Cree XP-G for a 67Gallon Tank - The Planted Tank Forum
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post #1 of 33 (permalink) Old 11-21-2011, 02:31 PM Thread Starter
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Cree XP-G for a 67Gallon Tank

Hi All,

Planning to do a Cree XP-G series LED fixture for my new 67Gallon tank. The tank dimension is 36" L x 18" H x 24" W. Would be using ADA Amazonia Soil as substrate.

Drilled down to XPGWHT-L1-0000-00H51. Max Current capacity is 1500mA. Gives 463 lm @ 1.5A. But planning to drive them at 1A. Viewing angle is 125Deg.

Now the crucial part in choosing the number of LED's required. Planning to use 12 numbers of led. Two rows of led, each having 6 no's. Placing them in 5.5Inch apart. Since the tank depth is only 18inch, would use 60Deg optics.

Are these okay? 12 LED's and 60 Deg optics.

Suggestions please.
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post #2 of 33 (permalink) Old 11-21-2011, 03:10 PM
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12 Xpg's may be enough, depending on the species of plants that you want to grow. 24 Xpg's would definitely provide more than enough light. I would experiment with the optics, as the 60 degree lenses with the spacing you describe, may cause unwanted '"spot lighting". I removed the 60 optics from mine for that very reason, and they were mounted 34" from the substrate.
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post #3 of 33 (permalink) Old 11-21-2011, 05:01 PM Thread Starter
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My fixture is going to be a hanging fixture and would be hung 6" above the water surface. In 18inch tank height, 2" would be covered by the substrate. Hence in effective 18" - 2" (substrate) + 6" (above water surface) = 22" from the substrate.

Do you think that 60 Deg will still give me a spotlight effect?

As far as plants are considered, I am planning to grow HC as the carpet plant, ferns (narrow leaf java fern & Bolbities) and Rotalla.
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post #4 of 33 (permalink) Old 11-21-2011, 05:29 PM
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I used 12 XP-G's with 40 degree lenses on a similar sized tank. Plenty of light. Check out my build thread: https://www.plantedtank.net/forums/di...led-build.html
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post #5 of 33 (permalink) Old 11-21-2011, 05:41 PM
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I think you will get about 120 micromols of PAR with that setup. Raise the light to 12 inches above the top of the tank, and you should get about 90 micromols of PAR. Use a dimmable LED driver and you should then be able to reduce that down to about 40 pretty easily, and that's all the PAR you need. And, you would have no noticeable spotlighting then.

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post #6 of 33 (permalink) Old 11-22-2011, 04:16 AM Thread Starter
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Quote:
Originally Posted by h2oaggie View Post
I used 12 XP-G's with 40 degree lenses on a similar sized tank. Plenty of light. Check out my build thread: https://www.plantedtank.net/forums/di...led-build.html
But my tank is 67 Gallon. So do you think 12 XP-G led's are enough for my tank. Tank length is 3 feet and width is 2 feet. Height = 18inch



Quote:
Originally Posted by Hoppy View Post
I think you will get about 120 micromols of PAR with that setup. Raise the light to 12 inches above the top of the tank, and you should get about 90 micromols of PAR. Use a dimmable LED driver and you should then be able to reduce that down to about 40 pretty easily, and that's all the PAR you need. And, you would have no noticeable spotlighting then.
Hoppy so do you suggest 40 Deg optics and raise the light to 12 inch from the surface of the tank? I would be using CAT4101 driver with dimmable option.

Am still confused on whether to stick to 12 LED's or more.

To calculate the number of LED's required for a tank, can we take the area covered by an LED with a fixed optics (60deg or 40 deg) and see how many led's are required to cover the entire area of the tank?
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post #7 of 33 (permalink) Old 11-22-2011, 11:06 AM
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I am skeptical that 12 XPG's using 40 degree optics will work without having large shadows, but someone here has already said they've tried that on a similarly sized tank and it looks fine.


I'd be more inclined to use 60 degree optics for better spread.


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post #8 of 33 (permalink) Old 11-22-2011, 12:08 PM
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I'm running 10 xml's bare and close to the tank. A rough caluculation would be that each of my leds are putting out twice the light that yours will in your setup.

They are set 6" apart and lighting the front half of my 6'x2'x2' I have no banding problems, just horrible spill if I lift the light higher.

Tank pic:


From my limited experience I would say that your numbers and optics for your tank sound spot on.

(BTW are you considering using a controller for dimming and potentially using different colour strings to tweak the look of your tank? If you are, or may in the future, I'd suggest more LEDs and split them into colour channels, that's phase 3 for my build. It will allow you to run the LED's at lower currents if neccesary but still give you a good overhead if you decide you need more light later. We're still very early in the development of this lighting. Who knows what next weeks 'in' idea will be!)

I'm looking for high/very high growth at the moment. I know Hoppy's philosophy is for more controlled growth, so I've looked to multiply up his LED guestimate PAR figures a touch

create random acts of beauty...
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post #9 of 33 (permalink) Old 11-22-2011, 02:25 PM
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Quote:
But my tank is 67 Gallon. So do you think 12 XP-G led's are enough for my tank. Tank length is 3 feet and width is 2 feet. Height = 18inch
I do. Although your tank is a bit larger in dimensions, I think 12 XP-G's will give satisfactory coverage. I should mention that I am running the LED's in my fixture at roughly half their rated power (~700 mA, compared to 1300+ mA).
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post #10 of 33 (permalink) Old 11-22-2011, 02:39 PM
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Originally Posted by h2oaggie View Post
I do. Although your tank is a bit larger in dimensions, I think 12 XP-G's will give satisfactory coverage. I should mention that I am running the LED's in my fixture at roughly half their rated power (~700 mA, compared to 1300+ mA).
Lol I have so many LEDs over my 45g cube that I can't run them over 300mA without getting algae apocalypse.


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post #11 of 33 (permalink) Old 11-22-2011, 03:31 PM
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I would try to chose optics so the cone of light is all within the top of the tank, with the light striking the glass in the top half of the tank. That minimizes the spillover glare. 60 degree optics should meet that requirement, but 40 degree would make the light miss the glass entirely, and would concentrate the light too much, giving too much PAR. If you use aluminum channel heat sinks, with the LEDs mounted inside the channel, the sides of the channel block a lot of the glare from the LEDs. I have one LED light made that way, and it works well. It would work even better if I had used aluminum channels with 2 inch high legs instead of 1 inch.

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post #12 of 33 (permalink) Old 11-22-2011, 05:33 PM Thread Starter
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That's a pretty good tank with LED's. I have never seen a tank with less number of LED's lighting the tank. XM-L's are very good and the most brightest in the Cree series and could driver till 3A. The reason I didnt go for the XM-L was because the driver I use can drive only max 1A.

I do have the option to increase the LED's as my hood is 13" wide. I do not get these led's in India and purchasing it from US. Currently planning to go for 12 LED's and in future I can increase the led's and Warm white led's too.

@ h2oaggie,

Okay. I am planning to drive the LED's @ 1Amp with dimmable option

@ Hoppy,

I have not seen the kind of heat sink you have mentioned. I had planned to use this kind of heat sink.

.

More PAR: I can grow plants well..
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post #13 of 33 (permalink) Old 11-22-2011, 08:01 PM
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Quote:
Originally Posted by shellydsilva View Post
That's a pretty good tank with LED's. I have never seen a tank with less number of LED's lighting the tank. XM-L's are very good and the most brightest in the Cree series and could driver till 3A. The reason I didnt go for the XM-L was because the driver I use can drive only max 1A.

I do have the option to increase the LED's as my hood is 13" wide. I do not get these led's in India and purchasing it from US. Currently planning to go for 12 LED's and in future I can increase the led's and Warm white led's too.

@ h2oaggie,

Okay. I am planning to drive the LED's @ 1Amp with dimmable option

@ Hoppy,

I have not seen the kind of heat sink you have mentioned. I had planned to use this kind of heat sink.

.

More PAR: I can grow plants well..
Aluminum channel extrusions are standard shapes for extruded aluminum. I get mine from a store that sells surplus metal materials, steel, aluminum, brass, stainless steel, etc. Their prices are absurdly low, making this a great deal for me. The last LED light I made I used a heatsink like what you have, but I attached an aluminum channel to it to get the eye shade effect. That worked very well too:

Hoppy
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post #14 of 33 (permalink) Old 11-22-2011, 09:18 PM
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Quote:
Originally Posted by Hoppy View Post
The last LED light I made I used a heatsink like what you have, but I attached an aluminum channel to it to get the eye shade effect. That worked very well too:
This is a good idea but the union between the C-channel and the heatsink will be a potential weak spot, at least for higher currents--- use of thermal compound between the channel and heatsink will help but it's still a weak link.

I don't know for sure how much it would effect the heatsinking, but I personally wouldn't do it if I were running the LEDs at more than 500mA.


You could replicate this, though, by attaching the LEDs directly to the heatsink, and then screwing some aluminum sheeting to the side of the heatsink, extended down as far as you want/need.


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post #15 of 33 (permalink) Old 11-22-2011, 11:54 PM
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First you flatten the mating surfaces with sandpaper, and polish them well. Then use thermal grease between them. There will be a huge area of contact so thermal issues should be trivial. But, I wouldn't try 3 amps on XM-L's with this.

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