LED DIY questions (kinda long)

[wondabread]

I have a few questions about the hardware for DIY LED. This is only about 2 days into design - so, very rough at best.

Background:
I am trying to design a light for a 75g (48" x 18"). I have decided on either 64 or 80 LEDshttp://www.dealextreme.com/details.dx/sku.2394. Thoughts on number? How about optics? I am assuming I might need some considering most of the DIY builds are for small tanks of around 12" depth. At a depth of 22-24" (depending on height of fixture) I wasn't sure on the exact number of LEDs or lenses. Dumb question - the wattage of this LED isn't listed (that I can find). Is this a 3w LED? If it is, is this far too many?

I was planning on 2 5.886"x46" heatsinks. Is this too big? At ~$200, I would love to get something smaller.

I read that you should run the LEDs in series. I am assuming this is only due to the heating characteristics of LEDs and the availability of power supplies' limited outputs. My main confusion comes from the drivers/power supplies to pick from.

I have a lot more reading/learning to do, but it would help tremendously if I could get some direction. For instance, the ELN-60-48 PS...the data sheet only lists an example using an ELN-60-24 with 48 LEDs in series. Does this mean that the ELN-60-48 can run 96 LEDs? This PS runs about $45/each.

I came to 64 or 80 LEDs by trying to match the lumens of my sundial to a comparable number of LEDs. 64 would give me something comparable to my current fixture, but if the PAR of the LED fixture is far greater than that of my current t5 fixture, would 56 LEDs be a better idea?

I currently have 3 different t5 fixtures, all 4 bulbs. One Sundial, one aquaticlife, and one odyssea and after fighting algae vigorously for so long, I rarely use more than 2 of the bulbs. Although, even though I don't use them that often, I like the flexibility of 4 bulbs. I can visually see the difference in the three brands. Obviously the Odyssea is the worst visually, and the aquaticlife is the best - again, just by the eye.

With this LED fixture, I would like to have something that can pump out the light, even if I don't use it to it's full capacity. I like Hoppy's idea of having a switch to go from 350mA to 700mA. I would like to incorporate something like that into this fixture.

So, as of now I have 2 pages of notes, and about 20 webpages open and haven't even scratched the surface of this technology. I am probably going to spend $750 or so on this light in the end. Also, I plan on taking this very slow considering the large investment.

Help is greatly appreciated. Thanks!

[Hoppy]

I found that I had to totally submerse myself into the project when I did this. I was spending most of every day studying LEDs to make sure I understood how they worked, and how to figure out how much light they produce. When you do that you either continue to study and apply what you learn or you slowly lose it. I moved on to other projects, so I would have to start over and relearn the stuff to be of much help.

But, a few thoughts anyway: You don't need optics. One of the problems with LEDs is that you can easily get a spotlight effect, where you have very bright spots of light, surrounded by bigger lesser lighted areas. The higher the tank, the less this is a problem. We don't need nearly the amount of light that reef tanks need, so we can forget optics, and enjoy the blending in of all of the circles of light from individual LEDs to get very uniform light.

Heat sinks don't have to be the heavy, extruded, finned monsters that are usually used. My heatsink made of aluminum channel doesn't even get warm.

[wondabread]

What I have so far now is:

5 ELN-60-48P
60 Cree XR-E Q5
2 or 4 60 or 80mm fans (depending on fixture)
Some aluminum channel

For the PS: The P in the model number denotes it is dimmable with a PWM. Does that mean the PWM is internal to the PSU or do I still need to add more hardware to use it?

The LEDs will be wired in 5 groups of 12, with each group wired in series. Does anyone know if I will need resistors?

Also, can I wire the fans into some of the PSUs? With 12 LEDs in each series that should leave 3.6 volts for each PSU. Can I wire the fans in parallel with 3 of the PSUs? That should be just under 12v (10.8 I think).

Does anyone have anything to add (aside from incidentals like thermal paste, nuts, bolts, and wire)?

Thanks for the reply Hoppy. I can see how this stuff is easily forgotten if not used often.

[FloridaFishGuy]

It seems as if you guys spend way to much on heatsinks for these LED lights. I work for a recycling company that specializes in electronics. We have 1000's of heatsinks. You would just have to pay the scrap aluminum or copper price. Look around your area for places that recycle computers and you will find cheap heatsinks.

[Hoppy]

Originally Posted by FloridaFishGuy

It seems as if you guys spend way to much on heatsinks for these LED lights. I work for a recycling company that specializes in electronics. We have 1000's of heatsinks. You would just have to pay the scrap aluminum or copper price. Look around your area for places that recycle computers and you will find cheap heatsinks.

I looked into this when I made my LED light. It is easy to find surplus heatsinks, but it was very hard to find multiples of identical surplus heat sinks. When the fixture is going to cover the top of the tank, and have 60 different LEDs mounted on heatsinks, it is far easier to use standard aluminum extrusions than it is to try to cobble something together with surplus parts. And, if there is a store comparable to the one near me, that sells surplus extrusions, the price is very reasonable.

[wondabread]

Unfortunately, I know of no store like the one in your thread around me. The $200 heatsink was from heatsinkusa.com. After searching around a little more I found some stuff on ebay that isn't exactly what I wanted for a chunk of cash cheaper that he always stocks.

Even if the whole fixture costs $700, it would be comparable to something that costs $300 or so, not to mention saving on all the bulb replacements and the power savings, it should pay for itself in a few years.

If I can get some of my questions answered, I think I will just have to figure out how to make a box that is permanent and looks semi-pro.

I have been slowly turning my basement into a fishroom, and power is going to be a factor in the near future. I think large scale LED fixtures would do wonders mounted under a shelf and the money saved over the 10 year life builds quickly considering the number of lights I am running now. If I could sell all my t5s, the money could be used to expand and buy more stuff!

That and building something this cool myself makes me feel all warm and fuzzy inside.

[evilc66]

I'm sure a lot of the builds you have seen that have used large heatsinks like the ones from HeatsinUSA have been reef builds. Those use a much higher density of LEDs than what is needed for freshwater, so the heatsink requirements are different. They are still overkill for the most part, but better safe than sorry.

Plate aluminum with angle or c-channel bolted to it is a fair solution for this application.

The number of LEDsto use will depend on what you want your lighting requirements to be. Low to medium light, you could get away with 4" spacing, and use 30 LEDs (10x3). Higher light requirements will need more.

The ELN "P" series drivers need an external circuit to generate the pwm signal. It's not too hard to build, but the "D" model is a 0-10v input, which might be easier for you to use.

I've done a lot of work with LEDs over reefs, but not much over freshwater. I think between Hoppy and myself we should be able to get you on the right track.

[Wasserpest]

Originally Posted by wondabread

power is going to be a factor in the near future. I think large scale LED fixtures would do wonders mounted under a shelf and the money saved over the 10 year life builds quickly considering the number of lights I am running now. If I could sell all my t5s, the money could be used to expand and buy more stuff!

That and building something this cool myself makes me feel all warm and fuzzy inside.

Not to discourage you (I know all about the warm and fuzzy that comes along with building something yourself)... but: Don't expect wonders in terms of energy savings when you go from fluorescents to LEDs. T5 bulbs with a good reflector are very efficient when it comes to lumen/watt.

Just a thought... don't let it keep you from building that hot, I mean cool, LED fixture!

[evilc66]

Not to discourage you, but lumens/watt is a term that doesn't fit LEDs well in this application. Where LEDs really shine (pardon the pun) is in it's PAR production per watt. You don't need to go toe to toe with other light sources in terms of lumens to get the same performance. As a result, you can produce similar if not better results from less wattage on an LED array.

[Wasserpest]

I don't question that.

I just found that some folks (not necessarily aquarists who have done a lot of research) have really high expectations when spending big bux on LED lights. And then comes the harsh reality when they realize that they are not all that cool running as advertised, and that 3W LED doesn't really replace that 20W Halogen light.

There was a huge increase in efficiency back when fluorescent lights replaced incandescent bulbs. I think many expect LEDs to be a similar jump in efficiency and energy savings. They are a big jump in technology, but don't expect your energy bill to be drastically reduced, and pay off the initial investment in a few months.

Don't get me wrong, I love everything LED, and admire your projects. Just like to play devils advocate.

[Harry Muscle]

Originally Posted by Wasserpest

I don't question that.

I just found that some folks (not necessarily aquarists who have done a lot of research) have really high expectations when spending big bux on LED lights. And then comes the harsh reality when they realize that they are not all that cool running as advertised, and that 3W LED doesn't really replace that 20W Halogen light.

There was a huge increase in efficiency back when fluorescent lights replaced incandescent bulbs. I think many expect LEDs to be a similar jump in efficiency and energy savings. They are a big jump in technology, but don't expect your energy bill to be drastically reduced, and pay off the initial investment in a few months.

Don't get me wrong, I love everything LED, and admire your projects. Just like to play devils advocate.

I fully agree, I never understood why people are so fascinated by LEDs. For years people were saying they were so much more efficient, when in reality they've only become more efficient than florescents two or three years ago. I think were the big confusion started is that LEDs from day one were more efficient at creating colored light, since all the energy it uses is converted to which ever colored light you want, with normal light technology, you create white light and then filter out any color you don't want, so you waste quite a bit of energy. That's why LEDs began to be used in traffic lights (cause it's red, yellow, and green), cause it those situations they were the most efficient solution. However, to produce white light, only recently have they become more efficient than fluorescents and only by a very small margin ... small enough that price wise it doesn't make sense to spend money on them ... unless you like the novelty of course. That's my rant for today

Harry

P.S. Of course there are very legit uses for white LEDs, like small spaces, etc. where a fluorescent bulb would be impractical, etc.

[wondabread]

Does anyone thing this should be more spread out for a standard 75g?



It is 48x18 with 60 LEDs. Should I spread them out more?

Any other advice before I start buying parts?

Thanks!

[evilc66]

It can certainly work, but it's an awful lot of light. You could cut back quite a bit on the number of LEDs. As I posted earlier, you could put the LEDs on a 4" spacing and only use 30 LEDs. That was for low-ish light applications. For higher light, just reduce the spacing between the LEDs.

[Hoppy]

First: LEDs do provide equivalent light intensity to PC lights, with lower wattage. I get the same PAR readings with about 40 or less watts of LED light that I get with 55 watts of PC light. Clearly a LED light fixture won't save enough power to pay for the fixure, but it does same power.

It is best to evenly distribute the LEDs across the whole top of the tank, not in two clusters as you show them. My PAR meter measurements show a considerable drop off just a few inches outside the area directly below the LEDs. In fact it takes the light from about 4-5 LEDs to get the intensity you need at any given spot on the substrate, so the outer edges of the LED array provide less light than the inner portions. If I were to build another LED fixture (fat chance!) I would make the heatsink be about 2 inches less length and 2 inches less depth than the tank footprint, and spread the LEDs evenly over that entire area. I found that about 3 inch spacing of the LEDs I used gave the intensity I was looking for, which was in the high end of low light intensity. To get high light intensity I think you would need about 2-2.5 inch spacing, using those LEDs. But, I also run mine at about 400 mA current, so you could probably use the 3 inch spacing if you ran them at 7-800 mA. That would take about 75 LEDs of the type I used.

[wondabread]

I must have missed some replies to this post - I didn't see the post about less leds.

I have read every post on every led build thread I could find on nanoreef and rc.

I would like to be able to be in low mid light range with the ability to turn them up to the high mid light range. I have your schematics for the PWM circuit and have no problem building it.

Less leds means less money spent, which is just fine with me.

Also, like I said before, this is still in the early planning stages. I just learned how to use sketchup yesterday, so there will be more plans to come. I'm looking at building this early next year (after christmas).

Looking at PAR data from the various threads out there (Hoppy - your DIY thread helped a ton) I know I don't need 260 PAR at the top of the tank. However, I would like the ability to hit at least 75 at the bottom, so I don't know where that leaves me. I also realize that there isn't much data out there to make cookie cutter led arrays, so some of this will always be trial and error.

I will have to look through lowe's and hd for angle alumimum, because I have no idea where I would find it otherwise. I wouldn't mind going with it just to save the cash.

I'll work on the design this weekend and see about spreading them out.

Still waiting on the updated pwm circuit plans evil! j/k! You must get a ton of pms asking "how do I..."

Seriously though, I wouldn't mind you doing another group buy for meanwell drivers. I'm sure you don't look forward to that again.

Thanks for the help so far everyone.