LED Build for a 48"x18"x18"
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Old 01-25-2013, 03:18 AM   #1
GDominy
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LED Build for a 48"x18"x18"


Well, I took a break from plants for a few years while I was heavily into reef tanks, but Im back.

I am planning on building a new LED array using recycled parts from my 265 Gallon reef, squished down into a rimless 48x18x18 tank and was hoping for some practical feedback. Keep in mind I already have these LED's but am simply mounting them on a new fixture, but am open to the idea of changing out strings of them over time.

LED's will be mounted to a pair of 6" x 20" tapped heatsinks from RapidLED, and the heatsinks will be hidden in a suspended wooden frame (to match the stand) from the ceiling. Each heatsink holds 36 LED's in four rows of nine. Pattern will be 2 x White, 1 x Blue staggered by one LED every row.

W W B W W B W W B
W B W W B W W B W
B W W B W W B W W
W W B W W B W W B


In this arrangement when the two heatsinks are placed next to each other the pattern continues for ever coverage.

I hope to hang the fixture about 12" over the tank, which will give me about 26" between the emitters and the substrate, and will be using 60 degree optics.

The idea is to run 48 Cree XP-G Cool Whites and 24 Cree XP-E Royal Blues (simply to balance out the heavy yellow appearance of the XPG's and will probably be running very, very low mA).

I'll be driving all 72 LED's using 6 x Meanwell ELN-60-48D's (I already own them) and my profilux III will control the dimming (already have the ballast control boards for this as well).

With this many LED's I will be actively cooling the heatsinks with speed controlled fans (profilux will speed the fans up as intensity increases on the LED's).

I have built 7 LED fixtures for saltwater aquariums so I'm pretty comfortable with the assembly end of things, but the last time I was doing planted aquaria I was still using power compact bulbs or T5's.

I would like to achieve par values at 100 (or a touch more) at the substrate which I think I should be able to do at around 750-900mA out of the driver based on the LED spacing (keep in mind it will be actively cooled). I'll be dosing CO2 heavily, already have all my CO2 gear prepped and will be using a Profilux 4 Pump Dosing pump to dose my ferts automatically every day.

I know that this is probably too blue, but I think I am more inclined to swap out 24 of the Cool whites for Neutral or warm whites while maintaining the blues to balance the colours out (just at a lower power).

I haven't been able to find too many build threads for 18" or wider tanks using LED's so I"m a bit concerned about coverage (it has been several years since I have been active on the forum). I am hoping that with this dense pattern I will be able to cover the front and back of the aquarium pretty evenly (I can raise the fixture and turn up the power if need be, the drivers for my XP-Gs are dialled in to max out at 1100mA at 100%).

I guess I don't have specific questions exactly, but really would love to hear from other LED Diy folks

Sorry if this turned into a ramble, Ive been churning through ideas like a madman for a couple of weeks and this is what Ive managed to come up with so far. Once the details are hammered out I'll start a build thread.
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Old 01-25-2013, 07:58 PM   #2
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People who switch from reef tanks to planted tanks are very likely to want to use too much light. My guess is that you will have more light than you will be able to manage. I think you will be running the LEDs at around 300 mAmps to get 100 micromols of PAR at 26 inches. But, 100 is very high light for a planted tank. An easier to manage light level would be around 60, and that would require closer to 200 mAmps, a very low current for the XP-G LEDs.
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Old 01-25-2013, 09:10 PM   #3
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Originally Posted by Hoppy View Post
People who switch from reef tanks to planted tanks are very likely to want to use too much light. My guess is that you will have more light than you will be able to manage. I think you will be running the LEDs at around 300 mAmps to get 100 micromols of PAR at 26 inches. But, 100 is very high light for a planted tank. An easier to manage light level would be around 60, and that would require closer to 200 mAmps, a very low current for the XP-G LEDs.
I must have completely screwed up the calculator when I did the math last night, I thought I was going to need around 650mA to get a PAR just over 100 at that depth.

I have kept planted tanks with extreme lighting before, so I am somewhat prepared for the incredibly delicate balance its going to be, Ill be managing nutrients and CO2 with my Profilux so I can precisely control my levels but I do expect a few months of hell to get things dialed in right. There is no way I would be able to keep on top of it manually.

I can always switch to a wider set of optics too, I have to order these so I could switch to an 80 for better coverage/less intensity. I'm currently running 108 Cree XPG/E's over my 3x2x2 Reef with no optics about 26" off the surface so I guess Im still thinking in reef mode... I could always skip optics altogether but I was really hoping to keep my light spillover to a minimum.

Appreciate your feedback, thank you!
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Old 01-25-2013, 09:37 PM   #4
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Good lord, I dont know what I was thinking last night. I just re-ran my numbers through your spreadsheet and have a way different result then what I was looking at last night. I'm definitely going to have to run without optics to keep a reasonably lower level of light. This is a plus though as it will keep the fans quieter.

The idea with this rig is that the LEDs are going to dim from 0% to 100% then back down to 0% over the course of a day. This way if they do throw over 100 umol then it will only be for a short period, while the rest of the day will be a more modest level.

Try not to look at this as a constant high light rig, its most likely going to be more moderate-high light tank for most of the day, with just a couple of hours of intense peaking.
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Old 01-25-2013, 10:41 PM   #5
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Hey Gareth, nice to see ya back!
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Old 01-25-2013, 11:04 PM   #6
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From what I have experienced you can't run LEDs from zero current to maximum current. They go off at some low current, well above zero. Maybe with some LED drivers it would work, but I couldn't make it do that with the Meanwell drivers.
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Old 01-26-2013, 12:53 AM   #7
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Originally Posted by Hoppy View Post
From what I have experienced you can't run LEDs from zero current to maximum current. They go off at some low current, well above zero. Maybe with some LED drivers it would work, but I couldn't make it do that with the Meanwell drivers.
The Meanwell drivers will only power on at approximately 120mA-150mA (I have tested this with my current set). The Profilux allows me to define to minimum "start" period of the ramp at a certain level so I usually start the dimming at approximately 150mA and will ramp it up to about 500-600mA at peak.

Its a bit frustrating, but I'll take it, I will still be able to program some nice visual effects with the LED's with that range.
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Old 01-26-2013, 12:53 AM   #8
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Hey Gareth, nice to see ya back!
Thanks :-) It has been a while, but I'm back in full swing!
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Old 02-24-2013, 09:31 PM   #9
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Well, decided against using new heatsinks, and managed to come up with an arrangement that I think will work over the new tank... Its bright :-)

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