Designing LED Fixture - The Planted Tank Forum
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post #1 of 18 (permalink) Old 10-20-2011, 12:58 PM Thread Starter
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Designing LED Fixture

I have been following the posts regarding DIY LED fixtures and have decided that I want to build one. I have a 40 Long 48"x13"x17" (rounded to the closest whole number). I have a couple of questions regarding light selection that I am hoping somebody will be able to help answer.

I am looking to use CREE XM-L using the 2:1 ratio of Neutral : Cool White. Based on my tank size I was thinking of using 16 bulbs. I figure if this is too many bulbs I can always lower the power. Would 16 be enough bulbs?

Should I use lenses? If so, what degree would be recommended?

I appreciate any advice or lessons learned.

Thanks!
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post #2 of 18 (permalink) Old 10-20-2011, 04:21 PM
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Ok-I'll try to help you out. I've got a few questions though. How do you arrive at a 2 to 1 ratio with 16 emitters? The math doesn't work. You'd need 18 (which should be plenty of light) to get that ratio. 12 neutral whites to 6 cool whites. How much drive current do you intend to use? Have you chosen a particular make/model? They'll need to be dim-able, just in case the emitters are too bright and if you want to adjust the overall color of the lighting.
I don't think you'll need optics, but that depends on how high you mount the completed fixture. Let me know the answers and we'll go from there.
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post #3 of 18 (permalink) Old 10-20-2011, 07:20 PM Thread Starter
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O2surplus, thanks for the response. My bad, you are correct 18 is the number not 16 (wasn’t quite awake when i posted my message). I was planning to buy the meanwell eln-60-48p driver. I do not know on the current at this point, but from what I have read, this driver should be sufficient.
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post #4 of 18 (permalink) Old 10-20-2011, 10:01 PM
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O2surplus gave you some good answers so I'll just add in what I can and agree.


Quote:
Originally Posted by BG1772 View Post
I am looking to use CREE XM-L using the 2:1 ratio of Neutral : Cool White.

Unless you like a tank very "sunny" and "warm" looking, you may want to reverse this and use mostly cool whites. I personally prefer a mix of all neutral whites with some royal blues, but you have to have the royal blues on a separate dimmable driver to make it look right.

Quote:
Based on my tank size I was thinking of using 16 bulbs. I figure if this is too many bulbs I can always lower the power. Would 16 be enough bulbs?
Depends on your drive current. If you have a beefy heatsink (and fan cooled), and a driver that can run the XML's at 2.0 to 3.0 amps, then you could get along just fine with 5-8 of them, really. There are a few drivers that can do this but you have to look around, I don't recall them right off hand.

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Should I use lenses? If so, what degree would be recommended?
Not really needed unless you want to hang the lights up high for easy tank access. In that case, 60 degree optics give you about a 12-15" space between the tank and lights---- 40's will give you 20-30" or more.


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post #5 of 18 (permalink) Old 10-20-2011, 11:48 PM Thread Starter
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Originally Posted by redfishsc View Post
Unless you like a tank very "sunny" and "warm" looking, you may want to reverse this and use mostly cool whites. I personally prefer a mix of all neutral whites with some royal blues, but you have to have the royal blues on a separate dimmable driver to make it look right.
Excellent information redfishsc. I like the idea of adding some blue. I may try a couple of different options to see what color mix I like best.

Thanks again.
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post #6 of 18 (permalink) Old 10-21-2011, 01:25 AM
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Originally Posted by BG1772 View Post
Excellent information redfishsc. I like the idea of adding some blue. I may try a couple of different options to see what color mix I like best.

Thanks again.
Whatever you do, don't make the fixture very "permanent" until you've tested it out and you are thoroughly happy with the color. I have a big array I put up over my 45g and used 4 cyan LEDs that I now hate, and I dread ripping that thing down, taking out the cyans, and putting in something else. So much hassle lol.


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post #7 of 18 (permalink) Old 10-21-2011, 11:40 AM Thread Starter
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My plan was to take the extra time to drill and tap the heatsink to allow me to replace LEDs if I do not like the color combination.

I will be using 2 rows of 9 LEDs. Any advice on how wide of a heatsink I should use? I was thinking of getting a 6" x 42" heatsinc. I am also going to go by my local scrap yard to look for some alternatives to using a pre-made heatsink.
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post #8 of 18 (permalink) Old 10-21-2011, 12:47 PM
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you be using xm-l t5 or t6 ? , alternative pre-made heatsink will be spoil car amps
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post #9 of 18 (permalink) Old 10-21-2011, 12:49 PM Thread Starter
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you be using xm-l t5 or t6 ? , alternative pre-made heatsink will be spoil car amps
I was looking at T5s. Old amps and other things like that is what I am hoping to find at the scrap yard. We have a really good one close to me that had all kinds of scrap metal.
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post #10 of 18 (permalink) Old 10-21-2011, 01:14 PM
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The driver you mention is under powering your XML.
I would suggest to use XP-E or XP-G instead if you are using the ELN 60-48P.
The ELN60-48P is compatible to the Audino, so controller is easy to make.
Tutorial of how to adjust currrent of the XP-E/XP-G with ELN60-48P combination is easily found on the web. XML is not that common. From your post it seem that you are not really an engineer, so I would suggest you to go with the norm and follow simple to tutorials on youtube and such.

So the 13" is your depth (from front to back) and 17" is the height (from top to bottom), correct? If so, when using 18 XP-E drive at about 900ma and using 60 degree lens, you will around 150-200 PAR at the bottom of the tank. The PAR value also depends on the color ration you have for your 2 neutral : 1 cool white, the values will be lower than the ones I suggested.
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post #11 of 18 (permalink) Old 10-21-2011, 01:31 PM Thread Starter
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The driver you mention is under powering your XML.
I would suggest to use XP-E or XP-G instead if you are using the ELN 60-48P.
Thank you for the advice. You are correct, I am not an engineer and have just started reading about the LED setups. At this point, I have not purchased any supplies.

Quote:
Originally Posted by WingoAgency View Post
So the 13" is your depth (from front to back) and 17" is the height (from top to bottom), correct? If so, when using 18 XP-E drive at about 900ma and using 60 degree lens, you will around 150-200 PAR at the bottom of the tank. The PAR value also depends on the color ration you have for your 2 neutral : 1 cool white, the values will be lower than the ones I suggested.
Yes, you are correct, 13" is the depth and 17" is the height. What color combination do you recommend?
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post #12 of 18 (permalink) Old 10-21-2011, 05:21 PM
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Color is matter of personal taste. Hard to give you what can be considered as advise.

Anyway, both neutral white and cool white can grow plants, so for the health aspect, I don't see a problem there. Adjust the ratio to your likings with dimmers. I recommend 1 neutral 2 cool white to start with.

For aesthetics, cooler white usually give red purplish plants a brighter appearance.

A final note, so far all my clients over 3 4 years love the splash of green I added to the sets.




Quote:
Originally Posted by BG1772 View Post
Thank you for the advice. You are correct, I am not an engineer and have just started reading about the LED setups. At this point, I have not purchased any supplies.



Yes, you are correct, 13" is the depth and 17" is the height. What color combination do you recommend?
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post #13 of 18 (permalink) Old 10-21-2011, 09:29 PM
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For what it's worth, driving XML's at 700-1500mA is NOT under-powering an XML. True that it's not driving it at it's full performance, but it actually is running this particular LED in it's most efficient drive current range (700mA), where it hits 160 lumens/watt.

It's also true that the XPG's are cheaper, nearly as efficient (although NOT at 700mA), and quite beautiful.

The XML will give you a touch more light at 700-1000mA than the XPG but not a lot more.


Quote:
Originally Posted by BG1772 View Post
My plan was to take the extra time to drill and tap the heatsink to allow me to replace LEDs if I do not like the color combination.

I will be using 2 rows of 9 LEDs. Any advice on how wide of a heatsink I should use? I was thinking of getting a 6" x 42" heatsinc. I am also going to go by my local scrap yard to look for some alternatives to using a pre-made heatsink.

Drill and tap, very good idea.

If your tank is 13" wide, then you only need a 6" wide heatsink, with the LEDs placed about 1/2" in from the edge in two rows.

Running LEDs at 700-1500mA demands some pretty thick aluminum with fins (and possibly fans). I personally like the Heatsinkusa.com offerings but they are a bit overkill and not cheap.


Lots of folks are using aluminum C-channel, but it will vary in thickness from one style to another---- get stuff that is AT LEAST 3/16" thick. Preferably 1/4" thick.


You really need the thickness/mass of that aluminum to allow for good heat sinking from the LEDs.


Computer CPUs and car amp stuff will work well as long as you can figure out how to mount it


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post #14 of 18 (permalink) Old 10-21-2011, 09:42 PM
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Check out the spectrum from the various colors of XML you are considering. Cool whites vary in colour temperature but the average is around 6500k give or take 500k. Nw are closer to 4000k or so, so give it some thought before you go with a 2:1 ratio.


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post #15 of 18 (permalink) Old 10-21-2011, 10:34 PM
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For a tank only 13 inches front to back, I would use two rows of LEDs with the rows about 5 inches apart. If you use 18 XM-L mixed cool white and neutral white, at 700 mAmps of current, with the LEDs 5 inches apart, 25 inches above the substrate, you should get about 100 micromols of PAR at the substrate - high light, actually too much to live with.

That would be a good design, in my opinion, because you could then easily use the dimmer to lower the PAR as low as 20 micromols, if not lower. So, you would be able to run any usable light level you want. Or, you could raise it another 6 inches, and get about 80 micromols at the substrate, still high light. You would have a very flexible light set-up. Of course, if you wanted to save money, you could use fewer LEDs, and it would still be good.

If you put 60 degree optics on the LEDs, and if you have them that high, it would be a good idea, you would get about 50% higher PAR amounts. This would still be workable, possibly better because you could run just one color LED and still get good light.

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