Have you seen this article?
- Thread starter fragit
- Start date
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Oddly enough, I have.
http://www.reeftank123.com/lighting/strohmeyer_article.html
I pass this out to all new to lighting.
I hope Mr. Strohmeyer gets residuals.:)
http://www.reeftank123.com/lighting/strohmeyer_article.html
I pass this out to all new to lighting.
I hope Mr. Strohmeyer gets residuals.:)
dacianb
Active Member
I wouldnt took everything written there as a fact...
Voltage doesnt affect LEDs spectral emission (ok, have a tiny influence, but is so small that can be disconsidered - 0.01 nm range), there is no spectral difference between constant current and PWM method to drive LEDs,
Osram NP blue designed special for reef light? I think is a marketing lie from TMC - such led doesnt exist anywhere else then related to tmc. Ahhhh... it is OSLON Signal, converted blue?? This is a signaling LED as name define and ... whatever, I am tired reading such compilations of infos from all around the web and unfiltered at all.
Sadly, so many consider them as holy references.
Even the IP classes are not OK...
Voltage doesnt affect LEDs spectral emission (ok, have a tiny influence, but is so small that can be disconsidered - 0.01 nm range), there is no spectral difference between constant current and PWM method to drive LEDs,
Osram NP blue designed special for reef light? I think is a marketing lie from TMC - such led doesnt exist anywhere else then related to tmc. Ahhhh... it is OSLON Signal, converted blue?? This is a signaling LED as name define and ... whatever, I am tired reading such compilations of infos from all around the web and unfiltered at all.
Sadly, so many consider them as holy references.
Even the IP classes are not OK...
TheEngineer
Formerly icecool2
I will admit to not reading the whole article yet and I certainly would agree that not everything in every article is 100% fact. I do feel compelled to correct some of your statements though.
As to the effect of voltage on spectral emission, you are incorrect. Here is an example for a blue LED. A 30mA difference results in a 3nm shift in wavelength. Before anyone says, "But mA is current, not voltage", Ohms law is V = I*R. The resistance stays the same here, so if you change I, you change V.
I saw their statement about driving with PWM versus constant current. I want to re-read what they said here, but again there is truth in this statement. Controlling a driver with PWM vs constant current should have no effect. Driving the LED with one versus the other is quite different.
I don't know about the brands they specified or the specific products. So I have nothing to add there.
dacianb
Active Member
I will admit to not reading the whole article yet and I certainly would agree that not everything in every article is 100% fact. I do feel compelled to correct some of your statements though.
As to the effect of voltage on spectral emission, you are incorrect. Here is an example for a blue LED. A 30mA difference results in a 3nm shift in wavelength. Before anyone says, "But mA is current, not voltage", Ohms law is V = I*R. The resistance stays the same here, so if you change I, you change V.
I saw their statement about driving with PWM versus constant current. I want to re-read what they said here, but again there is truth in this statement. Controlling a driver with PWM vs constant current should have no effect. Driving the LED with one versus the other is quite different.
I don't know about the brands they specified or the specific products. So I have nothing to add there.
Your graph is a 50 mA max LED, which nobody probably use on a tank. On modern, good quality LEDs shift induced by whatever current / voltage is next to nothing (see pictures below, which are from Oslon Signal LCB CRBP - probably the one made for reefs ;)) . There is slightly higher deviation due to temperature, but still what a regular user will never see.
I dont bet that no name LEDs can have much larger shifts, but everywhere in this article is about "top brands"...
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TheEngineer
Formerly icecool2
You are almost certainly correct that higher end LEDs will be less susceptible to these variations. However, if we look to chromaticity as you have provided, you must consider this specifically in the wavelengths that are of importance to corals, particularly in the 400-500nm range (give or take). The spacing between these colors is quite small. You can see in the chart below how quickly the absorption drops off for both Chlorophyll a and b. Missing the mark by 5nm is quite severe in terms of efficiency.
Temperature, as shown in your second image, is a huge factor of course. Especially over the LED lifetime.
Temperature, as shown in your second image, is a huge factor of course. Especially over the LED lifetime.
dacianb
Active Member
I just gave an example... I use different leds on my system anyway. You are right on the drop, but please consider that LEDs don't emit a single wavelength. The numbers we see everywhere are peaks only, but total emission curve is defined by "Spectral bandwidth at 50%" factor which can be 20-30nm for colored led, much more for phosphor converted leds. In the end any led emits energy in a total bandwidth of 30-40nm, so couple of nm shifts on temperature / voltage factors doesn't matter at all. Much larger deviations you may expect from pure binning of LEDs. For example each led light manufacturers claim same 450nm lights (the ones we love), but certain types of LEDs, different manufacturers have various ranges of wavelengths. The famous 450 nm led can be anything between 440-460 (peak).
Buying a fixture with 10 LEDs (most probably unbinned) there are chances that between extreme leds to have more than 10nm difference. In this way will have a wider bandwidth covered all the time, even small shifts occur :)
Buying a fixture with 10 LEDs (most probably unbinned) there are chances that between extreme leds to have more than 10nm difference. In this way will have a wider bandwidth covered all the time, even small shifts occur :)
LostInTheDark
Active Member
I started a thread a few weeks ago asking the difference between "Black Box" LEDs and higher end products like Kessils. At least this article helps me understand why I have so much trouble with my Ocean Revive lights all the time. If I read something like this a couple of years ago I probably would have saved the money and gone big. Now I'm stuck with lights that constantly burn out and shift spectrum.
dacianb
Active Member
Indeed, we should stop; I was just a bit ticked off by such articles made in a weird way to hide a clear marketing message (by accident, a certain led light was waay superior to any other) and I just tried to warn people that is not quite accurate and should be well filtered.
As a small secret, I am a professional led lighting designer since 20 years almost, working for most advanced fields as medical, aeronautics and military. I have inventions in LED lighting and also I am beta tester for top LED manufacturers... I am testing leds in a way that not even manufacturers dont..... So I know limits of each and every model on market.
By the way, did you knew that not all leds can survive a sudden airplane cargo decompression at 10 000 m?? :D
dacianb
Active Member
There are so many rules to make a good light, that a single forum post cannot cover them. Pity that people cannot see real technical aspects of a light beyond marketing leaflets.
In general :
- don't use a LED at full power - with few exceptions, no LED can survive this and efficiency is dropping a lot. If a led is rated at 1A, use it at 0.75 and so on. You may have lower output at 1 A than at 0.75A. Dont believe the 50 000 hours either - there are specific needs for a led to survive this. Also can go at 100k or 150k hours rather easy.
- If you can touch a LED board after few minutes at full power is a great test on a light - Keeping LEDs in this area makes them happy. If is hot> 50-60°C.... less efficiency, less lifetime and dont expect to use them at all at 100%
- please don't believe that a collimator increase the efficiency of a led. Just gather the total energy of the led in a smaller area and measurements looks more impressive, but with 10-15% losses (Fresnel law). Tanks looks awesome with uncollimated leds (anyway, they have primary lenses with 120° beam, so you will not loose light on ceiling) - everything stays in the tank, more uniform and you can put lights lower without problems.
- what will happen with your expensive light if the cheap fan breaks?
- And list can go on and on, but will stop. If have questions, just ask :)
TheEngineer
Formerly icecool2
It would have been too much of a coincidence. :) I've visited them in Leuven. I still work with them on some expansion ideas.
SB Reef Lights
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So how much Chlorophyll B is in most chloroplast with in the zooxanthalae in our corals? If your chasing B you'll be chasing it a long time. Clade C is present instead, however density of population is low in corals (though higher in clams) so chasing its peak yields minimum ROI. In fact hitting the cartenoid peredinin has more effect at the 490-495nm wavelength than going after chlorophyll C. Folks post the absorption chart often yet fail to factor in density of each Clade of Chlorophyll, not to mention Chlorophyll B is not present in the coral's dinoflagellates. Hit 420nm, 447nm, 495nm with a little 660nm and you're good to go. The rest is aesthetics. There are secondary, third and forth absorption points for Chlorophyll A, B and the cartenoids but again ROI is minimal.
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