Question for the EE's out there and anyone else proficient with power supplies.

[Midwest Express]

I have been out of electronics for too long to remember off the top of my head if I can use certain electronic parts laying around for other projects.

I am going to build a LED lighting system for my new 17 gal cube and then eventually for my 125.  My question is on the supply for the LED array...

How hard would it be to use the power supply from a computer for an LED array or is that just overkill?

I am just not sure what is so special with the power supplies that everyone is using for their LED setups.

[Wall_Tank]

A Computer power supply is way overkill, also the voltages are a bit too low and you would need a way to limit the current.

LED dedicated drivers are current controlled.    But you can do it voltage controlled.    The first thing you need to determine

1)  Do you want to be able to automatically dim the LED's?   If yes, then you need to look at a dimmable LED driver.

They typical LED that is used for Reef applcations is

3.3-3.5 vdc
350ma to 1ma.

[Midwest Express]

I'm looking at using a mix of these:

http://www.ledgroupbuy.com/bridgelux-neutral-white-4500k-6-pack-1-99ea/

and their royal blue leds.

It is a 16"x16"x16" tank but I am looking at getting a 10"x10" heat sink.  That should hold 12 LED's.  That should be enough for that small of a tank correct?  I am not worried right now about the fixture being able to be dimmed.  Is there a reason why I would want these to be able to be dimmed?  This is for my desktop mini-reef.

Edit Addition:

What parts am I looking at for this? LED's, driver, heat sink, power supply?  I know that the LED's are current driven... just not sure what size power supply I need to supply the LED's. 

[Wall_Tank]

For half a 90 gallon tank, I ran 35 LED's.    That was for SPS.   If you are doing softies you can do less.

I have not seen the Bridgelux LED's, everyone here is using the Cree's..    But the theory is the same.     For a 12 LED setup, that is going to need something like a 60 watt driver.   The bridgelux's max out at 700ma, so you may need to fuse the string so you don't overdrive them.   
The other thing to note is that the Bridgelux comes with built-in 60 degree optics, you may need to have to put more LED's on the system to avoid banding.   

Dimming is done so that you can adjust the color of your tank.   Typically setup with Whites on one driver and blues on another driver.   Also for sunrise/sunset.

[cyberwollf]

I think You can get 24 volts if you go from the -12 to +12 leads on the CPU power supply.  if you have one laying around its a free 600+ watt supply.  If you dont need it to be dimmed you can just balance the current with resistors to get the right amperage.  It can be done on the cheap, just depends if you want to lean DIY or just buy the working dimmable supply.

If you have the stuff already and want to, I would.

But if you would have to go buy a CPU supply, Id say its not worth it.

[Midwest Express]

I have a 460w brand new laying here, but I found some kit bundles that are pretty good priced based on what you get.  Cree LED's and all.  So I will probably just get one of those that include dimming controllers.

Thanks for the help guys!

[Blown76mav]

Something like this???

http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/

[cyberwollf]

Something like this???

http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/

Yep, I run several of those at my house for projects.  Makes a stable VDC source 10x cheaper than desktop supplies. you can pull +-5 and +-12 off them

[Blown76mav]

I use mine to charge my LiPo's in my Rc cars.  Bought the power supply online for 15.00 WAY cheaper than the 70-100 they want for a store bought one.

[Boonjob]

Guess I need to learn more about this rofl... I have agazillion power supplies just sitting around... I would like to add LED's to my new corner tank.. never though about using a comp supply to power them though...

Would it relly save that much more money?

Any benefits of dimming the leds? It seems like as long as they were on and growing things I would be happy...

[Midwest Express]

The more I looked into it, I am going to go with two dimming controllers so that I control the spectrum I want.  I am going to try to get into the 12k to 14k area.  Those are my favorite ranges but I also want to be able to control the temp of the light to promote growth.  Sooooo... I will figure out what range helps my corals out the most and then at night when I am around the tank I will have settings marked so I can change it to the temp I like looking at it.

I am thinking about getting this kit with an additional controller.

http://www.rapidled.com/servlet/the-59/12-Ultra-Premium-LED/Detail

Those should be enough for my little tank.

As for the power supply instructable... how I love that site!  I have quite a few psu sitting around the house and a couple brand new ones.  Now I can have a psu for building and testing things again.  Thanks!

[Reefpete]

Any benefits of dimming the leds?

Dimming is done so that you can adjust the color of your tank.   Typically setup with Whites on one driver and blues on another driver.   Also for sunrise/sunset.

And no, cody I'm not just quoting random posts.

[Boonjob]

I meant any physical benefits, growth, bleaching, etc... or is it just appearance only based....

[jd]

Cyber: You kill you're current with a -12 and+12V setup, I think. the -12V is usually only an amp or two. Also- I'm not dead! I just jump in to correct Wes. :p

[cyberwollf]

Cyber: You kill you're current with a -12 and+12V setup, I think. the -12V is usually only an amp or two. Also- I'm not dead! I just jump in to correct Wes. :p

Figures... Now that you mention it, i think the negative leads do list only a few amps.... I just cut them on mine.  I only have +5, +12 and GND posts on mine