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Old 05-12-2011, 08:13 PM   #16
IWANNAGOFAST
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I have 4 XP-e blue's running at 350ma. They don't really cast a noticable blue over the tank but I do notice it on my green neons. With them on the blue is a lot brighter.
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Old 05-12-2011, 08:45 PM   #17
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Quote:
Originally Posted by IWANNAGOFAST View Post
Hoppy, why not lower it and use 60 degree optics? Is the drop in PAR that much? I don't really want to hang my light 2 feet off the tank either, as it is now, it's about 1 foot
When the light is one foot from the water surface and 3 feet from the substrate, the PAR at the top of the tank can be nearly 9 times as high as at the substrate - not that much, but still many times higher. With the light 2 feet from the water and 4 feet from the substrate, the light at the top of the water will be less than 4 times what it is at the substrate. That can aid considerably in avoiding algae.

With 60 degree optics, at 12 inches away from the LED, the light cone will be about 12 inches in diameter, so there will be no spillover over a 24 inch front to back tank. At two feet from the LEDs, the cone will be about 24 inches in diameter, so a little spill over is possible, but not much. With 40 degree optics the cone is about 2/3 that large in diameter, or 8 inches in dia at one foot and 16 inches in dia at two feet - no spillover at all. With the number of LEDs you are using, there will be no noticeable spotlighting at 4 feet, with either 40 or 60 degree optics, but the intensity will be greater with the 40 degree optics because more of the light will directly illuminate the substrate, without first reflecting off the glass, which wastes some of the light.
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Old 05-12-2011, 09:14 PM   #18
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Interesting... I guess this is the method to use to use fewer LEDs right? If one were to use more LEDs, the optics would not be necessary?
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Old 05-12-2011, 11:35 PM   #19
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If it's 4 times less par at the surface wouldn't it be even less at the substrate?

So if the issue with having it so close to the surface (1 foot) is because of the amount of LEDs couldn't I just lower the amount I have? That would save money. Could there be a balance of enough LEDs to cover the footprint of the tank but not too many to have to raise it up higher? I know too few LEDs won't Give me enough par but too many will be algae heaven lol.
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Old 05-13-2011, 01:11 AM   #20
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The problem is that the intensity of the light drops proportional to the square of the distance from the LEDs. That relationship can't be defeated. But, with lots of LEDs, the light source is distributed all over the top of the tank, so as you get closer to the LEDs, the rise in intensity stops going up with the distance squared, since fewer and fewer are illuminating that spot. That means, with just a few LEDs providing all of the light, that inverse square relationship remains valid up to pretty close to the LEDs.

The point you missed is that if you have 50 mms of PAR at the substrate, with both setups - one with the LEDs 1 foot above the tank, and the other with the LEDs 2 feet above the tank - the one with the LEDs closer to the tank has a much higher PAR near the water surface than the one with the LEDs farther from the tank. But, both have 50 mms of PAR at the substrate.

It will work either way, but the higher above the tank the light is, the less variation in PAR from top to bottom of the tank. The sun is 93 million miles away, and the sunlight intensity varies not at all over even a 10 foot distance. But, our lights are typically right at the top of the tank, so the intensity varies a lot over a 2 foot distance.
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Old 05-13-2011, 01:15 AM   #21
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I believe Hoppy is saying that the narrower 40 angle and to a slightly lesser extent the 60 angle optics will drop off less from top to bottom as the beam is spreading less over distance compared to the close up no optics option @ ~120. The narrower optics angle + distance will give you a more uniform PAR level from surface to substrate.

If I ever do a rimless tank, I'll go for the narrow optics and try to illuminate just the tank and not the surrounding area. It would look very nice in a dimmed light viewing room. Sort of like a spotlight on a work of art some people set up track lighting for. Paintings, sculptures, etc.

Edit: looks like Hoppy explained it himself before I could post LOL.
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Old 05-13-2011, 03:30 AM   #22
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Quote:
Originally Posted by audioaficionado View Post
I believe Hoppy is saying that the narrower 40 angle and to a slightly lesser extent the 60 angle optics will drop off less from top to bottom as the beam is spreading less over distance compared to the close up no optics option @ ~120. The narrower optics angle + distance will give you a more uniform PAR level from surface to substrate.

If I ever do a rimless tank, I'll go for the narrow optics and try to illuminate just the tank and not the surrounding area. It would look very nice in a dimmed light viewing room. Sort of like a spotlight on a work of art some people set up track lighting for. Paintings, sculptures, etc.

Edit: looks like Hoppy explained it himself before I could post LOL.
And, the optics don't affect the inverse square relationship. The optics make the PAR at any distance higher than without the optics, but the intensity still follows the inverse square relationship. But, if the light is one inch above the tank, the intensity at the top of the tank will be 100 times that at 10 inches from the light - 10/1 squared. If the light is 10 inches from the top of the tank, the intensity at the top of the tank will be 4 times that 10 inches down in the tank - 20/10 squared.

In my opinion the benefit of the optics is to get more of the LED light directly on the substrate, instead of having half of it reflected off the inside of the glass to the bottom of the tank, where half of the light may be lost.
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Old 05-30-2011, 03:39 AM   #23
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I hope some of you guys are subscribed so you can help out with these next questions:

So Justincgdick and I were going over the led choices I've made so far and we both agree that the lights will be more on the warmer side so I am going to add 6 Royal Blue Led's. I will remove 6 of the Neutral Whites and run the RB with the CB on one row powered by one 48P. Can I do that being that the RB's are XPE's (3.4@700mA) and the NW's are XML's (2.9@700mA)? Or would I need a separate driver for the royals?

First Driver, back of the tank: NW - 3.4 In - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW.
*
6 Inches
*
Second Driver, Center: CW - 3.4 - RB - CW - RB - CW - RB - CW - RB - CW - RB - CW - RB - CW.
*
6 Inches
*
Third Driver, Front: NW - 3.4 In - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW.

40* Optics on everything but the RB's.

How does this look? I would like the lighting temp to be closer to 8000k.

or if I cannot do that then how would this work?

First Driver, back: NW - 3.4 In - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW.
*
* RB 6 Inches RB RB RB
* \ / \ / \ /
Second Driver, Center: NW - 3.4 In - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW.
* / \ / \ / \
* RB 6 Inches RB RB RB
*
Third Driver, Front: NW - 3.4 In - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW - NW - CW.

The Royal Blues will be run on one driver bringing the total to 4 drivers. I'll put those on C channels to save on the price of a heat sink. The Royal Blues will be criss-crossed from one C-channel to the other.
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Old 05-30-2011, 03:51 AM   #24
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SO with the addiction of the 4th driver I decided to add 2 more RB's to bring it up to 8. What do you think about Zig Zagging them?
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Old 05-30-2011, 06:53 PM   #25
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So what do the LED experts think?
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Old 05-30-2011, 07:13 PM   #26
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This is what I had in mind ....



I will space the RB's further apart to be able to reach the sides of the tank which is important but the diagram was thrown together because I tend not to describe things so well.
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Old 05-30-2011, 08:23 PM   #27
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I would wire the blue LEDs so only one wire goes across the middle row, not back and forth. That has no effect on the functioning of the LED array, just makes it neater. I'm still not at all sure what light intensity you will get with this. And, I would put the LEDs on the inside of the channels, not on the outside. That lets the sides of the channels block much of the light from viewers eyes. With high power LEDs that is important.
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Old 05-31-2011, 12:31 AM   #28
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Well the RBs will be the only ones with the C channel, the rest will be using regular heat sinks. I'm not sure how big the sides are, wouldn't it block out some of the spread of the lights?
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Old 05-31-2011, 12:32 AM   #29
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I forgot to mention that I only put those lines to show that those were connected to one driver, although I did think about wiring them that way at first lol.

I'm hoping to get High light with this fixture.
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Old 05-31-2011, 03:25 AM   #30
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If you are using regular finned heatsinks you might want to add some kind of light shields so there is far less chance of someone looking directly at the LEDs. Don't underestimate how bright those little spots of light are.
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