36" x 8.46" CREE XR-E Fixture build

[akaimal]

I am planning to replace one 400 W MH Radium fixture with LEDS on my 240G SPS REEF tank. After doing some cost analysis on building one, found reefledlights.com to be reasonable. Hoping to order the following items from them.



Total cost: $580

Site: https://www.reefledlights.com/

Parts:

24 CREE XR-E Q5 Cool White 3W LED On Star with 60 degree lens

24 CREE XR-E Royal Blue 3W LED On Star with 60 degree lens

36" x 8.46" Heatsink

Arctic Alumina Thermal Adhesive

2 Mean Well PLN-100-48 drivers

I am hoping to use one driver to drive 24 LEDs (2 strings of 12 LEDS in parallel) at 1.8MA, based on the following wiring diagram:

<img>http://www.reefledlights.com/wp-content/uploads/2010/06/Led-Lights-Chart-2-lines-12.jpg</img>


Let me know if I am missing something. Thanks!

[TheFishMan65]

That is not enough light for a 240 IMHO.

You'll probably want fuses or resistors in there for safety.

[akaimal]

Thanks FishMan. I am not sure about how to exactly calculate the resistor needed for my circuit. Could some one point me to some information on how to calculate this?
Do I add a resistor to each of the series threads so that the current that flows through it gets limited to the maximum allowed limit for the series?
Thanks!

[westmoorenerd]

XR-Es are not designed to run continually over 1mA, 1.8mA would blow your LEDs.

[tahiriqbal]

XR-Es are not designed to run continually over 1mA, 1.8mA would blow your LEDs.

Its not a (mA)..... Its Amp sir so 1Amp or 1.8Amp. XR-E would run just fine @ 1Amp but would blow up with a nice blink if ran @ 1.8Amp.

[westmoorenerd]

Lol, true true...sorry it's late here and I'm watching TV at the same time.

[TheFishMan65]

Yes, but he plans to run 2 strings in parallel. So each will get .9 amps or 900ma. That was why I suggested fuses or resistors.

akaimal, The PLN drivers have both current and voltage adjustment on the inside. So you don't have to have the fuses or resistors. I would probably uses fuses.

From my understanding to configure the PLN first turn down the internal current adjustment all the way. Attach your LEDs and apply power. Measure the current coming out and turn up the current until you get to the point you want (two meters may help so you can measure both string and make sure they are close to the same). Turn if off and switch to voltage. Measure the voltage coming out of the PLN. Turn down the interanl voltage adjustment. At first it won't move because the current is the limiting factor, but eventually the voltage should start to drop. No turn it up to just the point where the voltage is back to what you originally read.

No if you loose a string the PLN can't raise the voltage in order to increase the current so the current in the other string should be the same.

This is how I understand these work, but I have not tried it. I personally would still have fuses a cheap protection in case something goes wrong. Can a PLN stop regulating? How stable are those internal setting? etc.

[mtcs]

If I may, since you would need lots of leds, http://www.cutter.com.au/products.php?cat=Cree+XPG sells a 4x4cm PCB with 7 XPG leds on it for a reasonable price (U$ 6,5 per led) . So it would be lot less soldering for you.

I think reefledlights are a little expensive...

[TheFishMan65]

Less soldering, but you may get spotlighting. The XR-E IMHO have enough light it just the issue of spacing them to avoid spotlighting. With the 7-ups you are going to have a lot of light in one place. I haven't seen a tank so I am not sure how big a deal it is.

[mtcs]

The way my XPG LED flashlight brights without the reflector I can say that it is veery disperse, i will try to photograph it. If someone wants to put the lighting pending high up in the sky. They sells optics in various angles...

here it goes

http://img130.imageshack.us/img130/7091/foto0092v.jpg

The beam would be wider if the led wasn't in the flashlight ( I removed the reflector). My finger is also in the way, hehe.

I have a r2 XR-E LED here somewhere, but I cant find it and I would have dome trouble to lit it. But from what I remember the beam if much more focused. The data sheet should show how much focused.

ah... the picture is not so good, but I hope I could help...