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Discussion Starter · #1 ·
I find much pleasure in designing and making things for my planted aquarium, so, even if it isn't essential that I do so I still enjoy doing a DIY LED light. I just got a gifted Coralife Biocube 32 tank. It is designed to be used for a small reef tank, so I find the otherwise great light to be far too blue for me to enjoy using it. Coralife (Aqueon) believes it is ok for freshwater plants if you use the right program that is built-in, but I disagree. (And, I want the thrill of making my own.)

Designing such a light, so that it gives me the intensity I want, with the spectrum I like, is just complicated enough to enjoy doing! Fortunately, Finnex LED lights are enough like SMD LED tape lights for their data to be useful. And, over the past few years I have done enough PAR measuring with that type of LEDs to have some useful data, too. So far, none of the lights I have made with SMD LEDs have given the intensity I designed for, so, for this one I will try to make better use of the data.

From the Finnex data I know that the PAR you get from this type of light is very much affected by how long the light fixture is. For two otherwise identical Finnex lights of different length you get significantly more intensity with the longer one. From the Finnex website:


This is important because the data I have for the SMD LED tape I want to use if from a 24 inch long light, but I need a 16 inch long light, so I need to be able to adjust the data.

to be continued
 

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Discussion Starter · #2 ·
PARvsLengthFinnex.jpg

Finnex LED lights use SMD LEDs, so we can use the data they supply to figure out things like how does the length of a SMD light affect the PAR it produces. This shows that data plotted so it is useful for a LED light of about the size I want to make.

FinnexPARvsDist.jpg

The intensity of the light we get from any light fixture drops with distance from the light. This shows how much the intensity drops for a 20 inch Finnex light, which should be close to how much a 16 inch light will drop in intensity.

I have some data for a SMD light I made that was 24 inches long, measured at 33 inches distance. To determine how much light that fixture would have produced at 17 inches, the distance my new light will be from the substrate, first I need to find the ratio of intensity at about 18 inches distance for the Finnex light at 17 inches vs. what it is at 33 inches. That is about 4 to 1. Next, I need to find the ratio for the light produced by the Finnex lights with a length of 18 inches. That is about 32/50, or .64. So, if I multiply those two ratios I should have a good approximation of how much to adjust my data for my older 24 inch SMD light to make it applicable to the new light I want to make. That is 4 x .64, or 2.6 to 1.

I got about 25 PAR at 33 inches, so that means for a similar light, 16 inches long and 17 inches from the substrate I should get about 25 x 2.6 or 65 PAR.
 

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Discussion Starter · #4 ·
What about SMD degradation over time? Loss of PAR?
I'm hoping to have more than enough light initially, with a dimmer to reduce it as needed. That should extend the time the light will be effective. And, I'm thinking about using a much better heatsink than I used before, so the operating temperature, which is what deteriorates the LEDs, will be lower.
 

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One more parameter, that will affect the light intensity, is the number of rows of LEDs I use. This is some data I got from similar LEDs, where I measured PAR for several different numbers of rows.


If I increase the number of rows from 8 to 10, I should get about 10% more PAR, which would increase the intensity from about 65 to about 70 PAR. Or, if I can use 12 rows, it increases it by about 25%, increasing the PAR from about 65 to about 80. Until I figure out the heatsink configuration I can't decide how many rows I will use.

EDIT: I don't feel confident about my calculated PAR, so I redid it, using my measured PAR at a much closer distance from the light, 22 inches, instead of 33 inches. That calculation gives me about 45 PAR at the substrate, if I use 10 rows of LEDs, or 50 PAR if I use 12 rows of LEDs. That seems more probable to me, and it is just slightly less than I hoped for. Now I feel a lot more confident.
 

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Discussion Starter · #6 ·


I visited Blue Collar Supply to look for something to use for a heat sink. And, I found pieces 8" x 24" of 1/8 inch thick aluminum plates for $8 each. I trimmed it down to 8" x 17 1/2 inches, and used the same screws to hold it in place.
 

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To get 2 more rows of LEDs I added another 1.5 inches of heatsink. Instead of having to struggle with soldering wires to the strips I used clamp on connections. Next step is to attach screw on clips to help hold the LED strips attached to the heatsink.
 

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33 holes drilled, for 33 screw/nuts to hold 33 little clamps in place to help prevent the strips from coming loose from the heatsink. This method for wiring the LED strips is much easier than soldering wires to the tiny solder pads.

Now to connect all of the red wires together, and all of the black wires together, and connect the paralleled wires to the power supply (12 VDC, 5 amp power supply).
 

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It is now fully assembled - almost. The solderless connectors are not as good as they should be. I used 11 of them and 3 of those worked only intermittently until I readjusted them several times. I'm hoping they are stable now. The little plastic clips that hold the tape to the heatsink seem to work well, and they also prevent you from mounting the tapes too close together. But, the continuing problem I have with these tapes is the low quality adhesive tape they use. I sanded the heatsink, washed it at least 3 times with alcohol, and once with soap and water. Still, the tapes don't adhere well with the heatsink. I'm going to use silicone caulk to ensure that the tapes stay where they belong, which shouldn't be necessary, but it does work well.

Tomorrow I apply the silicone caulk, and on Sunday I will probably set it on the tank and measure how much PAR I get.
 

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Discussion Starter · #12 · (Edited)


All of the LED strips are now caulked with GE Silicone clear, to help hold them in place. Applying the caulking on a flat heatsink is as easy as possible. I have 8 strips of white LEDs, and 3 of "horticultural" (deep red with 1/4 blues) LEDs.

EDIT: If anyone wants to try the solderless connectors - beware! They are very tricky to install. No instructions come with the package, so you have to figure it out yourself, or remember to study the Amazon listing for them very closely. I'm having some of them work once then quit working. It's because I didn't install them right. The LED tape end has to go under the contacts on the connectors, not on top of them as seems to be the obvious way to do it. Now I have a struggle to reconnect the correctly, mostly blind, since they work best upside down from how I have them. If I can copy the illustration of how they are supposed to work I will add it here later.

EDIT: After installing those solderless connectors the correct way I have 4 working, a few working intermittently and the rest not working at all. I'm going to remove all of them and just solder the connections, not my favorite job. I suggest not using those connectors at all.
 

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Discussion Starter · #13 ·


You just can't beat solder for connecting small wires! This is so bright it hurts to look at it!
 

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I'm getting 48 PAR at the bottom of the tank! That is pretty close to the 45 PAR I predicted! Math won this contest!
 

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Discussion Starter · #16 ·
I also got a remote dimmer for this type of light, and I experimented a little with it earlier. It does work. Now, I need to put water in my tank, and see how much that changes the light intensity. Then I need to calibrate the dimmer, so I can adjust the intensity to whatever I want, as long as it is less than the maximum the light puts out, and finally, I need to see if the dimmer setting stays the same when a timer turns the lights on - off -on again. Ideally I will be dimming it down to 35-40 PAR, so the LEDs will operate at a lower power to reduce the operating temperature enough to make them maintain their intensity for a few years. Then, if it does deteriorate I can reduce the dimming to regain the intensity. I will probably work on that tomorrow.
 

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Discussion Starter · #17 ·
With the new light.

And, with the original light.


Weird!! With water in the tank the light color looks the same as with the original LED light. Even to my eyes it looks just about as blue.

And, even more weird:


With no water I got 48 PAR! I always knew that the air-water interface focuses the light a little, but I didn't expect it to ever double the intensity!
 

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Discussion Starter · #18 ·
The Dimmer works fine, so far. It dims in steps each time you click the button. In 4 clicks it dropped the PAR from 90+ to about 45 PAR, which is about what I want to use. The 12 VDC power supply for the LEDs was pretty warm, OK, it was hot, with full power on. With it dimmed the power supply doesn't seem to even get warm. I tried disconnecting the lights, waiting several minutes and reconnecting them. They lit up at the dimmed power. If it continues to do that after hours of being off, I will be a happy camper!
 

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Discussion Starter · #19 ·
It is now pretty obvious that the very high PAR reading I got with water in the tank, is a result of light reflected off the glass back into the water. This tank has a semi-bow front, it is curved, so it concentrates the reflected light in the middle of the tank. Now that I have some plants in the tank, the PAR reading is much lower due to the plants blocking some of the light. I had about 40 PAR, after I adjusted the dimmer, with no plants, but that dropped to 25-30 with plants in the tank. So, I adjusted the dimmer again to get back to 40 PAR.
 

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Very interesting! I've notice that even in typical rectangular planted tanks, PAR is often higher near the unobstructed front glass, but not nearly as big a difference as you report in the bare tank.
 
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