A DIY LED light for a 45 Gallon Tank - The Planted Tank Forum
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post #1 of 146 (permalink) Old 12-27-2010, 11:57 PM Thread Starter
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A DIY LED light for a 45 Gallon Tank

I'm converting my 45 gallon riparium to a low light, non-CO2 planted tank. This is an opportunity to play with LEDs again

My plan is to use some 3 watt LEDs from Ebay, a Hong Kong seller, half warm white and half bright white. I will use a framework of aluminum channels and angles as the housing/heatsink, and use 36 total LEDs, with a MeanWell ELN 60-48 driver.

Today I bought the aluminum extrusions from my local surplus metals store. I paid $26 for 2 eight foot 2 inch x 1 inch x 1/16 inch channels, and 4 feet of 1" x 1" x 1/16" angle. Oddly enough that store also has some big finned extruded heatsinks too, but those are far from cheap.

I think my total cost for this will be about $150 - $75 for the LEDs, $35 for the driver.

Tomorrow I plan to start working on the frame/heatsink, using blind rivets to hold the parts together.

And, the support method for holding the fixture above the tank will be this one, slightly modified: https://www.plantedtank.net/forums/di...ml#post1192294 It has been laying on my workbench since I made it.

Hoppy
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post #2 of 146 (permalink) Old 12-28-2010, 01:04 AM
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Hoppy, you document things between pretty well to excellently.
If you'd post or PM your PayPal address, I believe some of us would help defray the cost of construction in exchange for every tiny detail of the project. Because we know you're going to make it work.

I'll commit to $10.00.
It will be worth that to avoid re-reading the LED thread again. ;-)

I've read a lot of posts on LED builds but they always omit or seem to omit something. I've not been able to "get" the whole picture. For instance, some talk about drivers, but omit details on weather there is a need for a power supply or if it's a direct 120 V AC to the driver. I had to read a spec sheet to find out Brown on the driver connects to Black, and Blue on the driver connects to White. Sheesh!

One example of what I don't get:
On your post above you mention the MeanWell ELN 60-48 driver and 36 LEDs, but the spec sheet says it can power only 8 to 14 LEDs. ??

Thanks.
post #3 of 146 (permalink) Old 12-28-2010, 02:00 AM Thread Starter
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Quote:
Originally Posted by [email protected] View Post
Hoppy, you document things between pretty well to excellently.
If you'd post or PM your PayPal address, I believe some of us would help defray the cost of construction in exchange for every tiny detail of the project. Because we know you're going to make it work.

I'll commit to $10.00.
It will be worth that to avoid re-reading the LED thread again. ;-)

I've read a lot of posts on LED builds but they always omit or seem to omit something. I've not been able to "get" the whole picture. For instance, some talk about drivers, but omit details on weather there is a need for a power supply or if it's a direct 120 V AC to the driver. I had to read a spec sheet to find out Brown on the driver connects to Black, and Blue on the driver connects to White. Sheesh!

One example of what I don't get:
On your post above you mention the MeanWell ELN 60-48 driver and 36 LEDs, but the spec sheet says it can power only 8 to 14 LEDs. ??

Thanks.
Who is this "Meanwell fellow" who is trying to tell me how to use his product?

That MeanWell driver provides up to 48 volts, at a constant current adjustable between zero and 1.3 amps. 48 volts means it will provide enough oomph for 48/voltage drop of one LED LED's, or for this particular LED, for 48/3.2 to 3.5, or 13 to 15 LEDs in series, providing 1.3 amps through all of them. But, I don't want to drive them at that current. Instead I will drive them at 1/3 of that current or 433 mAmps. To do that I will use three series strings of 12 LEDs in parallel. Wattage will be about 12 x 3.5 x .433 = 18 watts. The rated power for that driver is 62.5 watts. So, if this doesn't work, I'll sue them!

The hardest thing to explain is how I came up with an array of 36 LEDs in 4 rows of 9 LEDs, spaced 3.5 inches apart each way. When I get nice and calm and clear headed, I will try to do that.

P.S. You can't buy me for $10 Now, go read the sticky again.

Hoppy
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post #4 of 146 (permalink) Old 12-28-2010, 05:39 PM Thread Starter
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Here is how I decide how many LEDs at what spacing will give me the PAR I want:

About 6 months ago I bought a few cheap 1 watt LEDs on Ebay, with individual drivers for each one. I reported on that https://www.plantedtank.net/forums/li...led-light.html

Using the PAR data I got I made some graphs:

This one showed how much PAR one LED would give on an off center spot below the LED, at various distances from the LED.

Plotting that data differently gave this:


Since this was for a cheap 1 watt LED, I extrapolated to what a Cree XR-E would give at 425 mAmp. This, from the Cree specifications:


This was the extrapolated plot for the Cree LEDs


I refined it a bit to get this: (As I recall, I calculated what my existing LED light should give, and adjusted the graph until it agreed.)


Continued:

Hoppy
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post #5 of 146 (permalink) Old 12-28-2010, 05:58 PM Thread Starter
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If you use an array of LEDs spaced a given distance apart, both ways, you get nearly uniform PAR over most of the substrate. Such an array would be:


You can see that at a spot under one LED, there are others offset a few inches that can also contribute some PAR. So, you need to determine the PAR contribution for each LED, close enough to contribute any, and add them up for that spot. For example if the LEDs are spaced 3.5 inches apart, 4 LEDs will be offset by 3.5 inches, 4 at 4.9 inches, 4 at 7 inches, 8 at 7.7 inches, etc. The PAR contributions from the ones farther away is small, but with 4 or 8 of them added up, they are significant.

When I did this for the 3.5 inches spacing I got a total of about 50 micromols of PAR. So, I tried it with the rows staggered, and that reduced the PAR down to about 40 micromols. That was about what I want, so I chose 3.5 inches for my spacing.

I have other graphs I use to make this is a little easier, but that's the process.

The array I selected is:

Hoppy
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post #6 of 146 (permalink) Old 12-28-2010, 10:10 PM Thread Starter
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This is the housing/heatsink, not assembled yet, without the holes and notches cut yet. Cutting 1/16" thick aluminum extrusions is extremely easy with a hacksaw. After cutting pieces that are to be the same length, just clamp them together with the ends on one end aligned, then file the other end to even them up.

Hoppy
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post #7 of 146 (permalink) Old 12-29-2010, 02:37 AM
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Quote:
Originally Posted by Hoppy View Post
Who is this "Meanwell fellow" who is trying to tell me how to use his product?

That MeanWell driver provides up to 48 volts, at a constant current adjustable between zero and 1.3 amps. 48 volts means it will provide enough oomph for 48/voltage drop of one LED LED's, or for this particular LED, for 48/3.2 to 3.5, or 13 to 15 LEDs in series, providing 1.3 amps through all of them. But, I don't want to drive them at that current. Instead I will drive them at 1/3 of that current or 433 mAmps. To do that I will use three series strings of 12 LEDs in parallel. Wattage will be about 12 x 3.5 x .433 = 18 watts. The rated power for that driver is 62.5 watts. So, if this doesn't work, I'll sue them!
I believe it might finally be coming together in my head now.
Am I correct that you are going to use three parallel strings, with each string consisting of twelve LEDs in series?

Quote:
The hardest thing to explain is how I came up with an array of 36 LEDs in 4 rows of 9 LEDs, spaced 3.5 inches apart each way. When I get nice and calm and clear headed, I will try to do that.
P.S. You can't buy me for $10 Now, go read the sticky again.
I was actually hoping fifteen of us could buy you a light.
<sigh> I'll re-read the sticky this weekend. It's gotten to be too much for an evening. Maybe if I take notes this time.
I did skip ahead on this thread. It's looking good. Thanks.

A tip for the lazier ones among us. Wrap the aluminum in masking tape to hold your line all the way around the piece and use a jig or sabre saw with a metal cutting blade. Yeah, I'm one of those guys who manages to twist a hack saw blade on every cut. I'm looking at a cast iron one with Vise Grip blade supports for my next one. The UFO grade metal isn't heavy enough for me.
post #8 of 146 (permalink) Old 12-29-2010, 03:12 AM Thread Starter
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Quote:
Originally Posted by [email protected] View Post
I believe it might finally be coming together in my head now.
Am I correct that you are going to use three parallel strings, with each string consisting of twelve LEDs in series?
Yes, that's correct. Oddly enough the manufacturer recommends that the LEDs be interconnected across the strings, like a net with an LED at each crossing of wires. That guarantees that each one gets the same current, but I can't see wasting all of that extra wire.
Quote:
I was actually hoping fifteen of us could buy you a light.
<sigh> I'll re-read the sticky this weekend. It's gotten to be too much for an evening. Maybe if I take notes this time.
I did skip ahead on this thread. It's looking good. Thanks.
That would certainly be nice, but I doubt that there are 15 who would contribute. But, I have a pair of 2 foot lengths of Aluminum channel left, and enough aluminum angle to tie them together, so I could set that up for a light for a 10 gallon tank very easily, if anyone was interested.
Quote:
A tip for the lazier ones among us. Wrap the aluminum in masking tape to hold your line all the way around the piece and use a jig or sabre saw with a metal cutting blade. Yeah, I'm one of those guys who manages to twist a hack saw blade on every cut. I'm looking at a cast iron one with Vise Grip blade supports for my next one. The UFO grade metal isn't heavy enough for me.
I have a reciprocating "demolition saw" that I use when cutting thicker pieces or pieces of steel. But, it is too hard to control for thin aluminum.

Hoppy
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post #9 of 146 (permalink) Old 12-29-2010, 08:03 PM Thread Starter
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The wire passage holes are now drilled in the aluminum channels. The wires to the LEDs need to be hidden from view, so they will all run under the aluminum. It is necessary to drill them before assembling the housing/heatsink because you can't get to the sides of the channels to drill holes once it is assembled.

Hoppy
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post #10 of 146 (permalink) Old 12-31-2010, 04:57 PM Thread Starter
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I ordered 40 LEDs on Ebay, for about $75, and they were shipped a couple of hours after I ordered them! But, then I ordered the Meanwell LED driver, from the cheapest online store, then got a message that it would be shipped in April of this year! I am trying to cancel the order, but everyone at that site is on New Year's vacation, so that has to wait until Monday.

While waiting, I am going to modify this support bracket so it will work with the new light:


I need to change the method of attaching to the light. First step is to take two Tee fittings and stuff the through passage with plumbers epoxy.


I will cut off half of those ends, to leave me with something to convert to attachment fittings.

Hoppy
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post #11 of 146 (permalink) Old 12-31-2010, 06:17 PM
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Sweet we finally get to see your articulated support bracket in all its glory!
Have any examples of the "blind" rivets you used Hoppy?I can't see them

I have a reciprocating "demolition saw" that I use when cutting thicker pieces or pieces of steel. But, it is too hard to control for thin aluminum. Quote~

Nevermind the toxic smoke cloud that arises from cutting aluminum with a rip saw, or zip cut ;(
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post #12 of 146 (permalink) Old 12-31-2010, 07:29 PM Thread Starter
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Nevermind the toxic smoke cloud that arises from cutting aluminum with a rip saw, or zip cut ;(
What is toxic about aluminum and aluminum oxide? I haven't heard this before. It can be dangerous because aluminum in fine particle form can burn pretty easily, and very hot. But, I have used my miter saw, with carbide blade to cut aluminum channels and other thick aluminum extrusions before, with no problems.

Hoppy
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post #13 of 146 (permalink) Old 12-31-2010, 07:49 PM Thread Starter
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These will bolt on to the back of the light housing, and attach it to the support assembly. The electric power wire will thread out the hole in the center of one of them, through the hollow fittings the support is made of, down one of the pipes which will fasten to the wall and be hidden completely.

The reason for the epoxy in the middle is to prevent tightening the bolts from spreading the cut sides of the tee, which would creep under the load, causing the connection to the light to be loose fairly quickly. This way the crushing load is carried by the epoxy.

Hoppy
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post #14 of 146 (permalink) Old 01-01-2011, 02:39 AM
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very simple and creative i like it.
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post #15 of 146 (permalink) Old 01-01-2011, 03:07 AM
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Just get a Milwaukee Band saw and you can cut about anything and it'll work wonders on that thin aluminum
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