Help with lighting errr Black Magic 101

[Dogbert4pres]

I have read... and re-read... then read some more and I am not able to get a grasp on lighting something not standard configuration like a "55g with LPS and leathers". The web has been of little use and the "Book of Coral Propagation" by Anthony Calfo allows me to spout off on 6500k vs 10k on types coral at 18"-24" and 24"-30" or PAR value requirements for SPS (and the tools needed to find the PAR value) but I have yet find a place that will actually tell me how many watts would be needed to light a 4'x8' runway using CREE LEDs 460nm and 6.5k or 10k much less what the spread would be if hung 12 above the water. Would a 48" wide light be needed, a 40, a 36 or perhaps 2 20s? Granted the spread would be a function of the hoods construction, but I would have thought a watts guesstimate could be at least documented. What I do get is a MH bulb for x gallons needs to be y. 3 watts MH = 1 Watt LED. So this process starts with a guesstimate then divides the result by 3 (a factor that is also a guess) and comes up with an answer which has to be as accurate as Shaq's free throw shooting ability. I am pretty sure a nice 30" hood with the correct Kelvin but at say 1200 watts would have me applying SPF 120 on the coral, something I am sure they (and the skimmer) would not like.

 

Enough of me spouting, too much reading made my eyes hurt. I guess it comes down to does anyone have some advice for a middle aged IT professional who is used to getting solid answers to problems quickly to what would be needed for a 48" x 96" raceway 24" deep. I had planned on starting off with the leather and LPS since they appear to be more attuned for beginners.

 

Thanks

[Brian Ward]

There's a lot of debate around how much LED lighting is actually required. The general recommendation, based on the actual experience of a wamas user is that 24-30 bulbs are required to light a 24"x24" area of a tank. Hanging 12" above the tank should give you sufficient blending but may not get enough PAR to the sand bed for things like maxima clams. The mixture should be about 2:1 Royal Blue to Cool White (XPG and XPE type). Dimmers are strongly recommended in order to adjust spectrum (color) as well as intensity.

 

For a 48"x24" area, about 50-60 Cree LEDs is appropriate. Expand that to 96" and you're looking at 200-240 total.

 

I see you're not a member, but we actually have a group buy running in the members area to purchase LEDs as well as components to build your own drivers. I strongly recommend you consider becoming a member. We have a For Sale section as well as a Group Buy area that can help you save some money. This is really a great community and you can get a ton of great information and help.

[Dogbert4pres]

Thanks for the reply, I just signed up, pretty slick operation... must be some fellow geeks in the group. Justin got a hold of me and suggested making this raceway 12" which is easily enough done.

 

How difficult is it to put a light fixture together? Seems I have a parts list from the response, at least the LED part and I am sure there is stuff not mention in the group buy.

 

Thanks

[Brian Ward]

Thanks for the reply, I just signed up, pretty slick operation... must be some fellow geeks in the group. Justin got a hold of me and suggested making this raceway 12" which is easily enough done.

 

How difficult is it to put a light fixture together? Seems I have a parts list from the response, at least the LED part and I am sure there is stuff not mention in the group buy.

 

Thanks

 

It's not too difficult. One member wrote a summary thread here:

http://www.wamas.org/forums/topic/38156-diy-led-questions-answered-here/

 

I'd read through that. You need an understanding of circuits and electronics but it's basically soldering together the LEDs and putting together the drivers or using commercial drivers.

[TonyD]

As a member, you also have access to people who have built these fixtures before and can help you. Where are you located?

[Swimboy123]

Welcome to the club!

[Dogbert4pres]

I am in Urbana Md, just a short hop across the river from you. My soldering skills would at best be comical, never having done this so I am not too keen on piecing one together. On the other hand though, I would not be limited to the sizes, both wattage and dimensions, that are in current production. I contacted some manufactorers in China and they can make a 180w hood with cree and 2:1, 6700:460 for $205US and another 60 for shipping making these pretty economical. They don't have a dimmer at that price so that is something to be concerned with.

 

Really the bigger concern goes back to the original posting, what is needed both wattage and length for a 8'x4' raceway. Does anyone in the group have something akin to this?

 

Thanks

[TonyD]

I have 72 CREE 3W LEDs over a 6' x 2' tank. It's 36 Cool White and 36 Royal Blue. I have 3 dimmable Meanwell drivers and 3 10"x20" heatsinks.

 

$205US from China seems like a good price, but check everything to make sure it's the real CREE 3W LEDs and not a knockoff. I paid well over $205 for my setup and DIY it myself.

[Brian Ward]

Wattage isn't a good measure because the lumens per watt vary dramatically based on the bin you choose. The spectrum also varies based on the bin.

 

For size, I'd go 6x2 at a minimum and probably more like 7x3.

[Guest thefishman65]

Output also varies a lot by the manufacturer which is why you need to make sure the manufacturer uses CREE (some are half as efficient). There is not easy way to verify it after the fact. For 4 feet by 8 feet, probably 192-240. You will also need HLG driver or something other than ELNs. I and many other will help you out in getting it build. If you decide not I or probably others could build it for you.

[Brian Ward]

Output also varies a lot by the manufacturer which is why you need to make sure the manufacturer uses CREE (some are half as efficient). There is not easy way to verify it after the fact. For 4 feet by 8 feet, probably 192-240. You will also need HLG driver or something other than ELNs. I and many other will help you out in getting it build. If you decide not I or probably others could build it for you.

 

Robert's offered to build for people. He's basically the expert here and over on ReefCentral, so I think his services are well worth it if you're intimidated about doing it yourself.