Diy led questions

[Cole Harlow]

If i had a twoft wide tank and put a 9 inch wide heatsink on it with 36 leds right in the middle would the leds be abl to cover the 6 inch space on each side of the heatsink

[Learning_The_Hard_Way]

Depends on how high you have it mounted above the tanka nd the angle of lens you put on the LED.

[DarinSchmidt]

funny that you should ask that. I have a 27" wide tank with 8.5" wide heatsing. properly spaced out LEDs and they seem to do really well with lighting the surrounding area. My tank is also 24" deep and my lights sit above the water about 3-4" and have 80 degree optics on it. I would recommend raising it a little higher though, maybe 6-10 so there is even better spread.

[Cole Harlow]

How big is your tank and how many leds do you have on it total. What kind af corals are you keeping under it

[DarinSchmidt]

My tank is about 300gal. 128 leds. I have sorties, Lps, and sps

[Cole Harlow]

do leds have the same wattage no matter what percent there at

[Wall_Tank]

No.

Watts = Voltage x Current

So an LED that uses 3.3volts at 1amp   at maximum power would use 3.3 watts

When you dim an LED, the current drops, the voltage for the most part stays the same

So an LED at 50% power would be

3.3 volts x 0.5 amps = 1.6 watts.

[DarinSchmidt]

Correct wall. But in a system like the one I made, you drop the voltage of the led to dim it because the voltage is directly related to how many mA it will consume.

[kattz]

If you're using a Meanwell ELN-series driver, the LED brightness is controlled by output current, not voltage.  External voltage is referenced to drive the unit current output, not voltage output.

Kev

[Wall_Tank]

Correct wall. But in a system like the one I made, you drop the voltage of the led to dim it because the voltage is directly related to how many mA it will consume.

LED's are not a resistive load.  Voltage and Current are not related like a light bulb.   Very slight changes in voltage can produce drastic changes in current draw.   Forward voltage also changes as a function of heat.

You are using a voltage regulated power supply, with a resistor in the line to limit the maximum current draw.   It will work, but is not the preferred way to power LED's.   And if you want to do dark to full dimming, you'll need current control.

Current regulated power supplies is the preferred method of driving LED's

[DarinSchmidt]

If you look at an LED data sheet, it specifically shows that if you apply a certain voltage, it will draw a certain amount of mA. Using a voltage adjustable power supply works just as well as the expensive constant current drivers. The only difference is that with an adjustable voltage power supply, the can vary +-5% depending on the hardware used. Mine varies about 2%. The Voltage and Amps is directly related to how many lumens are pumped out.

[Wall_Tank]

Okay, so some good debate between two non-electrical engineers.   Will see when Wes decides to chime in.   But here is the curve from the Cree XR-E



Your talking in theory, I'm talking in practical control.   Anyone who deals with system dynamics, knows that you want to operate on any flat portion of a response curve.   If your system is operating above 3 volts.  You are going to see much more current swings.   Unless your operating against your current limiting resistors in your system.   Light output is a function of current not voltage.    So if you want consistent light output, then you need to control current.

[Cole Harlow]

Just wondering but what percant do most of you run your leds at
Thanks for the help

[DarinSchmidt]

Okay, so some good debate between two non-electrical engineers.   Will see when Wes decides to chime in.   But here is the curve from the Cree XR-E

Your talking in theory, I'm talking in practical control.   Anyone who deals with system dynamics, knows that you want to operate on any flat portion of a response curve.   If your system is operating above 3 volts.  You are going to see much more current swings.   Unless your operating against your current limiting resistors in your system.   Light output is a function of current not voltage.    So if you want consistent light output, then you need to control current.

Well then explain how my system works if it's "theory". You cannot fully dim the LEDs with the way i do it as there wouldnt be enough for the LED to actually function if trying to dim them to dark. But like i was saying with my system, i dont dim my lights. It turns on at 750mA and remains that all day. If i want to bing them down to 350mA or bring them up to 1000mA i can just increase it's voltage. Using a constant current system like a meanwell will allow you to dim them all the way down to dark by controlling the current that goes through them. But if this isnt the option you are trying to achieve (like in mine) then this doesnt matter.

But comparing a CC unit to just a PSU with a fuse unit is in a way comparing apples to oranges. I chose the PSU way because for 128 LEDs, i saved a lot of money by not buying a CC device to run every 8 LEDs.

But also like you see in the diagram, increasing the voltage of the LED above its operational voltage does increase its current. But you must stay within 3-3.7vf for it to operate properly.
meanwell $29

from what i read, people run only 12 LEDs off these.

48v psu $48

I could run 105 off of one PSU and still have enough power for fans. BUT you should only run a PSU under 90% of its potential. So i use 2 PSU's instead of 11 meanwells. $96 vs $319.

If i was to do dimming to dark i can add a PWM which can take care of that.

[DarinSchmidt]

mine are running at 700mA if thats what you are asking.

[Wall_Tank]

We can agree to disagree on this.   All I'm saying is that you have more control with a CC power supply.   Dimming to near dark is actually one of the best affects that we get with LED technology.

If your doing just normal on/off control, there are much cheaper Meanwell CC power supplies   LPC-35-700 is only $18.   

[cyberwollf]

Im a little confused.. Darin, are you running a resistor inline or just relying on hitting the voltage correctly with no resistor???

[DarinSchmidt]

There is no need for a resistor since it has a built in POT. If the voltage gets out of hand by some freak incident the fuse will blow. So if it hits 1A then it blows. Which by having it running at 700mA, it would have to increase about 5V on my system to have it achieve such current.

Even at $18 pet controller, that's 200 bucks vs 96 for the same function. Having LEDs and being able to control them is one part of why they are a much better alternative. But using a psu system doesn't prevent you from having control. You just have to make a own for it. A meanwell is a complete package but for about 2-3x the price.

[DarinSchmidt]

Have to make a pwm for it*

[cyberwollf]

So by POT, you mean YES it has a resistor   With constant voltage from your PSU and the POT set at a constant resistance, you have constant current.  Unless you have some forward bias changes with temp. 

Sounds like a fine setup to me.  Just make sure your fuse is a fast blow fuse.

[DarinSchmidt]

Yeah. Its a fast blow. And I was just saying that I didn't install one inline since one was built is so technically yes there is one lol.

[Cole Harlow]

Is it ok to have cree xp-e and cree xp-g r5 leds two inches apart id have 72 leds on 34 inch by 8.5 inch heatseink with three 120 mm by 25 mm fans

[DarinSchmidt]

Yeah. 2" from what I have seen seems to be the standard. I have seen some at 3". The spread of the leds aslso depends on the type of optics you use and the depth of the tank. If you aren't going with optics an have a standard depth tank you might be able to get away with 3" and use less leds to save some money.

[Cole Harlow]

So im going to have two heatsinks and im trying to decide if i should do 48 per heatsink or 72 per heatsink the leds willmbe xp crees

[DarinSchmidt]

what size tank do you have?

[DarinSchmidt]

and each heatsink is going to be 34" long or combined?

[Learning_The_Hard_Way]

I have XPG and XRE mixed and they are 2.5 apart and it worked out well.  I have 65 deg optics.  The bigger the heat sink the more surface area to dispurse the heat.  I could not belive the difference a fan made in the cooling as I was considering not having one in the beggining get a good one that is low noise.

[DarinSchmidt]

Likewise hardway. I made a little test unit runing at 350mA a while back (both units in the pic below were test units), it got warm, but nothing to be concerned with, but when ramped up to around 700mA, they got really hot. Wouldnt burn you, but enough to make me concerned about the life of the LEDs.



here is an equation that i made to help easily get you in the ballpark of what you "should" have as far as lighting so that you have a good even spread, but of course optics and distance above water surface isn't factored into this yet.

FO tanks dont require as much lighting.

-------------------------------------------------------------------------
W= (total width) - (including exterior edge measurement)
L= length of tank - (including exterior edge measurement)

(((L-8)/2).6)=a = # of columns
(W-4)/2=b = # of rows
NOTE: round a and b up to the nearest unit
a*b= # of LEDs
a=rows
b=columns
--------------------------------------------------------------------------

so for example, if you have a 55g tank, 48x13:

x= distance you want between each LED
x in this case is 2
(((48-8)/x).6)= 12
(13-4)/x=4.5 = 5

the above equation requires 2 heatsinks placed evently between the braces of the tank

12*4.5=54 median
12*4=48 min
12*5=60 max


then from there you can figure out how you want to place the LEDs.

Just remember, this is a ballpark figure. I had done some testing with a couple tanks and this seems to work rather well for me.

[Cole Harlow]

I have a 210 gallon tank

[DarinSchmidt]

-------------------------------------------------------------------------
W= (total width) - (including exterior edge measurement)
L= length of tank - (including exterior edge measurement)

(((L-8)/2).6)=a = # of columns
(W-4)/2=b = # of rows
NOTE: round a and b up to the nearest unit
a*b= # of LEDs
a=rows
b=columns
--------------------------------------------------------------------------

so for example, if you have a 55g tank, 48x13:

x= distance you want between each LED
x in this case is 2 incorrect, copied this from an old thread i was working this out on, it's supposed to always be 2

(((48-8)/2).6)= 12
(13-4)/2=4.5 = 5

I believe your tank is 74x24?

if so then its 20 leds per row, 10 per column. Thats MAX. for best LED spread 1" above tank surface, so you can go lower than this if you want. 200 LEDs, min would be 120 LEDs min at 1" above tank surface. I have to still fine tune that equation as it's only partial. But, doing 7x LEDs will be fine with some optics and if lifted high enough IF spread is something you are concerned with, otherwise you will just see where the light beam focal points start to diminish which to some isnt that big of a deal since its near the edge of the tank.

I'm just going to take a wild guess that if you can get them 4-6" above water level, you shouldnt have any spread issues. I have done the same with mine, 128 LEDs over my 300 (96x27" tank). My LEDs are also 2.5" apart. But i do have a little "fade" near the front of my tank because i dont have them lifted high enough.

[DarinSchmidt]

i'll get back to you on this once i get home. I'll draw a diagram and redo my equation including the height from the sandbed to the leds.

[Cole Harlow]

My tank is 84 inchs by 24 inches

[DarinSchmidt]

ok, just to keep things basic.

you have a 34x8.5 heatsink. palce them 2" on center thats 16x4=64 leds. any more than that per heatsink and you will be reducing your LEDs a lot to not burn your corals.

[Wall_Tank]

To plan or expect 100% even light levels over the entire 72x24 foot print is bit unrealistc.  And 1" off of water is not anything to even recommend.    12" above the water surface at a minimum.   There is no reason to mount LED's low.   200 3 watt LEDs is quite a bit too many.

Is this a standard plastic framed 210?  If you have the plastic braces across the top, you need to avoid putting light directly over top, otherwise you will get nasty shadows.

[DarinSchmidt]

To plan or expect 100% even light levels over the entire 72x24 foot print is bit unrealistc.  And 1" off of water is not anything to even recommend.    12" above the water surface at a minimum.   There is no reason to mount LED's low.   200 3 watt LEDs is quite a bit too many.

Is this a standard plastic framed 210?  If you have the plastic braces across the top, you need to avoid putting light directly over top, otherwise you will get nasty shadows.

I wasn't recommending 1". I stated mine were higher. Most tank lights sit 1-6" above the water. Unless you have a canopy or a hanging unit. Have you done any tests with the 3w leds? I'd like to hear what you have to share.

[kattz]

While you're at it, use three 18" heatsinks; put your LED's at least 12" above the water - mine are 15" from splashguard to water's surface.

[Cole Harlow]

While you're at it, use three 18" heatsinks; put your LED's at least 12" above the water - mine are 15" from splashguard to water's surface.

i couldnt use 3 heatsink without one janging rightt over the glass brace in the middle of the tank

[DarinSchmidt]

If its glass o wouldn't worry about it. I do agree with using 3 HeatsinkUSA though

[Cole Harlow]

To plan or expect 100% even light levels over the entire 72x24 foot print is bit unrealistc.  And 1" off of water is not anything to even recommend.    12" above the water surface at a minimum.   There is no reason to mount LED's low.   200 3 watt LEDs is quite a bit too many.

Is this a standard plastic framed 210?  If you have the plastic braces across the top, you need to avoid putting light directly over top, otherwise you will get nasty shadows.

Its got a plastic frame but a glass  brace its not a standerd 210 its 84 by 24 by 24inches

[DarinSchmidt]

you plan on using optics correct?

[Cole Harlow]

While you're at it, use three 18" heatsinks; put your LED's at least 12" above the water - mine are 15" from splashguard to water's surface.

I was thinking about this and was wondering if i could do 3 heatsinks each with 36 leds plus the reds and plain blues to bring out the corals collars. Im probly going to use 60 degree optics rapid led has nothing bigger for xp. If i used the idea above approximattly how many nle /red leds should i have per heatsink, i also want to make sure that the lig would make it throught the glass brace in the center of the tank

[DarinSchmidt]

if you did your idea with the 34" heatsinks to avoid passing through the center brace it would look like this to scale:



its not a bad idea to do it this way though.

36" (including the 12" height above water line with 60 degree optics) gives you a 62" diameter focal point. Which is more than enough at sandbed level.
at 30" above sandbed it gives you 52" diameter focal point.

this model uses 136 LEDs

[Learning_The_Hard_Way]

Cole call Mike at Rapid LED and he sometimes can let you know if they have any coming or on the way.  I got some greater than 60 by asking.

[Wall_Tank]

Its got a plastic frame but a glass  brace its not a standerd 210 its 84 by 24 by 24inches

I run 35 3 watt XR-E's per fixture...  this is a std 90 gallon.   Maintain mostly SPS, and a few LPS in the darker corners.

The glass brace is probably not a problem, but I would avoid it.    Your going to need different intensities in your tank.  Not everything likes super bright.   So design in some darker areas and put the appropriate corals there.

I'm not sure I remember what you plan to keep in the tank?   How bright do you want it?   But I would probably use 30" long heatsinks for ease of mounting, but may not use the same LED spacing across the whole heat sink.

[DarinSchmidt]

this is what it looks like with 3 units 18" using 108 LEDs.



All these diagrams are based off of LEDs being 2" on center so however many LEDs you actually use based on the PSU will determine their placement and how many you use.

[Cole Harlow]

I run 35 3 watt XR-E's per fixture...  this is a std 90 gallon.   Maintain mostly SPS, and a few LPS in the darker corners.

The glass brace is probably not a problem, but I would avoid it.    Your going to need different intensities in your tank.  Not everything likes super bright.   So design in some darker areas and put the appropriate corals there.

I'm not sure I remember what you plan to keep in the tank?   How bright do you want it?   But I would probably use 30" long heatsinks for ease of mounting, but may not use the same LED spacing across the whole heat sink.

how many fixtures do you have? Id like to keep mainly lps and sps in my tank

[Wall_Tank]

2,  I will add a 3rd fixture when I upgrade to my 180

[DarinSchmidt]

i have a tank thats 96x27, 4 28LED units, i have LPS, SPS and softies

[Cole Harlow]

Ok just thought of a problem since i have 36 leds and three drivers how do i put the leds on a dimmer without having to put both blue and whites on the same driver could i alternate the blues and whites . Im trying to get a 15k to 20 k look on my tank should in just get 24 nlues and 12 whites ?

[Learning_The_Hard_Way]

Thats a problem that you can work around, your going to have to be more creative in your placement and run more wires.  I would just get another driver and run each on a seperate dimmer.  But.... if you want you can put blues on one, whites on one, and blues and whites sprinkled throughout on one and run it with the white dimmer so you can have a true blue led moon look.

[Learning_The_Hard_Way]

I just thought, you have XPG and XRE right? then they can run at a diff voltage, so make sure you set your driver at the lower ammount so you dont overdrive your XRE's

[Cole Harlow]

Im getting xp-g r5 white and xp-e royal blue

[DarinSchmidt]

what kind of power supply are you using?

[Wall_Tank]

Im getting xp-g r5 white and xp-e royal blue

Just curious why.  You said that you wanted more of a 14-20k look.   Why would you get your whites with more output than your blues?    I know that a 50/50 mix of the XR-E White and XR-E Blues will be pretty close to what you want.  If you go with the XP-G's, your going to need to experiment with the ratios.

[DarinSchmidt]

the only benefit to getting the xpg's are that they are more efficient, but i agree with wall, you are going to have to control the whites differently than the blues since they have different specs.

[Cole Harlow]

Could  i do 2 blues for every white that would make wirering everything easier

[Boonjob]

I Love the blue over the whites personally i think when i finally get aroudnt to making my lights i'm gonna have it so the whites can be turned off and on independently or have it cycle so many blues off and replace with so many whites when i feel i want more white in the tank.

[DarinSchmidt]

Yeah. You can do about anything that you want.

[Cole Harlow]

So about how many reds would you suggerst per heatsink

[DarinSchmidt]

i would probably suggest only 2-3, i think you would want the reds more for accenting and feeding the corals. Too much and it could really throw your colors off from what people are used to/like to see.

[Cole Harlow]

So my plan is to do 18 by 8 inch heatsink. There will be 9 rows of four leds. The first row of four will be all blue then a row of whites then 2 rows of blues another row of white 2 more rows of blues another white row and a blue row. Would this give me an even spread i dont plan on haveing optics on the whites. Next what else beside leds drivers fans and heatsinks would i need to do my diy led , resisters , circuit breakers.

[DarinSchmidt]

Do you want dimming or just on/off? What size tank is this going over? Tour setup is going yo probably be extremely blue. Tows of blue are ok but typically people stagger them. IF you are wanting to try something out, I would suggest supplimenting some blues and whites with a green, red, natural white, and royal blue. They will help bring out the colors in your corals and provide them a wider spectrum of photons. With as deep as typical tanks are ( less than 24") the color should reach the bottom. But use only 1 or 2 so it only enhances the colors. I'm working with Cutter yo do some experiments with all the XPE colors.

[Cole Harlow]

So my plan is to do 18 by 8 inch heatsink. There will be 9 rows of four leds. The first row of four will be all blue then a row of whites then 2 rows of blues another row of white 2 more rows of blues another white row and a blue row. Would this give me an even spread i dont plan on haveing optics on the whites. Next what else beside leds drivers fans and heatsinks would i need to do my diy led , resisters , circuit breakers.

When i said blue i mentroyal blue its going over a 210 gallon tank its going to be dimmable there will be three fixtures of 39 consisting of 24 xp-e royal blues and 12 xp-g r5 cool whites and 3 reds

[DarinSchmidt]

Ah yes. Sorry for some reason I thought this was a new thread. I would just try mixing some other color leds in there to get a better overall coloration in your tank. Since you are using RB leds add some blues, just a couple of each per fixture instead of so much blue color unless that's what you want. Its going to be pretty blue though IMO.

[Cole Harlow]

I was going for a 14k to 20k lokk woul i acomplish this with these lights the r5 whites are more powerful the xp-e royal blues right. Also does cree sell green leds if so where can you buy them

[DarinSchmidt]

Yes the XPG CW are more powerful than the XPE RB. Cree does sell different colors in the XPE series. Look up cutter leds.

[Cole Harlow]

I was thinking of doing 2blues 2reds 2 greens per fixture is that tomuch ?

[DarinSchmidt]

It will be a test, but i dont think so out of 36, should blend in well. The only other concern i had were the optics. Not sure if i would use the same optics and the more abundant white and RB or go with a wider one. This part (using colored LEDs) is still experimental for me.