Brightness of your DIY LED arrays

[lordofthereef]

This may not be the proper section, but since it is related to DIY LED builds I decided to ask here anyway.

I am running 2 strings of 12 LEDs on dimmable meanwell ballasts over a Biocube 29. I have no par meter so I am sort of flying blind here. What I would like to know is what percentage people are running their strings. This is for SPS/clams.

I get polyp extension at 15% and at 60% (talking dimming/brightness here) so I am unsure where to set it (I haven't wanted to go higher than this as I don't want to burn my corals). I CURRENTLY have my blues set to 65% and whites set to 45% (I liked the color that produced). They ramp from 0% to their respective numbers over an hour and a half and then ramp back down over that same amount of time at the end of the night. Total hours of light at full brightness is about 8, plus the three hours of ramping (1.5 in the morning + 1.5 at night).

So with that long-winded explanation, I'd like to hear from those that are keeping a similar tank about what your dimming is set at, how many hours you run them, etc.

[rysher]

how were you able to ramp 0-100? 0-10 doesnt work on PWM.

[lordofthereef]

That's simply how the ALC works (reefkeeper module). You get no light until you hit 10. From there they ramp to 65% and 45% (RESPECTIVELY). Interestingly, on their way down, 0-10 seems to work fine. LEDs get VERY dim down to 1 and then go out completely at 0.

In any case, that wasn't really my question...

[lordofthereef]

Bump

[lordofthereef]

Bumping again.

[btldreef]

okay.. i ll try to give you some input.

i have 120 3w crees on my 180g. 2 controllers audrino boards, for blues and whites.
my settings are 90% blue and 65% whites. as far burning corals.... i haven't had any issues thus far.. but i did acclimate my lps and softies and try not to place them directly under the leds. i also do not run optics for that reason. all the dimming does is change the kelvin/color not the par of the leds.

[hvacman250]

I have 120 Cree XPG and XPE over a 220 (72x24x30 deep), about 14" over the water with 60* optics

If I go over 70% (via Apex) bad things happen.

[lordofthereef]

all the dimming does is change the kelvin/color not the par of the leds.

is this an accurate statement? Everything I've read states that dimming is a good way to acclimate the corals. Is it really all just for looks?

[Spaced Cowboy]

is this an accurate statement? Everything I've read states that dimming is a good way to acclimate the corals. Is it really all just for looks?

I don't see how it can be. If he's using an arduino for control, he's probably using PWM to do the dimming, and in fact he may even be using my/DWZM's CAT4101 design. If you're using PWM, you're switching the LEDs rapidly on and off, using a constant current driver set to some fraction (normally 0.7x) of the rated maximum throughput of the LED.

PAR is a measure of incident radiation within a fixed frequency range. The LEDs emit radiation within that range, and if they output a given PAR 'X' at maximum output, when run at a duty-cycle of 50% ("half brightness" in dimming terms), it stands to reason that the PAR would be halved as well. Either that or I've seriously misunderstood how PAR works (it's measured I'm photons-expressed-in-moles per meter-squared per second, which looks like an irradiance unit to me, old physicists trick - if you want to know what's going on, always check the units :) )

Of course, if he's running some sort of analogue dimming, the logic for reducing PAR still works, but the rate of PAR reduction will now be a function of the LEDs power-efficiency curve, because you'll actually be putting less current through the LEDs, rather than driving them in switched mode. I still don't see how that would alter the colour temperature, though. The way you do that is to dim two different spectral outputs (eg warm white and royal blue LEDs), changing the relative intensities of each. It's the relative change that affects the perceived colour tempature.

Simon.


PWM dimming runs the LEDs at full-output, then nothing, then full-output, then nothing, ad infinitum... The ratio between the 'full-output' and 'nothing' stages determine the duty-cycle. A duty-cycle of 100% means it's always 'full output'. A duty cycle of 0% means it's always 'nothing'. A duty-cycle of 50% means the time spent on 'full output' is the same as the time spent outputting 'nothing'. Since the circuit switches on and off several thousand times per second, we perceive it as gradual dimming as the duty cycle reduces, but given that is how PWM dimming works, it's easy to see the PAR must divide by 2 if the duty cycle divides by 2.

[lordofthereef]

^ That is how I understand it as well (however I have understood things wrong before!). I am using PWM for dimming, as mentioned before.

[lordofthereef]

I have 120 Cree XPG and XPE over a 220 (72x24x30 deep), about 14" over the water with 60* optics

If I go over 70% (via Apex) bad things happen.

Can you elaborate? What are said "bad things"? Are we talking unwanted reaction from the livestock? From the equipment?

[Adam_T]

Elos Mini 20 gallon cube (17x17x17)

I had a DIY fixture over it at first, 12 LEDs (6 Cree XP Cool White, 6 XP Royal Blue), with no optics. Going past 75% (SPS, LPS, Softies) and the corals would keep closed. Fixture was hung 6'' above water level.

NOW

I have a AI Nano over the same exact tank, and I have them setup to ramp up to 30% Blue/Royal Blue and 26% white. This fixture has 40/60 degree optics, so I don't want to go nearly as far up as I did on the DIY fixture. Once I get my PAR meter in, I will see where I truly want to keep the dimmers set to....I'm thinking somewhere around 45/40. Fixture mounted 5'' above water level.

[[17]shawn[17]]

over my 45 cube i have 36 3w crees 18blue@ 700ma and 18white@1000ma with 66/55 optics the light is about 13" off the water

when i first added the unit i completly bleached all my coral running at 100%blue 80%white. led light may not vissibly look as intense as MH so you have to be carefull you dont run them too strong. to this day my coral is still recovering almost 6months later and my light is now running at 70%blue 50%white its still plenty of light and my clam is happy down 18" on the sand

not sure if that helps

[lordofthereef]

Thanks for all the input so far.

My setup is in a stock hood, so the bulbs are probably 3-4 inches off the water without optics. Everything looks healthy, I am just trying to optimize here. I suppose I am attempting to see what intensity provides the best growth without blasting the corals with too much light. I suppose it is entirely possible that I hit the sweet spot. All of these corals and the clam came from a tank with 250w mh and supplemental actinics. The transition just seemed too easy, and nothing ever seems this easy in the hobby, which is what got me wondering to begin with.