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Discussion Starter · #1 ·
So I am in the process of building a led fixture to replace my old t5 HO lighting. There is a lot of information out there but some of it contradicts itself so I now have a few questions.
My tank is a 72Lx24Wx30D low tech setup so according to one website I read all I need to do is multiply length times width divided by 22 which gives me a total of 72 leds, does that seem right? Im not looking for anything more then medium lighting.
Having said that, could I get away with 1 watt led or due to the depth of the tank (30inches) would it be better to go to 3 watt?
Thanks for any help or advice you folks can give.
 

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So I am in the process of building a led fixture to replace my old t5 HO lighting. There is a lot of information out there but some of it contradicts itself so I now have a few questions.
My tank is a 72Lx24Wx30D low tech setup so according to one website I read all I need to do is multiply length times width divided by 22 which gives me a total of 72 leds, does that seem right? Im not looking for anything more then medium lighting.
Having said that, could I get away with 1 watt led or due to the depth of the tank (30inches) would it be better to go to 3 watt?
Thanks for any help or advice you folks can give.

ODDLY enough my new 40b build follows your "rule".. funny.
As to suggestions.. First I'd consider using optics for that depth. Second, and more a personal opinion.. pick 1 or 3 w depending on manuf of LED's.
Some 1W put out as much light as 3w and under/over driving either can make a big difference..That is one of the reasons there is so much contradiction...
So optics and led specs regardless of wattage is most important in your case AFAICT.

Then there is individual differences if you just go "generic" LED's. It is messy to say the least..

I know my instinct is to just go 3W since the cost diff is probably minimal. but consider dimming.
 

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Discussion Starter · #3 ·
Yeah I was planning on making them dimming and I think 60 degree optics. I will probably go with Cree because they are a known brand name but there are a lot of chinese knock offs out there for cheap on ebay soo.. I dunno lol
 

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If you are using different wavelength LEDs, I'd definitely go with optics wider than 60*. The colors will not blend well even if the LEDs are right next to each other unless the fixture is raised quite a bit.
If all the LEDs are the same, then you should be fine. I have some cheap Chinese screw-in LEDs that I tried for a little saltwater cube vase. The coverage was good, but the colors do not blend well, I get areas of white and areas of blue.
 

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Discussion Starter · #9 ·
Ok, some good information on this thread. Thanks guys. What is the deal with colored leds? I have read that they are kind of a gimmick because white led's are composed of a full spectrum of colors. But other people say red green and blue can help make colors of fish and plants "pop" like I said there is a lot of contradictory info out there.
 

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Really arent I just trying to find the highest CRI combination possible?

first as to "white" LED's being "full spectrum" well not quite.


As to CRI.. Again personally it is not that important..
since this as a "planted tank" forum.. Colored LED's are not "gimmicks" anymore than this hort. light is a gimmick..


in a sense it may be "splitting hairs" but some do like that.. ;)


http://www.econoluxindustries.com/Technology.html

So w/ "colored" LEDs you can maximise plant needs and add enough to fill the gap in "white" LEds and approx. whatever color you find "pleasing"..warm to cool.. ect.
A common complaint I hear is white LEd's are "flat" or too "blue", or just off.. in a DIY all those conditions can be met to any personal opinion.. esp. w/ dimming on various channel..

Is it needed or a requirement.. certainly not..
One "issue" that is finally addressed is that most LED's .. due to "economics" were orig. targeted to the Reef market..and oddly enough even now reefers are coming around to adding "color" .. like lime or green or cyan or 660nm red..

The 2 are converging but maintaining a difference..it is quite funny.......
CHANNEL ONE:
4 White
10 White
2 Red
2 Cyan
1 Yellow/Orange

CHANNEL TWO:
15 Royal Blue
4 Violet

CHANNEL THREE:
2 Blue

Total 19 LEDs
@ 6500K Kelvin
@ 14K Kelvin
@ 660 NM
@ 520 NM
@ 580-595 NM
Total 19 LEDs
@ 455 NM
@ 410 NM

Total 2 LEDs
@ 460 NM
http://reefradiance.com/lumentek-pro-120.html
 

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Discussion Starter · #12 ·
ok so I think I am going to go with 4 rows of 17 led's with a 2-1 ratio of cool white to warm white with a few red, blue and cyan distributed evenly throughout. I am having trouble finding optics for the emitters though, they all come with 115-120 degrees lenses which seems to me to be way to wide, I was hoping for something closer to 90 degrees. does anybody know where to get just the optics for these led's?
Also as usual any constructive criticism or advice would be great.
cheers.
 

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ok so I think I am going to go with 4 rows of 17 led's with a 2-1 ratio of cool white to warm white with a few red, blue and cyan distributed evenly throughout. I am having trouble finding optics for the emitters though, they all come with 115-120 degrees lenses which seems to me to be way to wide, I was hoping for something closer to 90 degrees. does anybody know where to get just the optics for these led's?
Also as usual any constructive criticism or advice would be great.
cheers.

There are a lot of lenses for LED's..
http://www.ledlink-optics.com/ProductsListLed.aspx?ID=96F3399E0F0E46B29DF525EADADBA406

17 series LED's will need a 54-65V DC out ps if using seperate power/ drivers like the LDD series..

W/ combo drivers (ps/driver one unit) that would be 51-62V
 

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Discussion Starter · #15 ·
Ok so I have the led's, drivers, power supply and heat sink. To secure the led's to the heatsink I have 2 bottles of Arctic Alumina thermal adhesive. But it doesn't tell me how much I should be using on each individual star, should I use just a drop? Do the stars have to sit Perfectly flat on the Heatsink or can they be a little off? Anyone with some experience with this stuff please feel free to chime in.
 

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Ok so I have the led's, drivers, power supply and heat sink. To secure the led's to the heatsink I have 2 bottles of Arctic Alumina thermal adhesive. But it doesn't tell me how much I should be using on each individual star, should I use just a drop? Do the stars have to sit Perfectly flat on the Heatsink or can they be a little off? Anyone with some experience with this stuff please feel free to chime in.
If I remember correctly that stuff sets really fast and it is a 2 part epoxy type adhesive.
so mix little batches till you get the feel for the dry time..

Technically it has fairly efficient heat conduction so thick(RELATIVELY speaking) or thin coat is OK..

Just remeber the idea is to just use a thin coat over most of th base.. being sure to hit the center..
Personally I used the dab in the center and "mush and a tad twist" technique.. though it is really not THE method. ;)
oh and I never clamped them... IF I ever used it a gain I'd probably build a jig for clamping .. like putting a row of evenly spaced pipe that fit over the LED and just touched the stars..so I could apply a little pressure to the plates..completely unnecessary..;)

Use the mixing wand to apply the adhesive to the top of the chip in a
thin layer. Be careful to keep the adhesive away from traces, pins, and leads.
The flatter the mating surfaces, the thinner the layer that is required.
Stock processors and/or heatsinks with normal surface irregularities or that
are slightly concave or convex will require a layer 0.004" to 0.008 thick to fill
the resultant gaps. (Equal to the thickness of 1 to 2 sheets of standard weight
paper.) Properly lapped processors and heatsinks will require a thinner layer.
Remember you will never remove those stars again.... Well maybe.. and you could always remove the LEd's from the stars and start over someday..

I eventually just used the stuff to glue Al strips together before abandoning it all for using a drill,tap, screws, and normal thermal heatsink compound (non-adhesive).. For gluing aluminum strips "heatsink plaster" was much cheaper and still drilled and tapped for security.

http://www.arcticsilver.com/pdf/appinstruct/aata/ins_aapxy.pdf

That being said.. keep in mind I'm not detail orientated soooo YMMV..

Oh don't consider your surfaces "properly lapped".........
 

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Discussion Starter · #18 ·
So I have successfully wired two led channels and just finished and tested the third which consisted of warm white and red led's and they aren't working very well, they are all running very dim or not at all. After testing and re testing it seems that the problem is the forward voltage on the red led's is 2- 2.7v and the warm whites forward voltage is 3.2 -3.7v I dont really understand why this affects the output but it certainly does.
Any ideas how to work around this? I really dont want to have to ditch the red led's if I can help it.
 

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So I have successfully wired two led channels and just finished and tested the third which consisted of warm white and red led's and they aren't working very well, they are all running very dim or not at all. After testing and re testing it seems that the problem is the forward voltage on the red led's is 2- 2.7v and the warm whites forward voltage is 3.2 -3.7v I dont really understand why this affects the output but it certainly does.
Any ideas how to work around this? I really dont want to have to ditch the red led's if I can help it.
Please explain the exact driver and string count.. One thing I always check is to see if wires were bridging the heat sink... i'll get to that in a minute..
you can check each w/ a DVOM to check for "Shorts" to heat sink..

As a matter of simplicity I always match V(f)'s but when using constant current is "should" work just fine.. Your voltage drop will just be the sum of the various V(f)'s at that current.. say 700mA

Just a reminder I guess..
Q: What's the deal with LEDs wired in series or parallel? What about "current hogging" and "thermal runaway"?
A: If your input voltage and current are acceptable, LEDs can be run in series or parallel. The issue is how well the setup will work, and how reliably. LEDs experience "Vf shift" when they heat up, with Vf dropping as temperature rises. With a constant-current (CC) source, this is no problem, as the only effects will be less light (because of the heat) and less power consumed (a lower Vf affects the V*A=W formula). Otherwise, there won't be much to worry about. With a constant-voltage (CV) source, however, the Vf shift comes into play. If Vf for a particular current goes down, but you're only keeping the VOLTAGE constant, the current at that voltage will go up. This is a problem because it will cause more heat and further Vf shift, drawing more current, leading into a feedback loop where the LED(s) eventually pop from the stress. This is what is called "thermal runaway." As you might guess, this is an issue when deciding between a series or parallel LED setup. Recall that devices in series will all draw the same current (at whatever voltage each device needs for it), while devices in parallel all see the same voltage while having potentially different current levels going through each one. If you have a CC driver running a series LED string (a "string," or "leg," is a group of devices, like LEDs, connected in series), you won't have thermal runaway problems. However, LEDs in parallel, even driven by a CC source, can experience "current hogging." As the devices are in parallel, they won't necessarily have the same current. Each string in a parallel array driven by a CV source can experience thermal runaway. If driven by a CC source, one string can still undergo thermal runaway, but another string sharing the CC source will simply get less of the total current - the current was "hogged' by the other string. If your CC source in such a setup is set to drive LEDs near their limits, then having one string bear the load intended for two or more strings can be problematic. Remember that when LEDs pop, the circuit breaks, leaving the other strings in a parallel setup with a kind of surplus of current, which leads to even more rapid thermal runaway, which will eventually leave you in the dark. This is why it's generally recommended to wire LEDs in series, as well as using a CC source if possible. If you don't have a CC source, use an adequate resistor to limit current.
http://www.tigerhawkt3.com/welcomemat/ledfaqs.htm#9
 

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Discussion Starter · #20 ·
Sorry for not giving more detail.
Im using the makers 5 channel controller with makers drivers. So I am running 14 led's per channel (48v power supply).
First thing I did was check to make sure nothing was grounding out. Then checked the individual led's with a multimeter to make sure they were ok.
 
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