DIY LEDs - The write-up

[Lutefisk]

<a href=showthread.php?s=&postid=14873631#post14873631 target=_blank>Originally posted</a> by shikhyung
so if we drive the LED at its max, will it shorten the life of its?

I believe the greatest contributor to shortening the life of LED's is temperature. With the same heatsink driving it at a higher current level will result in higher temperatures and therefore shorter life.

 

[Soundwave]

As far as fiber optics go, as soon as the slightest bit of algae grows on the rods, the point is moot.

 

[Yossarian99]

I noted earlier, that there wasn't much difference in light output between running the LEDs at 750mA vs 1000mA. Because of that, I decided a small sacrifice in output was worth the extended life and reliability of the LEDs.

I used the dimmable 1000mA buckpucks, and used a 5K Ohm trim potentiometer to set the maximum current.

 

[Ziggy692]

This the best thread i have read for the do it your selfers like me good job.

 

[shikhyung]

1-Also, is there a reason why run the blue LED with 700mA, since it has the same If=1000mA like the white one.
2-What is the pitch between the 2 leds, center to center?

thanks.

 

[ReefEnabler]

Question for the Electrical guys,

I am about to wire up my 32vdc power supply. It's a printer supply and has a DC jack that I cannot find a Female Receptacle for (I tried a few from radioshack, no luck), so I will need to cut off the included Jack and use my own connector.

But the wires have no markings on them, how do I tell which wire is + and which is - with a multimeter? Won't it measure 32v regardless of the way the multimeter connects?

Do I have to use some external ground reference to see which is live, or is there a simpler way?

 

[Kdocimo90]

Just a quick question... How many LEDs would you recommend on a 210 gallon 72x28x24? As of now, I have a 14 bulb constellation t-5 fixture, but I cant get over the "shimmer" effect made by MH's and LEDs

 

[kcress]

<a href=showthread.php?s=&postid=14875866#post14875866 target=_blank>Originally posted</a> by Soundwave
By that time, though, I'm sure something else will come along.

Ain't that the truth! Look how far LEDs have come in only 5 years.


shikhyung; There are no "white" LEDs. The white ones are blue ones with a phosphor compound between the blue LED and the light you see. That is why the electrical characteristics between white and blue LEDs are so similar.

 

[lynxvs]

With a multimeter you will read a positive or negative value depending on the connection. Pick one wire and put the ground (Black) lead on it then put the positive lead (red) on the other if you read a positive number the first wire is negative and the second is positive. If you read a negative value you have it backwards.

 

[Yossarian99]

ReefE,

Also make sure the Amp rating on that power supply is high enough for the rating and number of buckpucks you want to power. If you have 8 1A buckpucks like I do and you'll be driving a total of 32V worth of LEDs (add up the Vf's), then the power supply will need to provide at least 8A @ 32V. It would also be wise to add 20% margin to that, as well.

For mine, since I was only running 6 LEDs per string, I did fine with a 24V powers supply. They didn't make a 10A supply, so I got a 12A. Better to be on the high side, of course.

And lynxvs is right - if you put your multimeter on the leads and you get a reading of a negative voltage on the display, then you have the + and - on the wrong way. Simple.

 

[Soundwave]

Gotta love updates!

I took this picture about 10 minutes ago...

Everything is doing very well!

 

[ReefEnabler]

edit... weird... my post an hour ago didnt go through until I posted again!

 

[ReefEnabler]

Soundwave, looks great! looks like colors have improved noticeably since your last updates.


lynxvs and Yossarian99, thanks! I knew it had to be something simple.

My power supply is 32v 2.2a and each supply powers 3 700ma buckpucks, so 2.1a load... only a 0.1a buffer. Not quite 20%... but I am thinking of putting 4500 ohm resistors between the REF and CTRL lines of the Pucks, which would make them operate around 90%, or around 630ma. This would extend the life of my LEDs a bit.

I'm using the 50v 220uf capacitors between the power and the pucks.

Is the 20% rule of thumb incase the current actually drops due to line resistance, or something else (less stress on the parts in the supply?)? Does the capacitor help with that at all?

 

[Yossarian99]

If you're running at tight limits like that, definitely put an ammeter on the supply side of the buckpuck to keep an eye how much you're drawing. It might be worth buying a beefier power supply. Adds to the cost, I know, but I have a feeling that printer PS is going to run very hot on you - and extra heat means less efficiency.

 

[ReefEnabler]

I havent been able to find anything larger in 32v output... unless you get into this kind of territory:

http://www.globaltestsupply.com/test_equipment/BK_Precision_1672_Triple_Output_DC_Power_Supply.cfm

I didnt realize 32v was so much harder to come by than 24v when I planned this out....

Another printer supply does 2.5a but thats not much over 2.2.
http://www.yottadeals.com/ProductDetails.asp?ProductCode=YD-HP-0957-2093

best solution is probably just use more supplies and run less pucks on them.

 

[DheereCrossing]

That project I mentioned earlier about a hot wall wart is fixed. The p/s was 300ma and he got a 700ma and if fixed the issue and made the LEDs much brighter. Would going with an even larger supply, like 1000ma cause a problem? Where does any extra power go?

 

[stugray]

Here is a good place for power supplies:

http://www.mpja.com/products.asp?dept=465&main=1

http://www.mpja.com/products.asp?dept=23&main=1

The second link even has 48V 3A for under $100

Stu

 

[shikhyung]

NOTE* - I used 700mA drivers on the BLUE and 1000mA drivers on the WHITE.
I refered to sounwave note.
what is the spacing between the LEDs, I plan to do on my 24x18x20? should a 3 rows x 6 leds with 2" apart from center to center is applicable?

 

[ReefEnabler]

<a href=showthread.php?s=&postid=14881717#post14881717 target=_blank>Originally posted</a> by stugray
Here is a good place for power supplies:

http://www.mpja.com/products.asp?dept=465&main=1

http://www.mpja.com/products.asp?dept=23&main=1

The second link even has 48V 3A for under $100

Stu

Stu, the pucks all say maximum input of 32v... is there some way to use a higher voltage with them?

 

[ReefEnabler]

Found 5 of these 32v 12a CNC router supplies, similar to what soundwave used only beefier.

http://cgi.ebay.com/ws/eBayISAPI.dl...Category=71394&_trkparms=algo=LVI&its=I&otn=2

99 bucks... at that price I'd have to use the single supply to power all 6 of my pucks, which means I'd lose the ability to control blue/whites independently with my profilux power bar. But I could use a separate high voltage relay.

Could wire this to a plug that goes into the Profilux supply and then connect the Blue LED buckpucks across the relay contacts..
http://www.grainger.com/Grainger/items/1A491

That thing looks like it could run off 120v for control and then the relay could handle 32v ~2a ok?