Designing and Building a LED Fixture - Page 27 - The Planted Tank Forum
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post #391 of 400 (permalink) Old 11-29-2011, 04:08 PM
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Originally Posted by silvawispa View Post
I just can't resist, no offence meant!

The answer is there.
Yeah, because we all know there is only one LED type and optics used in the hobby..
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post #392 of 400 (permalink) Old 11-29-2011, 04:38 PM
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Typically about 5/8".

"Hopefully everything doesn't turn out horribly ironic"
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post #393 of 400 (permalink) Old 11-30-2011, 05:38 PM
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Thanks for that.

Anyone have any experience or thoughts on this LDD-H series driver from Mean Well?

I'm looking at building a couple lights that will have 4 different channels of LEDs independently controlled. Each channel would have 4-12 LEDs. I would be using an Arduino board to control these channels via PWM. Any red flags in this spec sheet that I'm overlooking?
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post #394 of 400 (permalink) Old 12-01-2011, 03:15 AM
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Not related to the previous post, but I just had a look at the Cree XPG lifespan documents (they have so far actually completed over 10000 hours of actual testing), and the XPG series holds up quite a lot better than previous ones.. At 55C case and 55C ambient (ambient is actually very important to lifespan), at 1A current at 6000h the LED still produced 100% of output. The L70 life (down to 70% brightness) at 85C/85C/1A is estimated at over 60000 hours.

I don't know about you guys, but I expect that I'll replace my emitters in under 5 years - think about it, in 5 years there will be some REALLY amazing stuff on the market, probably with spectra specifically designed to make plants grow like algae and the colors of our fish melt our eyes.

See page 14
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post #395 of 400 (permalink) Old 02-04-2012, 06:02 PM
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How many / what kind of LED's would be good for a low light 20G High.

I like the idea of having some of that nice ripple effect, but at the same time I don't want stems all growing towards the middle or something.

Would 6 XM-L's on a 10"x10" heatsink work? I'd probably under drive them around 400mA.
Seems like it might be too bright.
It'd have to be passively cooled too I can't stomach the idea of a fan.
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post #396 of 400 (permalink) Old 02-04-2012, 11:04 PM Thread Starter
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A 20 gallon high tank is roughly 24L x 12D x 16H. I don't think a 10" x 10" heatsink would be good for that. Much better would be a 18-20" long heatsink which could be as narrow as 2-3 inches. A piece of extruded aluminum channel would work fine, since you intend to use it at low current.

Using 6 Cree XM-L evenly spaced along that heatsink, say 3 inches apart, running at 400 mAmps should give you about 40 micromols of PAR at the substrate, with the light sitting on top of the tank, with no optics. Raise it about 6 inches and you should get about 30 micromols of PAR, good low light. If you zig-zag the LEDs across the top of the tank so you effectively have two rows, with them spaced about 3.5 inches apart on diagonals - two rows 1.5 inches apart - you should get about 3/4 of that PAR, so you could sit the light right on top of the tank for low light. Then the plants wouldn't grow to the middle quite as much, and the PAR from front to back of the substrate would be more uniform.

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post #397 of 400 (permalink) Old 05-14-2012, 10:42 AM
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hey guys! just want to know if this kind of led fixture can properly light up a 2ft tall tank. i was thinking of putting 8 of these along a 6x2x2ft tank

its a 10 watt led flood light fixture

specs are here

they also have higher wattage bulbs 20watt up.

thanks in advance!
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post #398 of 400 (permalink) Old 03-23-2013, 06:57 AM
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Wow this whole thread is intense and way over my head (I started on the PAR vs Distance thread to attempt to learn how much PAR my LED strip is giving out).... I still have no idea. Can someone help me? I currently have a 20gal high with one of these sitting on top of it: I keep hearing that LEDs aren't strong enough to grow plants, but others have told me this is super high lighting... so I'm gettin' a bit confused! I don't wanna over or undercook my plants. I'd like my PAR to be around 30-40.....
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post #399 of 400 (permalink) Old 03-24-2013, 12:03 AM Thread Starter
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You really have to use a PAR meter to find out how much light you get for that fixture. I notice it can be dimmed, and I suspect you will have to dim it to avoid having too much light for a planted tank.

I'm getting very close to a good design for a conversion of a cheap lux meter to a waterproof PAR meter, so if you want to be on the list for possibly buying one, PM me and I will add your name to my list. It would be way cheaper than buying a commercial PAR meter.

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post #400 of 400 (permalink) Old 01-05-2015, 04:32 PM
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EDIT: After reading the LED FAQ, my questions have been answered.

Last edited by AquaDwell; 01-05-2015 at 05:26 PM. Reason: Read FAQ, questions answered.
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