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Unread 09/24/2010, 06:31 PM   #1
csarkar001
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Yet Another DIY LED Build Thread

already discussed to death? perhaps. but here is what is different about the fixture i am building:

1> it is for a 6 ft fish-only tank
2> it uses some non-traditional LED colors
3> it uses some non-traditional wiring schemes
4> it uses a reefkeeper lite (RKL) advanced light controller (ALC) to control the LEDs
5> it will feature a controller bypass mode for instant on

interested? the going promises to be slow but most enjoyable journeys are ...

as i await the arrival of my Cree LEDs from Cutter in Australia (yes, from north carolina to connecticut by way of the land down under), lets start by talking about some of the challenges.


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Unread 09/24/2010, 06:39 PM   #2
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i did not know the RKL would work a the light module - that's good to know as I was thinking about going the same way


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Unread 09/24/2010, 06:53 PM   #3
csarkar001
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Question Looking for Suggestions on Color Mix

hopefully, my decision to use CREE will not reignite the CREE debate on this forum. my personal choice for going with them is loosely related to my work. otherwise, i dont think the vendor choice is that important.

the standard design for a DIY LED project with 48 LEDs would "normally" be 24 CREE cool whites and 24 CREE royal blues. (apparently already a tradition)

i was all set to order that combination until i came across this disturbing thread (started by a fellow discus keeper, no less).

so instead of the usual 50/50 white/royal blue mix, i have ordered the following:

10 CREE XPG cool whites
10 CREE XPG neutral whites (as suggested by the emperor thread mentioned earlier)
22 CREE XRE royal blues
10 CREE XRE blue (more like a sky blue, i have been told by DWZM)

from this batch of 52 LEDS, i hope to pick 48 that offer some color balance. one problem i anticipate even before i begin is that the XPG's are so much brighter than my blues and royal blues, they may drown them out. so i may have to play with the ratio. does anyone have any experience/suggestions with this?

i will also probably put most of the whites on a separate dimmer control so that i can adjust the color ratios after the project goes live. but it would be good to get close to the optimal ratio at the build stage. but is optimal entirely subjective?

i do want a lot of that unnatural blue (actinic-like) tinge that the royal blues offer but also want a reasonable amount of brightness for my 6 ft tank as well. since i do not have corals, i do not care about PAR values - no optics planned for this project.

i'm taking suggestions on the color mix while my soldering iron gets hot.

also, will 48 LEDs be enough to light a 72" x 20" x 30" fish-only tank?


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Unread 09/24/2010, 06:54 PM   #4
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Quote:
Originally Posted by psteeleb View Post
i did not know the RKL would work a the light module - that's good to know as I was thinking about going the same way
the RKL needs "a little help" to drive my Mean Well LED drivers. i'll explain soon in this thread. i'm waiting for the DA guys to rubber stamp my design before posting it here.


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Unread 09/24/2010, 07:03 PM   #5
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thanks - i'll tag along for the ride


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Unread 09/24/2010, 07:36 PM   #6
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Proposed LED and Dimmer Layouts

My project will use 48 LEDs set up in four pods (groups) of 12 LEDs each. Each pod of LEDs will be mounted on a predrilled heatsink like this:



i am not creative (or daring) enough to try to shine different colors of light into different parts of my tank so each pod will have the following LED mix:

2 or 3 cool whites
2 neutral whites
5 or 6 royal blues
2 blues

but even though the pods will be homogenous with respect to color, i plan to dedicate my three Mean Well LED drivers as follows: one will control just the white LEDs. One will control only the blues. the last one will control whatever is left over.

finally, i plan to secure all the pods and the meanwell drivers together on to a rectangular frame using angle aluminum stock i purchased from home depot. my tank and canopy are acrylic. my plan is to glue 1" acrylic cubes on to my canopy and to drill screws through the aluminum stock into the acrylic cubes to mount the entire fixture.

please let me know if you have any thoughts on whether this LED layout scheme makes sense and if you think i will end up needing a fourth MW driver. is it ok to share the driver across multiple pods/heatsinks?


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Unread 09/24/2010, 09:17 PM   #7
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Some Challenges to Using a ReefKeeper to Control LEDs

As much as i like my Digital Aquatics RKL controllers (i own three), when it comes to their new Advanced Lighting Controller (ALC), this module is a bit of a camel - a horse designed by committee. their challenge has been to try to build one module that can control lots of different lighting fixtures - most of them commercially made. it looks like they have only partially succeeded.

the ALC has two outgoing analog dimming channels 0-10V DC. since my Mean Well ELN-60-48D dimmable drivers take 0-10V DC on their input lines, all would seem to be well ...

... however (and here is where the trouble starts), the meanwells require several milliamps of current on these input lines to function properly while the ALC supplies only about one milliamp on each channel.

this has been discussed on the DA-ALC forum with posters mentioning that the ALC can drive a single Mean Well but driving multiple drivers becomes a real struggle. (i worry even driving one Mean Well could possibly damage the ALC longer term given its current feed limitations).

the other problem with the ALC is that there is no way to turn on the lights to full power instantly (for maintenance or whatever other reason you might have for wanting them on immediately). even if you press the button sequence to turn on the LEDs, they still go through their programmed ramp time before getting to full power. it is possible that the folks at DA will fix this issue in a future software release of the ALC. but they might not.

i think it may be possible with the addition of a (hopefully) simple circuit to fix both of these issues. i have posted this potential solution on the ALC forum and am waiting for the DA guys to look it over and give me their go-ahead before i build it. but i'm going to post it here also since there is a lot of expertise on this forum which may be helpful in resolving these issues.

here is my idea:



this combination voltage follower (current buffer) circuit and resistor combination should do the trick. the op amp provides the additional current the Mean Well drivers need. meanwhile, the combination of the toggle switch and the resistors offer an option to bypass the ALC and turn the LEDs on to full power at the press of a switch. i'll post more on this idea after i get a response from the DA team. i have not worked with op amps since graduate school. so this is going to be "fun."


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Unread 09/25/2010, 10:11 AM   #8
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Question How to Divide ALC Dimming Ports?

The RKL ALC has two 0-10V dimming ports. my plan is to use one to control the white LEDs and the other to control blues. my hunch is that when the lights are on, i will end up setting the blue port to be near full power most of the time (except maybe at night for a moonlight effect), and i will end up varying the white LEDs over the course of the day. but since both ports are under computer control, i hope to have some room to err, should my hunch prove wrong.

what do most of you folks with 50/50 white/blue ususually do?


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Unread 09/25/2010, 10:39 AM   #9
chuckstyl5
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You can connect the ALC right to the Meanwells -- Thats how I had mine setup --- I had a total of 6 meanwells 3 on DIMA (blues) and 3 on DIMB (white) and everything worked great


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Unread 09/25/2010, 07:52 PM   #10
csarkar001
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Quote:
Originally Posted by chuckstyl5 View Post
You can connect the ALC right to the Meanwells -- Thats how I had mine setup --- I had a total of 6 meanwells 3 on DIMA (blues) and 3 on DIMB (white) and everything worked great
if you are right, i can avoid this extra circuitry. however, several posters on the DA-ALC boards are reporting when you hook up multiple meanwells to the DIMA and DIMB ports, the ports do not reach full voltage when programmed to do so. have you actually used a volt meter to see if its getting to 10V when you set it to 10V?

i'll run an experiment and post the results here just to verify once my LEDs arrive and i get started. but the number of complaints on the DA message board on this topic are many.



Last edited by csarkar001; 09/25/2010 at 08:01 PM.
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Unread 09/26/2010, 05:55 AM   #11
der_wille_zur_macht
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Not going ALL the way to 10v may be a theoretical/design problem, but in practice it's not an issue - as long as your max is somewhere near 10v (i.e. 9.2v, 8.9v, whatever), the only real "problem" will be that you'll lose a few percent of resolution in the dimming range. In fact, some people are setting up manual dimming controls with 9v wall warts, so they're in the same boat. The only real gotcha is that you want to be sure you're adjusting the internal current limit trimpot when you're running at your "real world" max voltage.

That said, I appreciate the design of your circuit, and it's so simple that I'd probably do it anyways if I were in your shoes, since dimming resolution is a precious commodity with ELN drivers (thanks to that big cutoff down low).

I also applaud your decision to experiment with different colored LEDs. Be sure to let us know what you think of your final arrangement! The one caution I would have is that on a lower-density (i.e. count per unit of area) build, it's tough to mix LOTS of colors of LEDs and have an even coverage of each color. So if you're running a small experimental panel to test color mixes, make sure you watch for separation between the colors, colored shadows, etc. before applying a certain ratio to the whole fixture.


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Unread 09/27/2010, 11:30 AM   #12
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one of the other posters on the DA-ALC forum has just tested out a slight variation on this proposed wiring diagram.

he has replaced my resister bridge with a trim pot and also added an LED to indicate when the system is in manual mode. the pot allows the user to control the level of the LEDs fully when the system is in manual mode. these are both good modifications and so i will probably adopt them.

i will verify this but he is also reporting that the inputs to the MeanWell 48D drivers each consume 24mA! that is a big number.

i'll post an updated wiring diagram down the road when i build this ...

meanwhile, still waiting for parts to arrive in the mail.


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Unread 09/27/2010, 11:35 AM   #13
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Quote:
Originally Posted by der_wille_zur_macht View Post
That said, I appreciate the design of your circuit, and it's so simple that I'd probably do it anyways if I were in your shoes, since dimming resolution is a precious commodity with ELN drivers (thanks to that big cutoff down low).
it appears that linearity of dimming is not so good without this type of circuit. at least that is what a third party on the ALC message board is reporting to me. i will, of course, eventually see for myself.


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Unread 09/27/2010, 11:37 AM   #14
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Linearity and resolution sucks on these drivers no matter what, IME.


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Unread 09/27/2010, 01:03 PM   #15
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I use the aquasurf as a dimmer for my DIY LEDS. The aquasurf is powered by a 9V wallwart. The current it draws at 100% is only 2mA. I have one port controlling 3 MW. I don't know about 24mA that was quoted. The linearity really does suck with the MW. At 50%, the current is like 700mA instead of 500mA with a 1A max.


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Unread 09/27/2010, 01:32 PM   #16
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Quote:
Originally Posted by swannking View Post
I use the aquasurf as a dimmer for my DIY LEDS. The aquasurf is powered by a 9V wallwart. The current it draws at 100% is only 2mA. I have one port controlling 3 MW. I don't know about 24mA that was quoted. The linearity really does suck with the MW. At 50%, the current is like 700mA instead of 500mA with a 1A max.
a lot of mixed data on current consumption for the MeanWells. but everyone seems to agree that their linearity sucks. i will post my results in a couple of weeks once i have them ...


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Unread 09/28/2010, 06:32 PM   #17
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Considering some alternate wiring strategies

i'm guessing most DIY LED projects get wired in series like shown in the top half of this diagram:



but my first thought was to wire my LEDs like shown on the bottom half of the diagram. the idea is if any one LED fails, all the others still have a current path. (has anyone built an LED project like this?)

the problem with this scheme is that when one LED fails, the other LED in the pair has to absorb the entire current load. if the LEDs have a max current of 1000 mA, i wont be able to drive them by more than 500 mA in order to avoid any overdrive problems. this seems like too much of a compromise.

i'm therefore considering this wiring scheme:



using this parallel strategy, i hope to get my project completed possibly with only two meanwell drivers (one for white and one for blue). i still have to calculate the max number of LEDs i can drive using this strategy. if it turns out i cannot reduce the number of drivers using this strategy, i'll just go back to the simple series wiring.


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Unread 09/29/2010, 07:08 PM   #18
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Neutral White versus Cool White: What Ratio to Use

My LEDs arrived from Cutter today. i spent most of the evening staring at LEDs so of course i'm nearly blind now.

regardless, i've already begun to arrive at some early conclusions:

not knowing any better, i ordered a 1:1 ratio of cool white to neutral white but now i realize that i should have gone with a 2:1 or even 3:1 ratio. otherwise, i think there will be too much yellow light in the final product (contributed by the neutral whites).

similarly with the royal blue versus blue, i think a 2:1 ratio is preferable to the 1;1 ratio i have ordered given that i want that actinic look.

i'm tempted at this stage to cut back my design to 36 LEDs (instead of 48) so i can get the proper color ratios that i want without having to order more LEDs and to use the leftovers on my next LED project.


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Unread 09/30/2010, 01:26 AM   #19
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Your last wiring scheme could work.

The problem is the actual Vfs of the individual LEDs. You could have a few in one string with low Vfs and end up with it hogging the current.

I'd probably add a resistor to each string to help balance the strings. That would also allow you to measure both string's currents without disturbing them. That will show you if one is hogging because you likely won't be able to see it with your eyes.


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Unread 09/30/2010, 05:24 AM   #20
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Quote:
Originally Posted by kcress View Post
Your last wiring scheme could work.

The problem is the actual Vfs of the individual LEDs. You could have a few in one string with low Vfs and end up with it hogging the current.

I'd probably add a resistor to each string to help balance the strings. That would also allow you to measure both string's currents without disturbing them. That will show you if one is hogging because you likely won't be able to see it with your eyes.
thanks for the suggestions. i'm also worried if the LEDs may fail before the fuse.


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Unread 09/30/2010, 01:46 PM   #21
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thanks for the suggestions. i'm also worried if the LEDs may fail before the fuse.
That is the question.. The problem is if one LED shorts in a string. Now that string's current goes up. Does it go up enough to blow the fuse in a timely manner? Hard to say. You might have a second LED short and now the fuse will blow. Cost - one more dead LED than the one that failed out of turn.

Now the fuse blows on the faulty string. The entire current tries to run thru the adjacent string. Its fuse blows promptly if sized right.

Probably the safest parallel scheme is to run three strings with the current set to run two at their maximum rated current. Then when one string fails the other two run at their maximum, not over their maximum. This gives you the opportunity to notice a large lighting discrepancy in your display. You would still want fuses in each string to prevent the mythical zipper effect of all LEDs in a string frying.

Alternatively, assume some LED in a distressed string opening as a fuse. Failing open is more likely than failing shorted anyway. Run all your strings in parallel. Keep spares. Something goes wrong you may end up with one or two blown LEDs in all your strings. Is that really a big problem for a DIYer? You don't have to take it all down and ship it somewhere and have them hose you for repairs while they take three weeks to turn it around.

I would likely run the three-strings-method above. I would add a permanent current measuring resistor to each string. 1 ohm, 2 or more watts. Run the fixture. Using a voltmeter check the voltage drop on the resistors. Do the math. Calculate the current on all the strings. Are they all within 10%? Yes? Run with it.

If they aren't within 10% then you need to fix it. Again, using your voltmeter, on its lowest scale that does the job, measure the voltage drop Vf caused by each LED. Write them down. Do this on all the strings.

Find the lowest Vf in the string with the highest current. Swap it with the LED having the highest Vf in the string with the lowest current.

Now recheck the three string currents via the voltage across the current resistors. They will be much closer now. Close enough? If not, just continue the process until your three strings match within 10% or whatever you deem reasonable.

If you have mixed colors in the strings you can restrict the swaps to a specific color without any issue.


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Unread 10/03/2010, 08:10 PM   #22
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building a frame for mounting the LEDs

all the parts have now arrived. i started by building a frame for the entire project using aluminum stock i bought from home depot. i have downsized the project to 36 LEDs down from an orginal plan of 48 LEDs. that means three pods with 12 LEDs each. i'm going to use this LED build for my 125 gal tank and will build a separate, larger project for my 200 at a later date.

this is a picture of one of the heatsinks mounted on the frame:



and here is a picture of the entire frame with all three heatsinks mounted:



the pods are about 10" apart from one another. is this going to leave dead spots in my 5' tank? the overall frame is 60" long.



Last edited by csarkar001; 10/03/2010 at 08:27 PM.
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Unread 10/03/2010, 08:17 PM   #23
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Question looking for feedback on final LED build plan

after playing with the blue, royal blue, cool white, and neutral white LEDs, i have tentatively decided on the following for my 36 LED build:

9 cool white
3 neutral white
16 royal blue
8 blue
-----------------
36 total

i decided on a ratio of 3:1 for cool white to neutral white because the neutral whites had much more yellow in them than i had expected. i do not want so much yellow in the final product. similarly, the royal blues had more of the deep blue i was looking for versus the regular blues.

overall, i also decided to have a 2:1 ratio of blue to white LEDs because i am using XP-G whites versus XP-E blues (all CREE products). because the XP-Gs are a lot brighter, i went with a larger number of blues so that they do not get drowned out by the whites.

would love to hear some opinions on this final mix before i start wiring next few days. any thoughts?


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Unread 10/04/2010, 07:49 AM   #24
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That strikes me as a reasonable mix. If it looks good to you, that's all that really matters! It's definitely within the realm of what you could expect to get "good" results from.


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Unread 10/04/2010, 08:34 AM   #25
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That strikes me as a reasonable mix. If it looks good to you, that's all that really matters! It's definitely within the realm of what you could expect to get "good" results from.
thanks. i'm frankly more worried now about coverage and unevenness throughout my tank. hopefully 36 LEDs will be enough!


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