DIY LEDs - The write-up

[der_wille_zur_macht]

Will this work

From the RC LED guide on heatsinks
http://www.reefcentral.com/forums/showpost...;postcount=4994

("œPower of Single LED = 3.4 Forward Voltage X 700 mA = 2.38 W, Using a 3mm plate looks about 20 cm^2 per LED converting to inches is equal to 3.1 in^2")

I would be over in sq. inches 4.5 vs. 3.1
Heat sink 12" x 9" = 108, 108 / 24 = 4.5 sq. inches per LED,

And under in Watts @ 1.085 W vs. 2.38 W
3.1 Forward Voltage X 350 mA = 1.085 W

Heatsink 12" x 9" x 1/8 plate

2- Mean Well ELN-60-48D dimmable drivers


String A = 8 Neutral-White EndorStar + 2 Blue EndorStar @ 350mA
String B = 12 Royal-Blue EndorStar @ 350mA

Arctic Silver Premium Adhesive

Soldering iron is this ok, or is there something better
Aoyue 937+ Digital Soldering Station
$53.99 @ http://www.amazon.com/gp/product/B000I30QBW/ref=oss_product

Thanks
Ken

The link you posted is broken and I'm a bit confused what you're asking about when you say "will this work."

That iron is OK - it's the one I use so I may be biased but it's soldered plenty of LEDs just fine for me. Crank up the heat. Order a different tip when you get the iron, the one it comes with is very fine and very long, which is bad for soldering jobs needing lots of oomph.

I am using it to dim 4 eln-60-48d drivers

That supply will not work. It's providing 4.8v DC. For an ELN, you want 10v DC.

anyone used this thermal grease:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=101700F00000G-ND

or got a link to some they would recommend. Need it for ~200 LEDs. Anything i should watch out for on grease?

I'm not picky about thermal paste myself but you probably don't want to try to order that particular product from digikey, as it's a non-stock item with a minimum order quantity of 220!

 

[Flazky]

T



That supply will not work. It's providing 4.8v DC. For an ELN, you want 10v DC.

Hmm im wondering where you get 4.8 DC from cause it says 8.4 on the label correct? I also wont be using full blast on my LED's as I want them to last just a tad longer, so looking to get around 800 mA per driver?

 

[PurpleMonster]

Working out the final details with Mike at RapidLED! here is the final call......

2 Dimable Drivers, and 2 Non Dim at 700ma
1 12 LED string of XPG whites (Attached to APEX)
1 8/4 of Whites(XPG)/Roya Blues(XRE) on non dimable will come on after the two others are at 100%
1 12 LED string of XRE Royal Blues (Attached to APEX)
1 12 LED String of XPG Whites on non dimable will come on once the two others are at 100%

2 Heatsinks to help me adjust the spread if i have to, each one measuring 4.25X23 each. For cooling It will depend on if i can use both heat sinks together dead center or if i have to separate them a bit. If I can run both together to create a 8.5X23 then it will be housed in acrylic with a decent sized fan at the top to suck air out. I have a few ideas for to force air through the fins. Now its a waiting game for me to get the goods.....

Thank you all very much for your input! it was all combined and a decision was made based on all the input

Thanks.

 

[Milad]

After taking a day off at work I brewed a pot of coffee, put on Pandora and went at it. Half a day later I mounted 297 LED's with optics. My hands are raw and I smell like silicon but its VERY close to being finished.

I am doing a 2:1 ratio of RB to NW in rows. Spacing is 1.5" apart with 40 degree optics. The fixture will be 12" off the surface of the 3' tank. I mounted the LED with Bond Ply and Gap Pad which are both AMAZING products. Not having to worry about drilling and tapping eases the mind

Bond Ply

A Few Optics

It has Begun!

All Mounted

The 300 Army with there shields

Hope you enjoy. When I am finished I will make sure to add a video. This will be dimmable from 40-100%.

-Dave

P.S - Kcress, I posted the parallel image on NR lighting forum. I hope you dont mind! Thanks for all your help!

whats the size of those heatsinks? is the tank viewable from both 96" sides?

 

[DFason]

30" Heatsinks. Four are 8" wide and the others are 7" wide. The tank is viewable from both sides.

-Dave

 

[der_wille_zur_macht]

Hmm im wondering where you get 4.8 DC from cause it says 8.4 on the label correct? I also wont be using full blast on my LED's as I want them to last just a tad longer, so looking to get around 800 mA per driver?

Sorry, that's my touch of dyslexia showing through. You are correct, it's 8.4v. It would likely be fine to dim ELNs. You'll loose about 30% of your resolution but that's probably not a critical thing. the internal current limit trimpot definitely has enough range to get 800mA with an 8.4v signal.

Just keep in mind that if you ever do switch to a different supply (i.e. one that actually provides a 10v signal) you'll need to re-adjust the current limit trimpot, because you will have essentially calibrated to your 8.4v signal.

Working out the final details with Mike at RapidLED! here is the final call......

2 Dimable Drivers, and 2 Non Dim at 700ma
1 12 LED string of XPG whites (Attached to APEX)
1 8/4 of Whites(XPG)/Roya Blues(XRE) on non dimable will come on after the two others are at 100%
1 12 LED string of XRE Royal Blues (Attached to APEX)
1 12 LED String of XPG Whites on non dimable will come on once the two others are at 100%

That's a VERY VERY white-oriented build - your total ratio is 32 white XP-G to 16 royal blue XR-E. Most people would probably reverse the ratio.

 

[S2minute]

Hey guys, while AT work heh, i tinkered with the math and templates and optics. One driver/led combo i came up with turned out to match exactly at that drivers limit of 42V.
So, i`m sayen to myself, sweet.....but then thinken wait because of those small variations in the Voltage of individual leds that might put me OVER the drivers 42Vmax and that`s no good. So am i right on that?? I played it safe and decided to work with a smaller build of LEDS cause at that point i had 102!!! yes 102 LEDs per section...and i would have had the biggest badest build in the world!!....Then i smacked myself back into reality.
SO, what i decided to do based on willies and Kcresses diagrams and awesome explinations, was to do 3 sections with 63 LEDS on each and build one at a time just to see. Each section will have:
1x HLG-185-36B 5.2A
7 strings of 9,1.5" between LEDS and 1.75" between rows, (6RB, 3W) each string total 31.3V which is well below 36V for the driver.
XR-E RB @700MA 3.5VF----XP-G: NW-R3,OW-R4,CW-R5 all 3.2VF@ 700MA
The reason WHY i picked 3 different Whites is this: NW 3.7-5.0 K, OW 4.3-5.3K, CW 5.0-8.0K. A nice even coverage and blend of white light.
I went further by lightly penciling in on my template, the approx. areas of the major LR formations in the existing tank,(high/low areas), and concentrated more of the white leds to the higher LR formations where most of the SPS will be. I also penciled in optic lens sizes ranging from 40 to 80 degrees based on what color led i am going to use and where that led placement was to be in the tank. I`m also going to angle the 2 end sections at about 30 degrees for a better coverage and effect. Esp. when i use willies controller to sim sunrise/set, lunar cycles and weather.
So, i`ll do one section, screw it down and throw it up there to see how it will look and if i like it, i`ll tweek it to balance the LEDS VF in the strings and get rdy to build section 2...then section 3. Sound good?

 

[der_wille_zur_macht]

Hey guys, while AT work heh, i tinkered with the math and templates and optics. One driver/led combo i came up with turned out to match exactly at that drivers limit of 42V.
So, i`m sayen to myself, sweet.....but then thinken wait because of those small variations in the Voltage of individual leds that might put me OVER the drivers 42Vmax and that`s no good. So am i right on that??

You are more or less correct. You don't want to go over the driver's max voltage, otherwise it won't be correctly regulating the LEDs in a constant current mode. Check the driver's datasheet carefully, as most of them give a "constant current range" which is a range of voltages over which it can operate in a constant current mode. I'd suggest staying at least 10% below the endpoints of the specified range to provide room for variation in LED Vf.

1x HLG-185-36B 5.2A
7 strings of 9,1.5" between LEDS and 1.75" between rows, (6RB, 3W) each string total 31.3V which is well below 36V for the driver.
XR-E RB @700MA 3.5VF----XP-G: NW-R3,OW-R4,CW-R5 all 3.2VF@ 700MA
The reason WHY i picked 3 different Whites is this: NW 3.7-5.0 K, OW 4.3-5.3K, CW 5.0-8.0K. A nice even coverage and blend of white light.

Sounds reasonable, but a few comments. Firstly, if you do nothing but "mixed" strings like that, you won't be able to dim colors separately to modify the overall tint of the light. This shouldn't be a show stopper but many people like being able to dim colors separately.

Secondly, particularly about this line:

The reason WHY i picked 3 different Whites is this: NW 3.7-5.0 K, OW 4.3-5.3K, CW 5.0-8.0K. A nice even coverage and blend of white light.

It's very important to understand that the kelvin color specification you are quoting is for an ENTIRE RANGE for a particular model and color of LED. If you go to a retailer and buy a single LED, it WILL NOT cover that whole range of colors! It will provide light at one single point within that range. The color bin for a particular LED will tell you where within that range you land. For instance, the spec for cool white shows 5 - 8k, but if you end up with an LED in the 0A color bin, you'll have a kelvin color around 8000k, but if you have an LED in the 2A bin, it'll be more like 5800k.

This isn't a big deal but I want to make sure you understand it, so you don't assume that buying a cool white XP-G LED gives you that WHOLE range of colors.

I also penciled in optic lens sizes ranging from 40 to 80 degrees based on what color led i am going to use and where that led placement was to be in the tank.

This is a noble process but I would strongly encourage experimentation before committing. Especially if you are blending different optic widths on different colors of LEDs - it's very easy to get weird and undesirable effects, like color separation and multiple shadows.

 

[kcress]

That's multiple shadows visible to you - the viewer - because the different color shadows could possibly be seen. (But then possibly not too..)

S2; from your discription I can't make out if you're planning to have different mixes in your strings. I'll just remind you, you can't!

Now on the voltage limit. Those higher end drivers list a higher voltage than the model value. Like 50~30V for a 42V 'model'. That means that likely they can can run string voltages right up to the model value and always be able to drive at that - especially if you don't actually run the driver at its maximum current.

 

[PurpleMonster]

That's a VERY VERY white-oriented build - your total ratio is 32 white XP-G to 16 royal blue XR-E. Most people would probably reverse the ratio.

Goes to show how tired i was last night Sorry lol....

28 XRE royal Blues to 20 XPG whites Dont know what i was doing when i wrote that up.... i need to figure out how the heck im going to lay out the LED's so that i dont have any spot lighting.

Not sure if i want to bolt both 4.25X23 heatsinks together or if i want to run them separated a few inches so that i can get more coverage.


Thanks

 

[TheFishMan65]

IMHO, separate you will also get better cooling, because of the airflow between modules.

 

[PurpleMonster]

Thanks fish, I didnt think of that so much and i will probably do that. I am picking up some L aluminum stock to make the frame for the heatsinks to sit on. I will make sure i get enough to be able make the lights adjustable from front to back.

Thanks.

 

[sahin]

Guys, have a few more questions for you: I want to mix in 4 Blues with 8 Royal Blues (to improve the spectrum a little), is this ok? They are Cree XRE LED's. I am going to use a Meanwell LPC35-700. Or should I wire them in at the end of the circuit going back to the black wire on the Meanwell?

Does it even matter? Many thanks.

 

[TheFishMan65]

You can mix LEDs on a string with the following limits
- it may not allow dimming one color to get a desired color
- you can not exceed the Vf of the driver
- if you are using a parallel configuration each string must have the same configuration of LEDs.
maybe some others but I think that sums it up.

 

[der_wille_zur_macht]

Only thing I would add is that current in the mixed string must be below the max rating on the lowest rated LED.

 

[S2minute]

That's multiple shadows visible to you - the viewer - because the different color shadows could possibly be seen. (But then possibly not too..)

S2; from your discription I can't make out if you're planning to have different mixes in your strings. I'll just remind you, you can't!

Now on the voltage limit. Those higher end drivers list a higher voltage than the model value. Like 50~30V for a 42V 'model'. That means that likely they can can run string voltages right up to the model value and always be able to drive at that - especially if you don't actually run the driver at its maximum current.

wow, that`s a bummer, i thought i could as long as the counts on each string was exactly the same and if each color group had the same VF.
Like ledA---ledA---ledA---ledB---ledB or any order, as long as the all of ledA was the same Vf and all of ledB Vf was the same on each string.
The way the strings were to be set up was like this:
RB XR-E will be driven @ 700MA and that`s 3.5Vf
White XP-G, even if they are 3 different types of white @700MA they are all 3.2Vf
So the strings: Ex: 1) RB,RB,CW,RB,RB,NW,RB,RB,OW (6 RB, 3 White)
2) RB,OW,RB,NW,RB,RB,RB,CW,RB ect. for 7 strings.
Each string would have the exact same count but, in different order on parallel strings. So now what is wrong?? I thought i had it finally

 

[widmer]

There are small individual differences from one actual LED to the next, and they have crazy-steep current vs voltage curves. So if you wire a bunch up, even if they're the same model LED it's likely that the two strings will have a different vf which can profoundly impact how much current is running through it.

 

[der_wille_zur_macht]

You can put any LEDs in any order you want on any string. The rule is this: The total Vf of each parallel string on the same driver MUST BE THE SAME.

So, assuming LED A drops 3.5v and LED B drops 3.2v (the blues and whites you are using) you could have the following strings on the same driver:
1) A, B, A, B
2) A, A, B, B
3) B, B, A, A

You CAN NOT have these three strings on the same driver with those LEDs:
1) A, A, A, A
2) B, B, B, B
3) A, A, B, B

If I am understanding you correctly, you want to make strings like:
1) RB,RB,CW,RB,RB,NW,RB,RB,OW
2) RB,OW,RB,NW,RB,RB,RB,CW,RB

Your two strings have the same counts of each LED so they'll have equal Vfs, so you will be perfectly fine. Keep in mind though that you still MUST test your LEDs/strings to ensure that they are all actually in spec, as Vf specifications are weak at best, and even small deviations can result in large changes in current.

 

[der_wille_zur_macht]

Double post...

 

[TheFishMan65]

The order can vary. The mix can not.

Now that is not completely true if you had 2 LEDs that had 1/2 the Vf of another then you could do a 2 to one swap. BUT you better be SURE that that rule is true at all currents even as the LEDs age. IMHO not worth the risk.

[EDIT]
"and even small deviations can result in large changes in current. " +10