Bay Area Reefers

Where's the state of the art for household LED lighting at today and how does it compare to CFL bulbs?

how do i calculate led lights into my tank? i have a 50 gallon hex that is 22in from the water line to the sand. i want to run sps lps corals and more. any sugestions?

Why are the XR-E LEDs run at 1amp when cree states they should be run at 700ma, does this do any long term harm (shortening the lifespan) of the led or does adequate cooling asuage this risk? Has anyone run the XP-E on their tanks and if so how much cooling is necessary at 1amp for those LEDs (as I read they are more efficient...more light per watt than the XR-Es). Also never heard of a boostpuck. haha...more questions to come...

Why do you need a current fixed device (buckpuck or similar) with them and not simply a voltage source? Is it a matter of wanting to overdrive them at a fixed voltage (are you even doing that?).

How close can you pack these buggers?

Keep em coming I'll get to these tonight!

If we ignore lab prototypes....
It's a 2 part game. 1) the lumens/watt efficiency at a given temperature (kelvin rating) and 2) how efficient is the light delivery system.

Phillip's Energy Advantage t8 lamp at 4100k are about 95 lumens/watt (just looking at bulb power, not including ballasts/drivers etc as that is another issue). Cree's easily availaible warm whites of similar kelvin ratings are probably in the 85 lumens/watt range, and their higher kelving (6-7000k) brand new R4 XP-G's are probably 30+ % more efficient.

But the other part is lighting "extraction" and getting the light where you want. Fluorescensts are very floody and light everything...ceilings, walls....everywhere. LEDs are by design direction and can be used with optics. For spot lighting, LEDs kill Fluorescents. For broad room lighting, it varyies. If you don't care to light the walls and ceiling, then LEDs should shine.

Check this out:
http://www.creeledlighting.com/demos/LR6_Visual_Performance_Comparison.pdf

Also worth noting:
Cree Repeats as Lighting for Tomorrow Grand Prize Winner
http://www.cree.com/press/press_detail.asp?i=1253131315188

There is no "formula" like watts per gallon. However, A very rough estimate is you need 50% the power equivelent to MH for similar PAR (based on what I have gleened from others) Of course, YYMV with reflectors on MH and optics on LEDs, LED chosen, and ratio of LEDs. Most suggest optics for >18" tanks, especially with SPS. For AIO tanks, you ca generally run optics free. I'd crudely guestimate that you'd want something like 30 or so high flux LEDs with optics at 700-1000mA

The voltage-current curve isn't linear. A small change in voltage can have a large change on current. Also, the Vf of any given LED varies. One may have a Vf of 3.3V and another 3.6V for a given current. If you drive these two LEDs at 3.6V, you might toast the 3.3 Vf LED by dumping...oh..1.5A (just tossing out numbers) through it. Also, temperature effects current. At a fixed voltage, you can send different amounts of current through an LED at different junction temp. As temp goes up, the LED will draw more current...and heat up more..and pull more current etc. This is known as Thermal Runaway.

If you KNOW the Vf and want to drive a single LED, you can usually safely underdrive it with a voltage regulated source.

You have 2 limits. A thermal limit, and a bond wire current limit. I think that you can run upwards of 1.5 amps through the bond wires before they fry. The Junction (the die) is the other thermal limit. You CAN run at 1amp if you can effectively pull the heat away from the die. For all intensive purposes, this requires active cooling.

There are many many DIY projects using Crees, and many people driving at 1A. You'll have to hunt around NanoReef has a large and long standing following on these projects. There are also a few good threads o Reef Central.

A boosts puck raises the voltage so that Vout > Vin. (ie, you can drive 3 LEDs in series (>10V req) with 3V power supply. A buck puck does the opposite. Boost pucks are often more efficient but I usually see 350mA current limit ones on turn-key pucks.

Groovy Tony, Yeah I've seen that PDF before with the lighting comparison, don't know about pricing but I've seen some of those bulbs going off at upwards of $80 for a fricking bulb... well screw that! Not like I'm lighting coral yanno!

I ask because I saw a couple of LED flood lights at costco for around $10 or so, although they had what looked like the 5mm leds inside of them (maybe 50 or so?), but it was lacking on any information of output. They had a 3.5 and a 5 watt version of each. Thinking of doing some sort of recessed lighting in the living room, so thought maybe those would be useful, but who knows.. its costco I can get one then return it if I don't like it

All I would suggest is:

If you want to compare an $80 Cree light to a $10 LED light

1) consider output
2) consider color rendition
3) consider lifetime
4) consider efficiency
5) consider the $/lumen over the life of the bulb.

What you will likely find out is:
The output is way less
The color is way blue with a poor CRI (would you light your house with an 8K lamp with poor CRI?
Although the 3mm/5mm LED has a long theoretical lifetime, it isn't engineered for such and sucks in the lifespan department.
Efficiency is probably 50% of the cree

I just looked up a possible comperable lamp

http://www.besthomeledlighting.com/product/PAR30-SB-120-E27-W-60-W
Warm White: 3000K , 150 Lumens (compare to 15W)
120 Volts - 4.5 Watt
$24
Best case 150lumen/4.5 watts = 33 lumens/watt.

Cree LR6 3500K lamp with a CRI of 92 is
650lumens/12watts = 54 lumens.watt.
$80

For equal light, you need 4.3x of the 5mm light. 4.3x$24 = $103
For equal light, you need 64% more power.

I don't have lifetime info on the 5mm light.

Well its not about "equal light" it's about trying to justify a product to pay itself off, or at least come close, in a reasonable amount of time vs current CFL technology NOT incandescent technology (which I see a lot of the "Eco Bulbs" doing). Who knows maybe one of them would be a good fuge light