Multichip LED's vs. array of LED's question

[aiq25]

Hello. I'm new to saltwater and only had my saltwater tank for about 2.5 months. I don't have any corals but in the future I would like to add some. I would like to use LED's for lighting. I'm thinking of keeping soft and LPS corals but I think I might want to keep SPS, not sure though.

I was doing some research on LED lighting systems for reef aquariums and I stumbled upon multichip LED's. I was thinking about using 20W LED's to start off with. 4 blue, 4 royal blue and 4 white for a total of 240W. Currently I have a standard 55 gallon tank and I think this might be too much light for the corals I want to keep but I will control the intensity using PWM. But after doing some research it seems like some people recommend using single high power LED's in arrays vs. the multichip because the multichip will create an spotlight effect.

I haven't built a canopy yet but I'm planning on doing it and the lights will probably be 6-18" from the top of the water. I think using the multichip might create a spotlight effect, so I'm thinking about going with 3W high power LED's. To start I think I will use a computer PSU to power the system. Maybe in the future I will get a better PSU unit. I don't think I will go above 100W average power but not sure. Also, in the future I'm thinking of upgrading to a 150 gallon tank (a wider tank than my current 55 gallon), so that's why I would like to have 250W to 300W lighting system.

So my question is what which one should I go with? Sorry for the long post but I thought I would explain my question thoroughly. Any advice is greatly appreciated.

 

[perkint]

Personally (and there are lots of ways to do it) I would run constant current drivers on separate LEDs. The arrays I have seen work out more expensive than buying the equivalent LEDs on 20mm stars. Running them on separate stars will also spread the heat out more, as well as the light.

Most people use the meanwell LDDs. If you go that way, using a computer power supply is probably going to cost a fair bit as don't they do 12V max? That means you'd need a driver for every 3 LEDs! One or two higher voltage power supplies (56V max) would not cost much.

Makes it easy to add a controller for PWM, not worry about wasting energy on resistors to control current, no danger of blowing the LEDs due to too much current (unless you put the wrong LDD on!) and it leaves you with a fairly simple, versatile and scalable system

As said, there are lots of ways of doing it, but that's what I'd do.

Actually, that's a lie. I am using one of O2Surplus' 5up boards with his driver and arduino built in, but, it's still similar

Tim

 

[aiq25]

Personally (and there are lots of ways to do it) I would run constant current drivers on separate LEDs. The arrays I have seen work out more expensive than buying the equivalent LEDs on 20mm stars. Running them on separate stars will also spread the heat out more, as well as the light.

Most people use the meanwell LDDs. If you go that way, using a computer power supply is probably going to cost a fair bit as don't they do 12V max? That means you'd need a driver for every 3 LEDs! One or two higher voltage power supplies (56V max) would not cost much.

Makes it easy to add a controller for PWM, not worry about wasting energy on resistors to control current, no danger of blowing the LEDs due to too much current (unless you put the wrong LDD on!) and it leaves you with a fairly simple, versatile and scalable system

As said, there are lots of ways of doing it, but that's what I'd do.

Actually, that's a lie. I am using one of O2Surplus' 5up boards with his driver and arduino built in, but, it's still similar

Tim

Would you recommend 1W or 3W LED's? I'm thinking I need 3W LED's. Also, I'm thinking about using the Meanwell drivers to control the LED with PWM. I actually have a LED driver circuit I have used before with PWM control for brightness. I used a PIC microcontroller for the PWM signal in that application. Not sure if I will try to use that circuit but I might, it did work and I have some parts left over to test out the concept. For the power supply I'm thinking about designing my own but I might buy one. 48V seems like a better voltage to work with, so the connections for the LED's will be made easier. lol

Since my tank is 48" long, I'm thinking about making two fixtures, each 24" long. That way in the future when I upgrade my tank I can add two more 24" fixtures and I will have 4 fixtures that will be independent of each other. Being independent will allow me to position them differently, if it's needed. A modular design seems like a better idea than going with one 48" long fixture.

 

[perkint]

Personally, I'd use Cree XML2s where I could get them in the colour I wanted (cool/neutral white), XML if not XML2 (eg high CRI whites seem to be available in XML but hard to find in XML2), XTEs for Royal Blue and XPE for Blues. So I'd actually go for 5 or 10W LEDs, but then only drive them at 2W or less.

Under drive LEDs and you get more light for your watt and a lot less heat

Tim

 

[jedimasterben]

The XM-L and XM-L2 have pretty inconsistent color, in addition to bad off-axis color. Using optics sorta negates that, but I would still use a better LED.

In addition, buying the XM series to run at 700mA or less is just dumb IMHO. They offer less than 20% more flux than the XT-E for ~200% the cost.

To the OP, if you use a computer power supply, you have three voltage rails to work with - 3v, 5v, and 12v. The only usable one with the LDD is the 12v rail, and it leaves you with ~9v to work with on the output, which is less than three typical '3w' LEDs.

 

[aiq25]

Personally, I'd use Cree XML2s where I could get them in the colour I wanted (cool/neutral white), XML if not XML2 (eg high CRI whites seem to be available in XML but hard to find in XML2), XTEs for Royal Blue and XPE for Blues. So I'd actually go for 5 or 10W LEDs, but then only drive them at 2W or less.

Under drive LEDs and you get more light for your watt and a lot less heat

Tim

I read somewhere that the amount of current the LED receives can affect the wavelength of the light... So wouldn't under driving them from 5W to 2W change the wavelength? Or does that not matter?

 

[jedimasterben]

I read somewhere that the amount of current the LED receives can affect the wavelength of the light... So wouldn't under driving them from 5W to 2W change the wavelength? Or does that not matter?

Bad information.

 

[aiq25]

How far away should I space the LED's? I'm trying to draw a sketch of where to place the LED's. I'm thinking about spacing them 3" from each other (center-to-center).

 

[jedimasterben]

Don't space any different colors away from each other. Have multiple clusters of LEDs to reduce color banding, putting any distance between them will be the same as hosting a disco in your tank.

 

[oreo57]

I read somewhere that the amount of current the LED receives can affect the wavelength of the light... So wouldn't under driving them from 5W to 2W change the wavelength? Or does that not matter?

Err.. partially correct:
T

he established solution is to eschew analog dimming in favor of a digital technique such as pulse width modulation (PWM). Manufacturers claim the use of PWM ensures that LEDs will be immune to color changes during dimming.

However, recent research suggests this is not the case because different PWM duty cycles change the junction temperature of the LED; and junction temperature itself is known to alter the color emitted by the chip (the "œchromaticity").

http://www.digikey.com/en-US/articles/techzone/2014/feb/led-color-shift-under-pwm-dimming

Overheating and aging also occurs in phosphor coated LEDs.. (i.e. all white ones).......

Phosphors are sensitive to both temperature and high-radiative
flux. Generally, more than one phosphor is used to obtain a
given color temperature of the PC LED. If one phosphor were to
depreciate more quickly than the others, a color shift would occur that could render the light
quality unacceptable without affecting the projected life. This emphasizes the importance of
manufacturers' providing color quality metrics on life tests as their products age after 6,000
hours.
"¢ Since temperature plays such a significant role in product life relative to color quality, the
construction of the LED and the associated thermal management system of the lamp must be
optimized to dissipate the heat. Poorly designed systems will only contribute to accelerating the
color shift process.
Proper design can result in a product with minimal color shift for the useful life of the product.

but it really isn't worth bothering about at this level and scale..

 

[aiq25]

Don't space any different colors away from each other. Have multiple clusters of LEDs to reduce color banding, putting any distance between them will be the same as hosting a disco in your tank.

If I have multiple clusters of LED's, isn't it better to have multichip LED's with a heatsink? I never really thought about the disco effect. lol

 

[aiq25]

Thinking something like this. 12 x 3W for each cluster will give me total of 108W for the this module. I will make another module the same way. Each cluster will have it's own PWM driver, so I can adjust the brightness as needed. Any comments/suggestions/feedback?

 

[perkint]

The XM-L and XM-L2 have pretty inconsistent color, in addition to bad off-axis color. Using optics sorta negates that, but I would still use a better LED.

What better LEDs would you suggest? And can you qoute a source of the off colour issue? I am not an expert, but I was under the impression that Cree's binning codes were about the best out there. A lot of suppliers don't quote the full code so you can get differences there, but that's a supplier issue, not a fault with the Cree LEDs.

In addition, buying the XM series to run at 700mA or less is just dumb IMHO. They offer less than 20% more flux than the XT-E for ~200% the cost.

Sort of agree with that - XTEs work out a much cheaper initial purchase, but they cost more watts per lumen and they also put out more heat per lumen so you need bigger heat sinks and pay more in energy. Maybe more of an issue here in the UK (since we have sh!t selection of cheap heat sink suppliers and possibly (?) pay more for electricity) but it's still worth being aware of.

Tim

 

[perkint]

Thinking something like this. 12 x 3W for each cluster will give me total of 108W for the this module. I will make another module the same way. Each cluster will have it's own PWM driver, so I can adjust the brightness as needed. Any comments/suggestions/feedback?

Feedback? Yeah, I'd mix the colours up. As mentioned previously, unless mounted well above the tank, you'd see the separate colour effects.

Tim

 

[jedimasterben]

If I have multiple clusters of LED's, isn't it better to have multichip LED's with a heatsink? I never really thought about the disco effect. lol

Not really, unless you want to buy a lot of very expensive multicolor multichips and spread them out running at low currents.

Thinking something like this. 12 x 3W for each cluster will give me total of 108W for the this module. I will make another module the same way. Each cluster will have it's own PWM driver, so I can adjust the brightness as needed. Any comments/suggestions/feedback?

You'll definitely not want to run them like that. This is a 55 gallon tank, right? So 48"x12"x21" is the size.

You'll want a minimum of four clusters of LEDs. If you're set on using '3w class' LEDs, then you'll want to use 12x neutral white, 24x royal blue, and 6x blue for the entire tank using quality LEDs (no eBay, I would recommend Luxeon Rebel & Rebel ES). The numbers you're suggesting is just nuts lol. Those are your base colors, to have a 'full spectrum' array you'll want to add 4x cyan, 12x violet, and an experimental addition for better color rendition would be PC-amber Luxeon Rebels, 4x of them.

What better LEDs would you suggest? And can you qoute a source of the off colour issue? I am not an expert, but I was under the impression that Cree's binning codes were about the best out there. A lot of suppliers don't quote the full code so you can get differences there, but that's a supplier issue, not a fault with the Cree LEDs.

Sort of agree with that - XTEs work out a much cheaper initial purchase, but they cost more watts per lumen and they also put out more heat per lumen so you need bigger heat sinks and pay more in energy. Maybe more of an issue here in the UK (since we have sh!t selection of cheap heat sink suppliers and possibly (?) pay more for electricity) but it's still worth being aware of.

Tim

Anything Philips, their color is loads better than the Cree that are sold by any of RC's sponsors and any others selling non-specific bins of Cree. If you're also worried about lumens per watt, then I would recommend to use four Bridgelux Vero 10 LEDs, 4000K bin. At 350mA, they emit 1180 lumens at 9.3 watts, which is ~126lm/w. The XM-L2 running at the same wattage emits 917 lumens for ~98lm/w. Considering that the Vero 10 costs ~$4.75 versus the XM-L2 at ~$8.75 each, in addition to the Vero smashing the XM-L2 in terms of color, the XM series is an all-around poor choice.

If you want to use the Vero series (I would recommend them, they're awesome), then use 4x of the BXRC-40E1000-B-03 at 300mA, 8x Luxeon M royal blue at 700mA, and 8x blue Rebel at 700mA for your base colors. These will be adjustable if moving to a larger tank, as the Luxeon M and Rebel can be run at an amp (giving 35% more light) and the Vero 10 can be run up to 700mA (giving 118% more light) for better penetration.

 

[aiq25]

You'll definitely not want to run them like that. This is a 55 gallon tank, right? So 48"x12"x21" is the size.

You'll want a minimum of four clusters of LEDs. If you're set on using '3w class' LEDs, then you'll want to use 12x neutral white, 24x royal blue, and 6x blue for the entire tank using quality LEDs (no eBay, I would recommend Luxeon Rebel & Rebel ES). The numbers you're suggesting is just nuts lol. Those are your base colors, to have a 'full spectrum' array you'll want to add 4x cyan, 12x violet, and an experimental addition for better color rendition would be PC-amber Luxeon Rebels, 4x of them.

Thanks. Yea it's a 55 gallon tank. I'm just curious... Why more royal blue than regular blue?

 

[jedimasterben]

Royal blue is your primary source of blue. Think of cool blue as the color of windex - too much of it and it just looks damn weird.

 

[perkint]

The XML2s do vary a lot in output depending on the bin, but certainly I have been struggling to find any decent bins with high CRI

The veros are definitely very impressive. For what I'm after tho, I just wish they did a vero 5

Might have to get some 10s for a play, but it means changing my power supply

Thanks for the reply

Tim

 

[MorganAtlanta]

I'd consider buying a couple Chinese royal/white Bridgelux units then swapping out LEDs if you want, and putting in electronically dimmable drivers or PWM dimmers. You can't buy the components for as cheap as you can buy a fixture these days, and it will save a lot of soldering.

 

[jedimasterben]

The XML2s do vary a lot in output depending on the bin, but certainly I have been struggling to find any decent bins with high CRI

The veros are definitely very impressive. For what I'm after tho, I just wish they did a vero 5

Might have to get some 10s for a play, but it means changing my power supply

Thanks for the reply

Tim

You really won't find any XM-L or XM-L2 that are decently binned unless they are special ordered from Cree, which none of the 'typical' sources do.

A vero 5 would actually be awesome but I dunno how they could make them much smaller, check out the size of the Vero 10!

I just wish they could get the voltage down just a liiiiitttle bit - with 26v even at 300mA you can only run a single one per LDD driver unless you run them in parallel, which is what I'm doing with mine. I normally don't recommend parallel due to danger to the LEDs with too much current or with thermal runaway, but keeping the current low enough so the LEDs can tolerate 100% and keeping them on the same heatsink will help to alleviate issues with that.

What power supply are you using? I thought you said you were going with 48v?

I'd consider buying a couple Chinese royal/white Bridgelux units then swapping out LEDs if you want, and putting in electronically dimmable drivers or PWM dimmers. You can't buy the components for as cheap as you can buy a fixture these days, and it will save a lot of soldering.

And then you have sub 60lm/w efficiency (since most Chinese white LEDs put out 120lm or less) and color ranging from decently inconsistent to flat-out garbage.