Aquarium LED light

[krap101]

Hi, I'm planning on making a light with 12 Cree XR-E Q2 WC leds, and I'm wondering if this will work out. I want to use a Meanwell 60W 15V 4A driver, and make 3 strings of 4 LED's. I want the leds to run around 3.7V and 800ma, or close to 3W.

 

[blasterman]

Should work fine, and your math is right on.

Not sure what you plan on growing in the aquarium though. A bunch of WC bins is pretty bland, although they look good on fresh water.

 

[krap101]

Thanks for the quick reply

I wanted something near 6700k, and I wasn't sure how it was going to look. this is going over a 10 gallon tank, and I'll just use the heatsink to keep everything together.

I wasn't sure of how different colored leds would work in series or in parallel with eachother, but something is telling me that I'd need another driver. If I maybe get a 5500kish bin, that runs at 3.7V, I'm assuming that they'd be able to be in series together...

From what I understand, the white leds are basically blue/uv leds with a phosphor coating, which means that they work essentially the same way as fluorescent lights right? Will the WC's give my plants enough spectrum, or will I need to mix in some WD's or something?

 

[blasterman]

For freshwater you should be fine. Cool-white LEDs are heavy in photosynthetic blue light, and the plants will take up the spectrum they need. You can mix blue LEDs in the strings equally with the white because they have the same forward voltage, but blue doesn't do much for fresh water like it does for reef.

Aethestically, all cool-white looks terrible on a reef tank, but looks vibrant on a planted fresh water tank. I have a guppy breeder 30gal, and my 5600k Bridgelux looks incredible for cobra guppies.

 

[krap101]

I posted on a fish forum, and one member told me that meanwells can not run parallel strings. I'm just checking before I go ahead and buy it, because nothing I read said anything able that.

Also, I'll have an extra .8 amps unless I decide to add another string. The meanwell will control this right? Or will it just depend on the dimmer and leave the possibility that I fry my leds?

 

[blasterman]

I have no problems running parallel strings off MeanWells. They're likely worried about being blamed for current mis-matches with poorly balanced LED strings and causing burn-outs.

However, I didn't know you didn't have the power supply yet. IMHO, it makes no sense getting a 15 volt 4amp driver when a 48volt 1amp driver will work just as well.

Most of the 48 volt MeanWells can be adjusted to around 44volts or so, or the constant current models can be adjusted either way. The 48volt driver should be able to handle a dozen R2s with no problem and all be in one series. Makes wiring pretty darn simple.

Trust me - you wont want to add more light to twelve Q2s on a 10gal freshwater tank.

 

[krap101]

If I'm using a dimmable meanwell, wouldn't that mean that the voltage must be kept constant?

 

[blasterman]

The constant current Mean Wells have both a voltage and current adjustment. Typically you leave the voltage maxed and adjust the current range because it's more flexible. However, this assumes you're running a single strand of LEDs. With a 1amp constant current driver it's not to hard to guess where to trim it to 700mA or so. Also, a 48-volt / 1amp driver is fairly inexpensive.

I also use the fixed voltage supplies because they're cheaper, and just use a voltmeter to find the right range. Only problem is they aren't sealed like the LED drivers and a single water splash will toast them.

On one hand Mean Well discourages parallel configs like you said, but what in the world would you do with a 5A constant current driver?

 

[krap101]

The reason I decided on the 15V 4A meanwell is because that left the least amount of volts unused (I think it was .2V), which means that I could run the meanwell slightly above it's "rated" voltage, or run the leds very slightly under their "rated" voltage. Maybe I'm still thinking in resistances etc, but less wasted voltage=less resistance=less heat, which may or may not be negligible.

I was thinking this was a good fit, assuming parallels work

http://www.meanwelldirect.co.uk/pro...with-Dimming-Function/ELN-60-15-D/default.htm

I could go the 48v route, but I'm still wondering what makes parallels difficult? I've taken the electricity and magnetism course, but haven't had any hands on experience yet (or very very little, that can't really be applied here, since it was in a "lab" setting).

I'm also wanting to build a light for a 29 gallon and a 40B, so I'm wanting a somewhat upgradeable design, and preferably one driver maybe two I guess. The most I can run off of the 15V and 48V are 12 leds at 800ma. For the 24V, I can run 18 leds (3 strings of 6), but I've only been looking at this line of meanwells, as this is what was recommended to me by a guy on another forum. I think I'm wanting 1 led per maybe 12-18 in^2, and my 10 gallon has 200 in^2. My 29g has around 360 in^2 of surface, and the 40 has ~650 in^2. Assuming I do this at the high end of the "lighting spectrum", then I'll need 20 leds for the 29 and 36 for the 40B. For the 40B, it looks like the best solution is two 24V's, and for the 29, maybe I'll just go with 1 24V, and just go with slightly lower lighting.

This is looking good so far, and looking easier than I originally thought.

Do you have any ideas on a moving sun-type using an arduino and a rtclock? Or maybe some way to control the brightness/dimness of the leds with a timer? Maybe this will be too big of a hassle...

 

[blasterman]

I really don't mess with dimmers much other than initial power tweaking. The crew at Nano-Reef forums spend a lot of time messing with this and can give you ideas on how to do gymnastics with the 10volt external dimming circuit the higher end Mean Wells have.

For me, I plug my driver into simple on/off timer and am done with it. My arguement being we never had dimmers on our halides and T5s, so it's just an aethestic thing.

Lighting requirements for freshwater planted aquariums are substantially lower than reef. Just how much lower though I'm not really sure. What I do know is simple cool white looks really good.

With high powered LED lights it's just a good rule of thumb to use the highest voltage supply you can and avoid parallel strings as much as possible. Lots of smaller parallel runs just don't make sense with drivers up to 48volts available.

 

[blasterman]

Also, I gotta ask why you're messing with XR-E's for this? (unless you already have them).

XP-Gs way outclass XR-Es and you could likely get away with half of them. Four Bridgelux 400s would also match the out-put of a dozen XR-Es at about the same price per emitter, and can be spaced in the middle of the tank eliminating the need for optics.

 

[krap101]

Price was one thing, and spotlighting is another. Generally it's better to use more leds at a lower power than more leds at higher. It looks like the xpg's will put out about 2x the lumens, but I'm sure it will be less at 800ma. I bought my XR-E's for around 3$ each, and for that price, it wasn't hard. The first led that came up on a search was a XPG R5, which was around 10$.

Anyways, I've changed my design a little, and was wondering on input.

I've changed from the 15V 4A to the 24V 2.5A so I can more easily add some fans. I'll have two strings of 6 leds at .8A so I have around .9A that I can play around with. Since my tank is probably well to over lighted right now, I was wondering about the fans and possible moonlighting options.

If I put two fans in series and in parallel with the other two strings, will it screw them up? From class we learned series have the same amperage, and parallels have the same voltage. Each string will eat up 24V, so that won't be a problem, but will it screw with the other strings when it ramps up the speed? If that's a problem, couldn't I just fix the current draw of the fans somehow?

Also, rather than using a heat sink heat sink, it was suggested to me that I could just use an aluminum plate, and I was wondering what thickness I should get, or if I should just go with a traditional heatsink?

 

[blasterman]

I'm assuming you want to add a couple 12volt fans in series, right? Shouldn't be an issue, except that I found a single low RPM 120mm fan on 45watts of LEDs (15x3) was overkill on a big sink. Even that single fan keeps a 12x7" heatsink ice cold. However, the sink gets hot when the fan is off. It's amazing how much cooling a low RPM 120mm fan does.

Plus, if you keep the fans on the main light circuit the fans will power off when the light does. No need to keep them running all night.

I would do a moonlight on another circuit. Use a spare 12volt wall wart or something.

Generally it's better to use more leds at a lower power than more leds at higher.

That sounds like the 'kool-aid' dispensed by the Cree fanboys on reefing forums. It's totally untrue and the based on the lack of higher powered Cree emitters and making up rules to justify it, but you already have the emitters :thumbsup:

 

[krap101]

I ordered them the other day. I need two fans to get the 24V, so I might just use 2 80mm's or something. It's about the same price, and my tank is only like 12" deep, so I don't think high power will matter as much.

thanks again

 

[krap101]

I'm getting ready to buy my meanwell, and I'm wondering which would be better for dimming, the vdc model or the pwm model? As these meanwells are built specifically for leds, I'm assuming that they flicker at a range above that which we can see (around 60hz in the periphery)

 

[blasterman]

I've used both current regulated Mean Wells explicitly for LED use, and their regular fixed voltage versions for LEDs. I've never noticed flicker with either, even when dimmed down, and I'm really sensitive to flicker.

 

[krap101]

What would I need to do to add the dimming function? I was reading that I need to add some board or something?

 

[blasterman]

I can't help you with ther external dimming versions. I prefer to set mine with the trim pots and leave them alone.

There's a ton of info on this in the reefing forums. Googling 'mean well external dimming' will keep you busy for a few nights.

 

[Illum]

For freshwater you should be fine. Cool-white LEDs are heavy in photosynthetic blue light, and the plants will take up the spectrum they need. You can mix blue LEDs in the strings equally with the white because they have the same forward voltage, but blue doesn't do much for fresh water like it does for reef.

you could consider a smaller version of this,notice how blue LEDs are used in between whites?
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1587273

for power supplies, use a supply thats rated 30% more than what you are planning to pull out of it, it'll help lengthen its life