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Unread 04/07/2009, 05:53 PM   #651
stugray
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Ok I have been trying to calculate the quantity of LEDs to equal my reef lighting and the numbers are just not coming out right.
I figured if I posted my calcs someone could point out what I am doing wrong.

So:

Lets say I have ~1000 Watts of 15k Metal Halide lighting ( nice round number )
From what I can tell online, numbers for "effective lumens per watt" for MH is ~70 lumens/watt.
This assumes 80% reflection efficiency.

So my tank of 1000 watts should have ~70,000 lumens

Now for a CREE XR-E Q5 driven at 0.75A outputs ~220 lumens with no "reflection factor".
These are 3.0 Watt devices being run at 2.25 Watts.
So that is ~98 lumens/watt.

So to get 70,000 lumens I need:

70,000 / 98 = 714.

So.... according to these rough estimates, I need ~700 LEDs @ ~$6 a piece = $4200

Even if I get a price break to $3 apiece, thats still $2100 not counting drivers or heatsinks.

Where did I go wrong in my calcs or assumptions above?

People seem to be getting much better results with their setups.

Stu


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Current Tank Info: 125 Gal. display w/80 gal mud/caulerpa sump. Basement sump w/ LED Grow Light,Gravity fed Reeflo200 skimmer w/ ORCA Recirc, DIY calc reactor & kalk stirrer. Inline plumbed 75 Gal frag/settling tank.
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Unread 04/07/2009, 06:07 PM   #652
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Stu, I think the main benefit of LEDs is that they lend themselves more easily to optics, and getting more usable light into the tank, not because they put out more lumens per watt. I don't think you should worry about trying to equal the same total lumen output of the halides.

LEDs don't have the advantage in luminous efficacy, as your numbers show (at least not enough to offset costs, its marginal at best)

To see where the benefit comes from just look at how much light an MH bulb spills outside the tank, even with a great reflector. Sure the reflector captures most of the light above the bulb, but its still going to be illuminating equally in all direction from the side not facing the reflector...... whereas a lambertian LED is inherently a downwards cone already, albeit a very very wide diffused one.

The spread might be 120 degrees or more, but the main hotspot is still directly below the LED even without optics or a reflector. More downward rays.

Then if you raise the LEDs up higher and add the optics, you are pushing most of the light from the LED into the tank, instead of at the glass, out into the living room etc. Makes it really hard to use the total watts or lumens to compare the two.



I think if somebody put an MH bulb into a projection lens housing like LFP did with xenon bulbs.... it would be enough light to melt corals.


One thing your math demonstrates is that the advantage of LEDs does NOT scale linearly. For example (very contrived!) if you had a tank that was say 100' by 100' x 10'.... it might be lit with 50x50=2,500 1000w halides (based on a halide lighting a 2'x2' area)

The "wasted light" I referred to before would only really be wasted for the lights on the perimeter of this tank... 50+50+48+48=196.

So for the remaining 2304 bulbs "the wasted light" would be thrown into the tank and helping light the corals.

Though there would still be light lost from light entering the water at an angle vs LEDs which could have all downward rays. But arguably the scattered rays might be desirable.

Yes I realize nobody would design a tank that way, but it shows how the benefit of LED's is more of an "edge case".


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic

Last edited by ReefEnabler; 04/07/2009 at 06:21 PM.
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Unread 04/07/2009, 07:05 PM   #653
ReefEnabler
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something just occured to me,

why did you include lumens per watts when doing the following calculation:

Quote:
70,000 / 98 = 714.
You are saying that means you need 700 LEDs.. when I think it means you need 700 watts worth of LEDs.

Why not

70,000lm / 220lm = 318

Since you know the LED puts out 220 lumens, wouldn't 318 * 220lm = 70,000lm? I thought the lm/w only comes into play if you were to compare how many watts you end up with after using 220 LEDs vs 1000w of MH.

318 * 2.25w = 715.5w

So 715w of LEDs to get there vs 1000w of MH...

715/1000= 0.7155

Check against your lm/w figures:

70 / 98 = 0.7142
pretty close!


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic

Last edited by ReefEnabler; 04/07/2009 at 07:12 PM.
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Unread 04/07/2009, 07:15 PM   #654
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widmer; Of course not knowing what a DIYer will really attempt I can't say "absolutely no problem". But 'fundamentally' yes! A piece of square aluminum tubing would probably work great. But since it is enclosed and the inside surface would essentially be thermally unexposed, not available for heat rejecting there would be better shapes, like U-Channel. Alternatively if you mounted the tube vertically stack effect would have the air whipping thru the inner space and this would greatly improve things. Of course blowing air thru the center would really provide nice cooling.

ReefEnabler; The miter saw idea would certainly provide more cooling. Put the miter cuts where you aren't mounting the LEDs and that would be a pretty nice deal. Probably using U-channel and mitering it would be even better than square tubing. (with no fan)

stugray; Oh for sure Stu! Water cooling would certainly do the trick. Of course you then have to have a radiator somewhere, and fans probably, and a pump maybe... The usual hassles a 'water cooler' has to contend with. Probably not a lot of push for that since LEDs, while they can get pretty hot with a few watts of waste heat, aren't in the same league as a Itanium. An Itanium is a case where a much smaller surface area is belting out 120W of heat. That's just too hard to carry away on a small finned heatsink, but can easily be carried away on a little water. Be neat if you had a use for the warm water. Most the time we're trying to cool our tanks because of the lights! So when the lights are on we want no heat. You need an insulated storage tank to store the LED heated water in so later that night you could use it to heat the tank. LOL

As for your HM/LEDs question... It's an interesting question.
I think its really hard to equate the two. Apples to oranges sort of thing.
Reflectors are notoriously ineffective compared to optics. The fact that MH is what's called a 'distributed source' as compared to an LED being a 'point source'. makes a large difference -large enough to allow cheap optics.

Also as ReefEnabler points out using light smarter by not having any hit the glass or spill into the room is a huge advantage completely unavailable to MH. I would 'guess' you could cut MH lumens in half to have equitable lighting of a narrow rectangular area. But that's only a guess.


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Unread 04/07/2009, 07:34 PM   #655
stugray
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ReefEnabler,

Ahh! you are right. 98 is the lumens per watt of the LEDs, but they put out 220 lumens PER LED!

So it should be: 70000 / 220 = 318

Much more reasonable!
Thanks I knew it was simple ( see what working 3rd shifts does to your brain during normal daylight hours ;-)

However that means we still need 714 watts of LED power to equal my 1000 watt system ( for equal lumens ).
But you are right, the LED lumens are far more effective than the MH lumens.

Now I could imagine making three "modules" with 100 LEDs each.
More 'doable'.


kcress,

I thought the water cooling might be effective with the CPU coolers. They are fairly inexpensive and I bet you could find an aluminum extrusion with water channels integrated.
Just screw the fittings on each end and youre set.
The only worry is that I dont know what kind of liquid to run, distilled?

And I knew about the advantages of the LEDs I was just trying to get a ROM of how many it would take to be comparable to my current setup in raw lumens.

Stu


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Some people think that I have Attention Deficit Disorder. They just dont understand that........ Hey! Look a chicken!

Well, We KNOW GOD exists, but for US to exist without a GOD is preposterous….Umm wait a minute…. Sounds a bit circular to me…

Current Tank Info: 125 Gal. display w/80 gal mud/caulerpa sump. Basement sump w/ LED Grow Light,Gravity fed Reeflo200 skimmer w/ ORCA Recirc, DIY calc reactor & kalk stirrer. Inline plumbed 75 Gal frag/settling tank.
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Unread 04/07/2009, 07:51 PM   #656
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Sounds good... I think 300 of those LEDs will be insanely bright .... But if you're going to make them all dimmable thats not such a bad thing. definitely wouldn't need optics


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic
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Unread 04/07/2009, 08:29 PM   #657
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Liquid cooled would be... cool. You could have the heat exchanged in another room such as the attic or basement or wherever you wanted the heat instead....

Would need an overheat shutoff switch in case it malfunctioned, I guess.


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Unread 04/07/2009, 10:02 PM   #658
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It's a thoughtful idea, but I don't believe liquid cooling is suited for this application. As far as I know, liquid cooling is primarily for when you need to pull a lot of heat out of a tiny area quickly. This is not the case with any light pendant. A typical pendant has got a lot of area, completely open for ventilation, and doesn't produce heat that rapidly. The extra stuff necessary for liquid cooling just wouldn't be worth it unless you're doing it for fun.


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Unread 04/08/2009, 12:58 AM   #659
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Here's an example of what will work for 350mA HPLEDs, air cooled.

Keep in mind you'd probably need a little more for 500s, more yet for 700s, and a lot more for 1000s.

Note the two holes on each leaf are for the star hold-downs. The cuts are for a little better convection cooling. The radial tabs are for mounting the whole thing, (only two or three were needed). The center hole was for this light fixture's hold-up.

Also note that each 'leaf' could be bent or twisted in several directions, at the narrow spot, to aim the LEDs appropriately.

I did this with a router, (CNC).

[IMG]http://i41.*******.com/155gjyw.jpg[/IMG]


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Unread 04/08/2009, 09:51 AM   #660
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does anyone have any hands on exp. with these 1000w led torches???? i could see these mounted in a ceiling on a rimless tank looking sick.......btw great thread everyone.....
http://www.rebreatherworld.com/rebre...led-torch.html


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Unread 04/08/2009, 10:06 AM   #661
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Kcress- That's pretty cool. It would be really fun to see it in action. What were you going to use it for? Also, what are the bands with a hole in the end for?

troylee- Looks like fun. I would be surprised if it actually consumes 1000w of power, to me it looks like that's just the model name. My line of reasoning is if I'm not mistaken, at the bottom of the page he's saying that his 21w HID is brighter...


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Unread 04/08/2009, 10:13 AM   #662
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I think he was saying that those were for mounting purposes...


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Unread 04/08/2009, 10:14 AM   #663
ReefEnabler
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I was thinking the same thing... if that was really 1000 watts worth of LEDs it would have to be sooo much brighter than the 21w HID. But still awesome.


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic
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Unread 04/08/2009, 11:42 AM   #664
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i saw in the xenon thread someone posted a 100w 15k led......where can i find these????? im sure it's in this thread but i skipped around and can't find it.......i work at a lighting and sign company and have played with led's alot but that thing looked sick i want one.....i actually set up my moonlight's with r.g.b. which allows me to dial in the colors and temps via. a dmx controller from boca flasher that i stripped from a sign lol.....


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Unread 04/08/2009, 11:48 AM   #665
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I recall what youre talking about, I think it was the Edison Opto 100w "LED". or it might have been one of the OSRAM 100w street lamps...

These are actually not "100w leds", they are a bunch of separate LED dies packed into a really small space. thats a case where something like water cooling might start to make more sense.


http://www.led-professional.com/content/view/464/56/

no idea where you can get them, I looked too any found nothing. maybe its only available overseas or through special suppliers?


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic
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Unread 04/08/2009, 11:53 AM   #666
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ya thats the one.....same here can't find them anywhere......there is a guy i forgot his name but he has one and some blue 15w around it.....pretty sick looking.....


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Unread 04/08/2009, 11:56 AM   #667
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Lookie here

http://cgi.ebay.com/ws/eBayISAPI.dll...54&refid=store

150 bucks for 6000 lumens... not bad!! no idea if its the same brand...

probably could light stuff on fire with 3 degree optics (duno if there even is optics for this type?)


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic
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Unread 04/08/2009, 12:27 PM   #668
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Kind of makes you wonder if they're soon to replace halides -

It's got ~the same efficiency, potential to tailor the spectrum, is a single point-source lamp, is very close to halide price, and it'll basically never burn out so it's a huge money saver...

In fact I'm sure that if it did come in a bluer spectrum, early adopters here at RC would have already replaced their halides with it. Then after the early adopters show they work great, the landslide comes...



Last edited by widmer; 04/08/2009 at 12:34 PM.
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Unread 04/08/2009, 01:33 PM   #669
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ya thats it..... i see my 220 would get really expensive to light being i think i would need at least 8 of them.......but it would be a good project for the aqua pod....


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Unread 04/08/2009, 02:49 PM   #670
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Quote:
Originally posted by widmer
Kcress- What were you going to use it for? Also, what are the bands with a hole in the end for?

It was used in a commercial art luminary.

Mounting the unit. Since the material was already there I just made lots of mounting points.


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Unread 04/08/2009, 03:01 PM   #671
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Guys,

Any opinions on this fan: http://cgi.ebay.com/120mm-Fans-4LED-...3A1%7C294%3A50

It's cheap, but I'm no FAN expert :-) It should work on this application right?


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Unread 04/08/2009, 03:51 PM   #672
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Those will work just fine. I used the same Logisys fans but in blue.


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Unread 04/09/2009, 10:09 AM   #673
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Too bad there just isn't a feasible lens combination for the luxeon rebel royal blue LEDs to project a ~10deg beam. Because otherwise these have the absolute best amount of light produced per $ (if I understand the conversion correctly, see below).

http://www.luxeonstar.com/luxeon-reb...00ma-p-162.php

But once I couple them with the $5+, 6degree lens and the mounting plate, they're more than $10/LED which is a little outside of my price range.

I'd love to know if I could attach these lenses to them:
http://www.dealextreme.com/details.dx/sku.1920

But with such tiny scale optics, it would most likely prove to be impossible.

BTW can anyone confirm my understanding of how to convert "mW lumens" to lumens for comparison reasons?

As far as I can tell it's just 683*(mW designation in units of W)

ie the 525 mW lumen LED will be 683*.525=359 lumens?


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Unread 04/09/2009, 10:26 AM   #674
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Windmer something to consider is the Rebel LEDs by themselves are TINY!! 3mm x 4mm wide... look even smaller in person. they definitely require experience with reflow soldering and some kind of hot air station... though there is a guide on reflow soldering with a toaster oven... sounds tricky

http://www.instructables.com/id/Toas...Soldering-BGA/

For some reason Endor doesn't do the Royal Blue TriStars

These III Stars do 340 mW for $6.82.... Its not as much light/$ as the rebels, but you dont have to reflow, and your optics would be simpler.

http://www.luxeonstar.com/luxeon-iii...00ma-p-286.php


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Current Tank Info: 220g Display, 70g sump, 35g frag, 50g fuge, 2x250w MH, 1x400w MH, 2x80w T5, 2x140w VHO Actinic
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Unread 04/09/2009, 10:28 AM   #675
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I'm pretty sure manufacturer specs determine lumens per watt. Look online for data sheets for the LEDs you plan on using. Cree has all of their information in PDF form on their site.


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