DIY LED Questions

Hello,

So basically this is my dilemma. I have a 70 gallon tall tank (30 inches deep) that I would like to move from the current halides over to a LED fixture. It is a 36" long tank so I figured doing two 17.5" heat sinks with 24 LEDs each would suffice. (I may be wrong?) I have being doing some research and it seems the majority of DIY projects use a 2" spread on the LEDs with a 60-65 degree optics on them, using Cree blues and white in an alternating pattern. After speaking to a rep from Ecoxotics about this tank, they said I would be best served using additional 453nm blues in order to achieve maximum penetration at those depths. Back story finished.;D

My feeling on the situation is basically this;
Go with a few extra LEDs on the same 17.5 inch heat sinks, but on a tighter spread (say 1.25 inches) and use 40 degree optics to get a more "spotlight" effect from each individual LED, while still getting smooth and consistent coverage overall. While adding in additional 453nm LEDs to the mix for the claimed increased penetration. (Those being the additional LEDs used to create a tighter spread, I was thinking 6 additional per heat sink)

So... would this be a decent solution to my tank depth problem? Or a total waste of time/money?

Any additional comments, or schooling me on LEDs would be a good thing, and highly appreciated.

Thanks!
-Andrew

 

I don't think you need 40deg optics, personally. 60deg should do you alright. The problem with 40, as you seem to be aware, is you'll need them very close together or you'll have to mount the light a considerable distance from the surface (I'm thinking around 30").

I am a little confused as to your discussion on the blue LEDs. Are you saying 24 of your LEDs would be plain blue, and only 6 royal blue (~450nm)? I wouldn't do this. I would do a max of 24 royal blues (RBs) and a max of 24 cool whites (CWs). You could sub out some CWs for a few warm whites (WWs) also.

I just did the conversion myself a few weeks ago. You can check my build thread here: http://www.3reef.com/forums/i-made/diy-dimmable-rapidled-kit-converting-mhs-96138.html

 

I read through that, it was part of the catalyst for the decision to move over to LED. I had planned on doing 24 CWs and 24 RBs as well as an additional 6 RBs per 17.5 inch heat sink. Thus netting me a total of 30 LEDs (12 CWs 18 RBs) per heat sink, on 5 Meanwell drivers. I did not however realize that the Cree RBs were in the ~450nm range, and I am not sure the additional 6 would be needed? I am hoping to keep them mounted approximately 8-12 inches above the waters surface, would 60 degree optics be acceptable at such a distance? Also, for instance; the ecoxotics modules would net me 96 LEDs, vs my current DIY would only have 48-60. What is the difference here?

And one last question. More LEDs on a tighter spread = more par at all depths? Or would I just be adding more LEDs with little to no benefit?

Thank you for your reply! I am glad someone finally answered ;D

 

A 14K look IMO is 1:1 ratio. A 20K look would be 2:3 white:blue. I have a 14 LED setup on a similar sized heatsink, and have 6 white to 8 blue. I would say right now that I am somewhere inbetween 14K and 20K, but the color is perfect for what I wanted. I went with the XP-G Whites, as they put out more lumens...however, they need more drivers per amount of LEDs than XR-E.

The difference between a DIY CREE setup and the Ecoxotics would be cost. It is going to take at least 96 Eco's to match the brightness of 30 CREEs. I have 4 RB XR-Es as night lights on a 28" deep tank and it lights the tank up like they are daylights. If you haven't seen these in person, they are BRIGHT...and with optics, they focus the brightness even more. A plus to the Ecoxotics are all the different options you have spectrum wise, and you can move them around like T5 bulb placement to get the right balance.

I would take a look at ReefLEDLights.com for their heatsinks. You can get a 30" long x 8+" wide heatsink, and be able to space out your LEDs, with 60 degree optics as suggested above, all on 1 heatsink. Getting 35" worth on a 36" tank is going to waste all LEDs on the sides, most of the light will be wasted on the glass or outside the glass.

 

Yes, CREE Royal blues are in the 450-465nm range. However, CREE blues are in the 465-485nm range, hence my confusion. Don't use regular blues, just use royal blues. Your additional six really aren't necessary, unless you're after a 20k look as FaceOfDeceit pointed out.

Also as FaceOfDeceit said, you do not need 35" of heat sink on a 36" tank. 30" would probably do you just fine. Any more and you're going to waste whatever is on the ends.

I still would use 60 deg optics. If you are really limited to your distance from the surface, you'll probably need a fair number of LEDs with 60deg optics because you'll have to mount them close together. That being said, I think 60 LEDs is probably overkill for your tank. 60 on my tank (60 x 20 x 24) is more than I need. If I ran them at full power, I'd probably bleach all the corals in my tank.

Yes, more LEDs will equate to more PAR at depth, but it won't be a linear relationship.

Finally, the big difference in the Ecoxotic LEDs and the CREEs is wattage. CREEs are 3 watts. I'm not sure what the wattage of the Ecoxotics are, but they most definitely less. That's why you can't compare # of LEDs to # of LEDs.

What makes you say this? I don't believe this to be true, at least for the meanwells.

 

What I mean is with XR-E, due to the mA, you cannot put as many XP-G in a string as you can with XR-E. 1050mA vs 700mA. You wouldn't necessarily need more drivers, just make sure the correct current is going to each type. Some drivers are also designed for the XP-Gs.

 

Still a little confused here. I'm running 2 meanwells each with 12 XP-Gs. I'm running them at 1.45A max. XP-Gs can handle up to 1.5A, XR-Es can handle up to 1A. Yes, you must adjust the meanwell according to what type of CREE, but you can still run up to 14 LEDs of either XP-G or XR-E per meanwell.

 

What are you running your XR-Es at? Not the same current I assume. That's all I was saying. You can't run both from the same driver (unless the current is lowered, which defeats the purpose). Hence, you would need more drivers to run them.

 

Ah, yes, then I completely agree. I have the XR-E strings set to 950mA max.

 

Thanks so much for the input, it helped immensely. The more I learn about this stuff, the more overwhelming it seems

So I am assuming when you say "fair" amount of LEDs, I would be fine using the 48 LED kit with dimmable drivers from rapidled.com? What would you recommend as far as spacing on the heatsink is concerned? 1.5", 2"?