DIY LEDs - The write-up

[widmer]

Also, while we're talking electronics - can we talk about reducing fan speeds?

I bought 3 of the same 12v computer fan, rated at 0.12A current draw. I was going to wire them in series on my 24v supply to give them each 8v and quiet them down, but I think I'm already finding that this doesn't make them as quiet as I would like.

So I figured, what if I want to just give them each 6 volts, which means I would have to eat up another 6 volts: 24v from supply - (6 volts x 3 fans) = 6 volts left over

then 6v/0.12A = 50 Ohms resister necessary. But then I started thinking why am I guessing that 6 volts is really where I want to go to? And what if the published 0.12A current draw is not accurate, or there is some difference in current draw per volts across terminals? Then I took a cue from Kcress's thread http://www.reefcentral.com/forums/showthread.php?t=1751598&highlight=budget and figured why not use a variable resistor? So I found the same series that he suggests, but this one can go up to 250 ohms resistance:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AVT25-250-ND

It's $5.90. I'd like to just wire it in series with the fans and tune it in accordingly. Does my whole rationale make sense? If it does, then I suppose anyone in this thread who wants to adjust the speed of their fans could do it....

 

[Neogenocide]

If you shop on newegg.com, on a lot of their fans they have rpm, cfm, and decibal ratings, so you can pick from the quieter fans. I personally like the 120mm fans running at around 5 volts. Hardly noticeable.


Scott

 

[der_wille_zur_macht]

Question for anyone who knows electronics:

For those of us who are using buck pucks which are at least 18" from the power supply, and thus should be using a 50V, 220 uF capacitor across the buckpuck's input terminals(see buck puck data sheet on ledsupply website), does this capacitor fit the bill?

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P13131-ND

I basically singled in on it because it looks like it has the longest life span. But I don't know if the +/-20% tolerance makes any difference, being that we're pretty much all using 24V power supplies...

Clearly I'm not an expert but that cap is probably fine. the =/-20% isn't a big deal.

Also, while we're talking electronics - can we talk about reducing fan speeds?

I bought 3 of the same 12v computer fan, rated at 0.12A current draw. I was going to wire them in series on my 24v supply to give them each 8v and quiet them down, but I think I'm already finding that this doesn't make them as quiet as I would like.

So I figured, what if I want to just give them each 6 volts, which means I would have to eat up another 6 volts: 24v from supply - (6 volts x 3 fans) = 6 volts left over

then 6v/0.12A = 50 Ohms resister necessary. But then I started thinking why am I guessing that 6 volts is really where I want to go to? And what if the published 0.12A current draw is not accurate, or there is some difference in current draw per volts across terminals? Then I took a cue from Kcress's thread http://www.reefcentral.com/forums/showthread.php?t=1751598&highlight=budget and figured why not use a variable resistor? So I found the same series that he suggests, but this one can go up to 250 ohms resistance:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AVT25-250-ND

It's $5.90. I'd like to just wire it in series with the fans and tune it in accordingly. Does my whole rationale make sense? If it does, then I suppose anyone in this thread who wants to adjust the speed of their fans could do it....

I wouldn't use a resistor. You're gonna need a 1 or 2w resistor, which is going to be expensive (especially if you're thinking about a pot instead of a resistor for adjustability). At that point, might as well get one of those variable speed PC fan controllers, or even an adjustable voltage regulator. Or, DIY a PWM speed controller.

 

[widmer]

Thanks for the reply, that's a 25w variable resistor I've linked to though...$5.90. Do you suppose it will work? I did see those PC fan speed controllers for cheap on ebay too..but I don't know how they would respond in line with 3 fans on a 24v power supply...

 

[der_wille_zur_macht]

Good point, I didn't actually look at the part you linked to. And you're right, a fan controller meant for 12v use would probably freak at the 24v from your supply.

Honestly if 8v doesn't make them quiet enough I'd think about other fans. I've never had a fan that wasn't quiet enough at that voltage, and many fans start getting a little unstable much below that point (won't always turn on, run erratically, etc.) That's why PWM fan controllers are nice, they kick the fan with full voltage during the "on" part of the signal to keep them spinning even at lower duty cycles.

 

[crooks]

Can someone give me an idea on how many leds I would need for a 210 gal 72" x 24" 30"? Which lenses should I go with? The canopy is 24" tall and I can mount them anywhere. Can I also get a price estimate for everything with meanwell drivers?

 

[Altpers0na]

im guessin about 100?

 

[kcress]

widmer; Yes that resistor will work just fine. You are only trying to dump 3/4 of a measly watt.

But I concur with DWZM, the concern about the slow speed. Most fans are right on the verge of not starting up at the 1/2 voltage point. So what happens is people dial them down so they are happy - then proceed. Next power cycle disaster! As the fan(s) doesn't start spinning.

Also while it's nice to have dead silence from fans you actually need them to make some noise so you can easily detect their failure. If you want dead silence then you should include some over temperature protection for your system. Something that cycles the LEDs so it's seriously obvious and simultaneously prevents a meltdown.

IF you go with the resistor, set it where you like it then reduce it another 1V and see if the fans still start reliably. If they do then return the volt and proceed.

 

[widmer]

That's perfectly comprehensive, thanks.

Actually for a minute there, I was thinking I would just put some sort of random LED in line with the fans to both decrease the voltage pushing the fans and serve as an indicator of power going to the fans. But then I realized, what if it simply shorts so that the fan doesn't turn but the LED is still getting power?

So for now, as far as I know is that there really is no reasonable way to have the fans dead silent and still know they are running. Maybe if I want to get technical (from my point of view) in the future to overcome such a small difference in quiet vs silent, it will be another fun project to work on.

 

[cindre2000]

Quick question. I am thinking of replacing my 150w Par 36 pendant with LED's. The tank is 20"x20"; would 12 leds with 40 degree optics replicate my current lighting? Or should I go with 18?

 

[Neogenocide]

How high do you plan to hang your fixture?

If it's higher than normal, I would not use 40 degree optics, too narrow for a typical install.

Neo

 

[der_wille_zur_macht]

Can someone give me an idea on how many leds I would need for a 210 gal 72" x 24" 30"? Which lenses should I go with? The canopy is 24" tall and I can mount them anywhere. Can I also get a price estimate for everything with meanwell drivers?

That's 1728 square inches on a 30" deep tank (if I'm reading your measurements right - l*w*h). That's pretty deep. Assuming you want a typical mixed reef with plenty of light for SPS, I'd go with 150 LEDs, 700mA, 40 degree optics, and mount at least 12" up.

Prices will vary, but a good way to estimate a typical DIY build is to figure $10 per LED. So you're looking at ~$1500 for your tank.

That's perfectly comprehensive, thanks.

Actually for a minute there, I was thinking I would just put some sort of random LED in line with the fans to both decrease the voltage pushing the fans and serve as an indicator of power going to the fans. But then I realized, what if it simply shorts so that the fan doesn't turn but the LED is still getting power?

So for now, as far as I know is that there really is no reasonable way to have the fans dead silent and still know they are running. Maybe if I want to get technical (from my point of view) in the future to overcome such a small difference in quiet vs silent, it will be another fun project to work on.

I don't think a LED inline would work - Firstly there's the problem that the LED will probably want a different current than the fans. Secondly, you're right - when a DC fan stalls because of low voltage, it typically still draws power (just converts it to heat). If you wanted a failsafe, your best bet would be to get a 3-wire PC fan, since the third wire is usually a "stall detector" meant for this very purpose - technically it's a PFM signal indicating fan RPM, but you could probably monitor it for a lack of signal and interpret that to mean the fan wasn't running.

Quick question. I am thinking of replacing my 150w Par 36 pendant with LED's. The tank is 20"x20"; would 12 leds with 40 degree optics replicate my current lighting? Or should I go with 18?

I'd go with 18 or more at that size of tank. It'll be hard to get the right spread with only 12. How deep is the tank?

 

[rickb]

How do the optics attach to the stars? Glue or do they snap on?

Just ordered 96 LEDs and 8 meanwells for a 30x30x24 tank, do I need optics?

 

[cindre2000]

My tank is 16" deep. I currently can mount a light just under 24" above the tank; But if I use the ceiling, I can mount 4'+ away. And I really am not trying to get more light, I just don't want to replace bulbs, and I want a bluer look.

 

[Neogenocide]

How do the optics attach to the stars? Glue or do they snap on?

On my Cree's, they are snap on, however after messing with mine and having them on and off a few times, they would come off with the minimal effort and fall into the tank. So I ended up using just a bit of some white tacky glue on the bottom of them to hold them in place. If I ever need to remove them, it'll be easy to do.

Scott

 

[der_wille_zur_macht]

How do the optics attach to the stars? Glue or do they snap on?

Some glue on, most snap on, some are two pieces - one piece glues, the other snaps. You can just follow the instructions for yours. if it's not obvious, ask the vendor you got them from.

Just ordered 96 LEDs and 8 meanwells for a 30x30x24 tank, do I need optics?

That's quite a lot for a tank that size. I don't think you'll need optics for intensity's sake, unless you are using a low drive current. Depending on how high you mount the LEDs, you might want them just to prevent light spill.

My tank is 16" deep. I currently can mount a light just under 24" above the tank; But if I use the ceiling, I can mount 4'+ away. And I really am not trying to get more light, I just don't want to replace bulbs, and I want a bluer look.

At 24" 40 degree optics would be OK. If you go to 4', you might want to start looking for really tight optics (I know there are some 9's out there - look at flashlight modding sites.) Though, at that height, the light is going to be extremely directional - not a bad thing, but don't plan on putting corals in spots where they'll be shaded, because your shadows will be DARK.

 

[widmer]

How do the optics attach to the stars? Glue or do they snap on?

Just ordered 96 LEDs and 8 meanwells for a 30x30x24 tank, do I need optics?

This probably doesn't apply to anyone but myself yet, but the 6 degree optics from LEDsupply are really pretty hokey, in that they have some sort of sticky surface which is supposed to hold them on, and they definitely weren't made to go over the Crees that are mounted on stars, due to the fact that the adhesive covers all of the +/- terminals and overhangs the whole star... I'm going to have to be drilling them and somehow reattaching to make them fit...

 

[der_wille_zur_macht]

This probably doesn't apply to anyone but myself yet, but the 6 degree optics from LEDsupply are really pretty hokey

I'm guessing you're talking about the Dialight optics, and not the Cree brand 6 degree optics?

 

[bstohrer]

First, thanks to all the pioneers on this and the other LED DIY threads for all of the ideas!
I'm planning to switch the VHO (6 X 160 watts) system on my 135 (72" X 18" X 24") to and LED system. I keep mostly SPS along with a few LPS and softies. I plan to use around 48 XRE cool whites and about 48 royal blues powered by dimmable Meanwells. I have a nice oak canopy I wish to keep. The down side is it only gives me only 4" clearance above the tank and about 4.5-5" max above the waterline. A stacked configuration of fans, heat sink, LEDs, optics (maybe) and splash guard will be doable but tight fit. Instead of the traditional finned heat sinks, I'm thinking of using 72" long aluminum bar or channel stock. I'll likely use 3 or 4 72" sections. Also, rather than dedicating individual fan(s) to a heat sink, I will use a number of fans in the back of the canopy to generate "œgood" airflow over the tops and bottoms of the aluminum bar "œheat sinks".
I also plan to be able to move the individual bars forward as needed along with the capability to angle the bars forward or back allowing me to fine tune light distribution.
The bar stock is available from a number of vendors in a large number of sizes. I ordered a some 3 foot sections from www.onlinemetals.com. I ordered a 2" X 0.25" and a 2" X 0.375" bar along with a 1" X 1" X 0.125" thick channel.
I have 12 XREs along with a Meanwell and a selection of optics on order and I plan to put together a 3 foot section and do some temperature measurements at different drive currents and at different airflows. I'll also place it over a section of my tank just to get an idea of the looks. I will drill a tiny hole through the bar where the center of one star will be. I will then insert a 0.5mm temperature probe along with some arctic silver into the hole and in contact with the back of the star. While this will not be a true junction temperature, I hope it will give me some idea of the heat generated. I'll post results in a few weeks
Has anyone seen any "œback of star" temperatures with setups using finned heat sinks with fans?
Any comments or suggestions would be appreciated.

 

[widmer]

Correct. I ordered the LEDs with optics at the same time, and without prior experience I didn't know what to expect really, although now in retrospect it's pretty easy to see how the base of that optic is formed.

Had I known beforehand, I would have probably gotten simple lenses on dealextreme such as those for flashlights, and coupled them with basic male/female PVC screw connections, in order to create very simple optics for which you could change the beam width ie from 5 degrees to 80 degrees by simply screwing the PVC connection, and changing the distance of the lens from the LED. I would really encourage someone else to try this though... Maybe I will in the future, but for now I just want to get this fixture up and running...