DIY LED for 120P: questions for the experts!

[theblondskeleton]

Here it is. The final stage of my setup is this beast. Here is my plan: please tell me if I have made some glaring errors. I've done my best to digest the mass of info related to the subject. I just hope I'm not missing anything super important.

2 fixtures @ 18” x 6” on 2x 18” MakersLED heat sinks
Hung at 24” above substrate ideally, but flexible

Current for my fixtures: 650-700mA each to maximize LED life

14 Cree XT-E emitters for each fixture
14 in Neutral White (split between each fixture)
14 in Cool White (split between each fixture)

Spaced at about 3” in 2 rows with two in a central position (Should I get wider optics for these two, or consider leaving them open?)

60-degree optics

2 MeanWell ELN-60-48P dimmable Drivers (controller to come, probably an Arduino setup)

Fancy heat sink: expensive - I know. As far as I’m concerned, it’ll be the only heatsink I’ll ever need to buy. With fans included, and the ability to add and remove components, I can upgrade, adjust, and modify to my heart’s content. I have essentially designed my fixture around this heatsink. I have investigated the other options, and I have found what I usually find with DIY projects. If you start with quality components, you will more likely end up with a quality product – unless you’re a DIY wizard. Which I’m not, haha… This has easily replaceable hardware and is designed with flexibility in mind. Very smart. And spendy. But worth it.

To address the cost, I considered how long a DIY LED would last if I were to assemble it out of cheaper parts, and I figured that given my lack of experience with the material I would likely assemble it improperly leading to weak and unattractive construction that would eventually break down. With the components running at around $60 total for a minimal construction, this really became an issue for me. Also, with the thermal epoxy, there isn’t much room for error. I anticipate some degree of error on my part, so I want to minimize the impact on the finished product. Nuts and bolts it is, then.

My major questions are for the experienced LED DIY’ers out there: do these numbers look like I have my ducks in a row? I tried to use Hoppy’s LED PAR calculator to figure out what I needed, but I need a “teacher” to check my work, haha… I never took trig, so I'm at the mercy of higher minds. According to my use of the chart, I got 56 PAR at the substrate with these numbers.

1. Could I go with 12 LEDs per fixture (eliminate the 2 in the middle) and still stay in medium light at 700mA? I’d like to be able to have some range, so I can run these at a low current to maximize life. Too much light, but limited in current and controllability of a dimmer is what I’m looking for.

2. Will this setup be ok for my footprint? I’m concerned about the 18” depth with only two rows so narrowly spaced, but I’m pretty married to the heatsink. At 24” above the substrate, does this adequately solve the issue?

3. At that height, should I go with narrower optics, or will it cause unnecessary spotlighting?

4. I'm assuming I'll need some kind of thermal grease for this installation. Any recommendations?

I think that’s a good start for now. Thanks in advance for the help!

[O2surplus]

What are the dimensions of your tank? Is it 72"x18"x18" ? Is it glass or acrylic?

[xmas_one]

Originally Posted by O2surplus

What are the dimensions of your tank? Is it 72"x18"x18" ? Is it glass or acrylic?

120p is an ADA tank. It's 48x18x18"

[jcgd]

It's glass, 47 1/4 x 17 3/4 x 17 3/4 off the top of my head. It's technically 120cmx45cmx45cm I believe.

Ninga'd

[theblondskeleton]

Ha, thanks for the assist, guys! Yeah, it's approximately 48x18x18. Jcgd is right on the money if you need it exact - 120cmX45cmX45cm. And glass, with 1cm thick high-clarity panes.

[O2surplus]

Originally Posted by xmas_one

120p is an ADA tank. It's 48x18x18"

Aha! The Metric system strikes again! With that knowledge in mind, I think the 2 - 18" heat sinks and the led spacing provided by the OP will provide adequate lighting coverage for the tank.
Be for-warned, The MeanWell drivers that you've selected have a lousy dimming curve. They'll basically turn off the leds at 15 - 20% PWM duty cycle. If you want better dimming performance, check the specs on other makes of drivers or DIY your own using the OnSemi CAT 4101 linear current regulator or the National Semiconductor LM3409 Buck Controller.

[theblondskeleton]

Originally Posted by O2surplus

Aha! The Metric system strikes again! With that knowledge in mind, I think the 2 - 18" heat sinks and the led spacing provided by the OP will provide adequate lighting coverage for the tank.
Be for-warned, The MeanWell drivers that you've selected have a lousy dimming curve. They'll basically turn off the leds at 15 - 20% PWM duty cycle. If you want better dimming performance, check the specs on other makes of drivers or DIY your own using the OnSemi CAT 4101 linear current regulator or the National Semiconductor LM3409 Buck Controller.

Thanks, O2surplus! Your info and experience has been very valuable to this process so far!

Ahh, I remember readings out the dimming curve issue at some point, but I couldn't remember which model that was. I'm not so skilled as to be able to build my own drivers, unfortunately. It would be fun, but I'd be worried about my end product quite frankly.

Any suggestions for drivers that will do the job better without adding too much to my overhead? I've seen some on LEDgroupbuy.com, but they are a touch pricey. Ultimately, it needs to be PWM compatible as I'd like to use an Arduino controller to get the fancy effects and moonlight control.

[theblondskeleton]

So, I'm looking at the Inventronics driver at LEDGroupbuy.com and it looks like the 40W 700mA will work for my needs, but I don't know anything about it. Anyone know about these? What would I need to do to dim these? It mentions a dimming range of 10-100% - is this the same issue O2 Surplus mentioned with the MeanWell drivers? I had really researched the PWM style dimmer, particularly the MeanWell. The Inventronics doesn't have an adjustable current, does it? If not, that's ok I suppose. It runs the 700mA I need. Thanks!

[O2surplus]

I have to admit that I haven't paid much attention to the more recent "off the shelf" LED drivers, with respect to their dimming performance. I have heard that the Inventronics drivers do perform better than their MeanWell counterparts in the dimming department. The lack of linear dimming is only really an issue if you're trying to simulate "Sunrise/ Sunset" or use your main leds as "moonlights". You'll probably need to research the subject a little more to make an informed decision as which led driver to buy.

[theblondskeleton]

Thanks again, O2surplus. Good advice

So after looking at things, it seems that I'm going to go ahead with the Inventronics driver. From what I've seen, there just isn't an off-the-shelf driver that can dim to 1%. I'd need to build one, and I want more knowledge before I did that. The last time I built a circuit board was in high school, so I'm a bit rusty.

I haven't posted anything about the many, many hours I have spent researching this over the last few weeks, but let's just say that there really is a lot to know about this before undertaking it. There are many helpful sites such as RapidLED's very easy to understand how-to guides, Hoppy's richly informative threads on his builds and research, sink and O2surplus's efforts at building highly functional controllers - and the drivers that love them. One may not need to understand the inner workings of a driver, but you certainly need to understand the specs to acquire the correct functionality for your tastes/LEDs.

Unless someone is already working on it, I'm going to compile a thread of helpful links to DIY LED information here and elsewhere on the web. I'll be starting this project tomorrow. Fortunately I'm on break right now, so I have a little time to do this. I have collected a few links already but if anyone has any that they would like to add, PM me so that I can get them all organized. I'm not looking to do anything but gather and organize the info to help others get started. I think a little glossary will be helpful for the real noobs too, so I'll compile some info for that as well. The format I'm looking at will be a FAQ style touchstone for building a fixture. Please PM me good questions as well!

This is an intensely interesting subject with a lot of nuance to be aware of. Help me make it right!

[theblondskeleton]

Here is a link to the beginning of my DIY LED FAQ. For all the experts out there - please help by consolidating our most valuable info! Also, please let me know if there is anything I messed up. I mostly cut and pasted my own notes, and added some comments and links to make it more easy to navigate. Thanks guys!

http://www.plantedtank.net/forums/sh...d.php?t=182365