yield in Figure 3 as Photoinhibition. It is natural for photosynthetic yield to drop with increasing light intensity.

    The real question is whether the high light amplitudes produced by artificial glitter lines would encourage a 'ramping up' of photosynthesis able to maintain a higher rate of photosynthesis during the brief (and inevitable) lower light intensities sure to follow the bright 'flicker'. This report suggests it does not. The story may be different with 'real' glitter lines in nature, or in aquaria capable of generating larger waves with high frequency (which could approximate the waves seen in the observed tide pools). For now, it seems that glitter lines are more 'show' than 'go' (photosynthetically speaking) in most aquaria situations.

  2. #62
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    This is a well known phenomenon, there have been studies that investigated 'flashing' and photosynthetic efficiency gong back to the 1930s, when they discovered that if you flash light at a 1kHz rate you get the same production as constant light. Later studies revealed that the dark period can be 10x as long as the light period and still result in the same production. Anyone who has been to a pool in the summer on a sunny day has seen these "glitter lines". These are essentially performing the "flashing" effect. I have discussed this on other thread, but essentially think of it like the light causing part A of the process to fill a 'bucket' and the dark period allowing a secondary process (strangely enough referred to as the "dark cycle") to 'empty' the bucket. If there is constant light, the bucket can only 'spill over'.

    With respect to corals, there have been specific studies that have investigated this effect, many of them, and the above referenced article I'm sure was pointing to one of those studies. These 'glitter lines' are the result of point-source light (sun) and in our tanks this is one reason why people love MH so much (point source) and why LEDs are so attractive.

    With the speed of technological advancement of LEDs, it's likely that the average user is going to 'get burned' by following a 'guideline' that is only 6 months old, but they are using newer style LEDs. That's the trouble with technology advancing so fast!

    http://reefbuilders.com/2012/12/11/x...erforming-led/

    on a side note, w/r to scrubber and LED lighting, we are likely already getting this flashing/glitter effect both in waterfall and upflow scrubbers due to the motion of the water and bubbles, respectively.

  3. #63
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    The big difference here though is 'the studies have shown in the past that shimmer in nature is not equal to shimmer from a MH light'. Shimmer from a MH is just cosmetic, it doesn't provide anything useful according to the studies and my own testing with a PAR meter. This is where I think LEDs differ because it is a much tighter point of light than a MH and LOTS of them. In the beginning days of LEDs people always complained about the 'disco effect' when they spaced their different colored LEDs too far apart from each other and they didn't blend well (I experienced this myself and quickly fixed it so my sandbed didn't look like a 3D movie). Compared to any other type of light, I still get a slight disco effect, but it no longer looks like a rainbow/prism on the sand bed after getting the correct spacing and optics for my setup.

    I just don't think people realize this aspect because it isn't really talked about, but with LEDs, surface agitation is a big factor to take into consideration in regards to amount of light and placement of corals. If you measure a new LED light 12" above in open air and then put it over a tank with agitation the PAR readings will be quite different, and shockingly to most, it will actually be higher 12" under water during peaks vs 12" in open air (more so the tighter the optics you use and closer to the surface you place the light). This can't be said for MH because MH is a much larger point of light and radiates out 360 degrees and needs reflectors to focus the light down.

  4. #64
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    Interesting. I was planning on building an array of fixtures that had a ratio of 5 RBs : 1 CW : 1 NW : 1 WW 2700K : 1 WW 4000K : 1 Green : 1 true violet : 1 Cool Blue : 1 Cyan-Turquoise. Going to have 6 sets of each (30 RBs and 6 of everything else), and I have 6 small Maker's heat sinks so I am going to create "pods". Each color will be on a separate channel (lots of wires!!). I have a bunch of those DIY LED driver boards from TheFishMan65 on RC, each can drive 8 strings of 6 LEDs and can be configured for up to 8 channel PWM dimming (but will probably only do 4 or 6 at the most) and I have an Arduino to control it all. The idea was to be able to test different bandwidths for color rendering. I was planning to group the LEDs very tightly together to prevent exactly what you're talking about with the disco effect.

  5. #65

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    Just cost myself 30 euro i think wired up 10 ww leds but not working and my cw strip does. I tested them with an led test on a multimeter and they light up so im not sure the driver definately works as the solderless cw rig works. This is my first diy solder atempt i normally buy solderless. :-(

  6. #66

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    Great all is working had them wired wrong and badly floyd gave me some soldering advice and its up and running. My clownfish look mental with those luxeon 2700k leds im well impressed thanks for the recommendation joel washed out look is gone :-)

  7. #67

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    Crash im glad you liked it, the 2700k warm whites really seem to help the color depth and gradients dont they?

    Ace, have you seen the vitamin c and light post i have up yet? If so any thoughts? I am also curious how much the benificial shimmer effect is lost on my tank with no optics and the LEDS being less then 5" off the waterline.

    Floyd, that setup would be good for a testing or demonstration piece, but before actually building a full sized fixture, I would suggest trying out the 4 royal blue : 2 2700K- 4000k warm whites (maybe one of each) : 1 true violet. Warmer whites bring out colors better but the light itself looks visibly dimmer, cooler whites make things looked washed out but the light looks visibly brighter. Considering that you service local businesses you would probably pick your whites ratio based not only on "optimal" but also take into account ambient light and desired atmosphere. IE 2700k warm whites would look great in a dimly lit resturant, but for a brightly lit dentists office with lots of windows you would probably want mostly 4000k-6500k whites with maybe even a few cool whites tossed in.

    Also you should take a look at steves drivers, I have heard great things and they are made to be about as plug and play as it gets with aurdinio. They were designed for that purpose.

  8. #68
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    The ones made by thefishman65 are CAT4101 drivers just like Steve's (in fact, it looks to me like Steve copied them) and are 8 channels instead of 4 and cost $50 each

  9. #69
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    There is a looooong DIY driver thread on RC that shows the development of the CAT 4101 based driver. I'll have to take a few pics of the boards I got and post them. PWM dimmable and all

  10. #70

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    Quote Originally Posted by Floyd R Turbo View Post
    There is a looooong DIY driver thread on RC that shows the development of the CAT 4101 based driver. I'll have to take a few pics of the boards I got and post them. PWM dimmable and all
    Awesome, I will have to look into that.... I bought invotronics drivers for my setup, and while they work fine I would eventually like to step up 1000mA PWM drivers. I think that with my current heatsink+leds and 7-10 true violets (probably just driven on one of my 700mA invotronics drivers) should be more then enough for a 48x24 120 gallon tank.

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