Designing and Building a LED Fixture - Page 3 - The Planted Tank Forum

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post #31 of 400 (permalink) Old 04-01-2009, 03:16 AM
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Wow! I finally found your thread. I dealextreme link did not work. What Cree LEDs are you using? color? wattage?

BTW...I am getting my LEDs over this weekend. So hopefully I will have my fixtures ready for use by Monday and can help you with some practical data.

I could not find in your designs, how high you are planning to mount the LEDs, above the tank. Since you have a deep tank(20"), I think you should calculate the lux on the substrate surface based on the distance. I reflector might also be a good idea for restricting light to be wasted outside the tank, unless you have a hood to mount it in.

Anyways, looks good so far. I am subscribed.
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post #32 of 400 (permalink) Old 04-01-2009, 04:47 AM Thread Starter
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http://www.dealextreme.com/details.dx/sku.2395 is the LED I plan to use, a Q2 bin, less efficient version of the Cree 3 watt LED. I plan to mount this so it is 17" above the substrate, and I extrapolated the data from the nanoreef thread where the poster actually measured PAR intensity at two depths in the water - heights above the sensor. I'm not yet fully committed to this, but having spent as much as I have I am almost certain to go all the way with it. Any PAR data I can get will be extremely useful.

I won't need any secondary lenses since the distribution is pretty good as it is, at that depth. And, yes, it will be in my existing fixture, which will reflect side light back towards the tank.

This has become an all-consuming obsession for me!

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post #33 of 400 (permalink) Old 04-01-2009, 08:14 PM Thread Starter
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I just ordered a couple of fans, http://www.directron.com/sil.html with shipping, they are $25 total, bringing my cost up to $55. If you want to see some testing of fans for noise, check out http://www.directron.com/noise.html. I was shopping for a cheap 12 volt adapter to run the fans when I thought about all of the battery chargers I have collected from cell phones, etc. Great idea! I have a couple that are just the right size and rating. Zero cost for that one.

Today I also got the surface of my "heat sink" sanded and polished as much as I think is needed. I started with 80 grit dry wall sanding paper, which is silicon carbide paper, and it worked very well on aluminum. Then I used 150 and 320 grit to finish sand it. I should have my camera back tonight, so I will plan to take a picture and post it.

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post #34 of 400 (permalink) Old 04-01-2009, 08:21 PM
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Quote:
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I just ordered a couple of fans, http://www.directron.com/sil.html with shipping, they are $25 total, bringing my cost up to $55. If you want to see some testing of fans for noise, check out http://www.directron.com/noise.html. I was shopping for a cheap 12 volt adapter to run the fans when I thought about all of the battery chargers I have collected from cell phones, etc. Great idea! I have a couple that are just the right size and rating. Zero cost for that one.
I got the same fans too but 60mm. 5.99/piece from Fry's and no shipping. For 4 of them for around $26. 2 for each fixture

My drivers can handle the load of the fans too along with the LEDs so I will add them in parallel in the same circuit, so that I don't have to use separate timer for them. And I will have a switch in that leg so that I can switch them off if required without switching off the whole circuit.
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post #35 of 400 (permalink) Old 04-01-2009, 08:47 PM Thread Starter
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I got the same fans too but 60mm. 5.99/piece from Fry's and no shipping. For 4 of them for around $26. 2 for each fixture
Rats!!

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post #36 of 400 (permalink) Old 04-02-2009, 02:59 AM Thread Starter
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Here are a couple of pics of the "heat sink". Notice that it is held together with 4 bolts, with short spacers made of 1/8" x 1/2" aluminum bar between the channels to allow for air flow.

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post #37 of 400 (permalink) Old 04-02-2009, 03:09 AM
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nice! If the dimensions match your tanks length & width you have more than sufficient surface area. While I do mine it is good to see a similar idea taking shape in parallel.

How do you plan to mount it against the reflector?
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post #38 of 400 (permalink) Old 04-02-2009, 04:08 AM Thread Starter
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My light fixture is a DIY wooden one, with an 2 x 55 watt AH Supply bright kit in it. So, I will remove all of that, and use stand-offs to screw this to the top of it. The fans will be above that blowing in from the top, each about a quarter of the way from the end of the heatsink.

I'm currently planning to put the current limiting resistors in a small box mounted on the back of the fixture, with the 48 and 12 volt power adapters in the stand mounted on the wall of the stand, and the DC wires twisted together and running up to the light.

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post #39 of 400 (permalink) Old 04-02-2009, 07:32 PM Thread Starter
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More parts purchased, at Radio Shack:


A DPDT rocker switch - $4.35 (tax included)
A PC board for resistors - $4.00 (tax included)
Roll of hook-up wire - $7.20 (tax included)

Total cost so far: $70.50, and still no LEDs purchased! Of course I had to buy a little soldering iron and some solder, too, but those don't count, being "tools".

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post #40 of 400 (permalink) Old 04-04-2009, 06:02 PM Thread Starter
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I tried to re-learn my soldering skills today, by making the current limiting resistor board. This is definitely a physical skill that needs practice to make it work well, but I think I managed to get all of the resistors soldered in without shorting out any of them.


I have decided to just mount this inside the light fixture against one wall. But, I'm still thinking about how to avoid droplets of moisture from condensation from shorting out the resistors. Some kind of coating seems like the best idea - silicone?

I will have two DC voltage power cables coming in to the light, one 48 volt for the LEDs and one 12 volt for the fans. Managing that neatly was a challenge. But, I found this device in the RadioShack website, so I will use it.


Half will be mounted at the back of the fixture as a socket, and the other half will be the power plug carrying the two voltages from the power converters. These, of course will be spliced to wires from the power converters, and to a 6 foot or so 4 wire cable leading up from under the tank to the fixture.

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post #41 of 400 (permalink) Old 04-04-2009, 08:18 PM Thread Starter
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I just ordered 24 Cree 3 watt LEDs from DealExtreme, for $79.46, http://www.dealextreme.com/details.dx/sku.2395 I'm now well past the point of no return on this project.

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post #42 of 400 (permalink) Old 04-04-2009, 09:37 PM
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A silicone coating would be very messy. I usually spray some clear coat lacquer over any circuit boards that might get condensation/dust/etc. If you need to remove a resistor, just put some nail polish remover on the soldered connections, wipe clean with alcohol, and desolder.

Did this to an LED spotlight over our open-top reef tank, no problems after nearly two years!

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post #43 of 400 (permalink) Old 04-04-2009, 10:27 PM Thread Starter
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A silicone coating would be very messy. I usually spray some clear coat lacquer over any circuit boards that might get condensation/dust/etc. If you need to remove a resistor, just put some nail polish remover on the soldered connections, wipe clean with alcohol, and desolder.

Did this to an LED spotlight over our open-top reef tank, no problems after nearly two years!
That seems like a good plan to me. I assume the lacquer is a good enough insulator for that type of use. And, I doubt that there will be much moisture collecting around the board anyway, given how hot LED heatsinks can get.

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post #44 of 400 (permalink) Old 04-04-2009, 10:38 PM
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I just ordered 24 Cree 3 watt LEDs from DealExtreme, for $79.46, http://www.dealextreme.com/details.dx/sku.2395 I'm now well past the point of no return on this project.
Are these 3w? I see no specs there..


I have these on my tank:
http://www.dealextreme.com/details.dx/sku.2394
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post #45 of 400 (permalink) Old 04-04-2009, 11:14 PM Thread Starter
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Those are the same LED, but different bin designation - meaning that mine are from the group of that part number which have a lower lumen output, the Q2 bin vs the Q5 bin. Mine will be about 87-94 lumen vs about 107-114 for the Q5, at 350 mA current. As I understand it, a given production run of LEDs will have a wide variation in efficiencies, so they isolate them by the range of outputs, and "bin" them with similiar output ones. There are other differences too, in color temperature, for example, that result in a given LED being in a different bin.

Also, the LED "emitter" can be mounted on a "star" circuit board by different distributers, and I think the ones I'm getting are mounted by DealExtreme.

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