DIY LED Pendant Light - Page 2 - The Planted Tank Forum
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post #16 of 165 (permalink) Old 11-21-2013, 12:59 AM
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Hoppy,
Would you you please PM me the links for components? I am just starting to play with LEDs and I like the idea you have here. I would like to light one part of a long tank to a higher level than the rest.
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post #17 of 165 (permalink) Old 11-21-2013, 05:11 AM Thread Starter
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Hoppy,
Would you you please PM me the links for components? I am just starting to play with LEDs and I like the idea you have here. I would like to light one part of a long tank to a higher level than the rest.
PM sent

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post #18 of 165 (permalink) Old 11-21-2013, 09:58 PM Thread Starter
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Now this is weird! (Wired and weird!) I temporarily connected one of my 10 watt LEDs, mounted on its heatsink, to the 10 watt driver for it. Plugged in the power, and it came on. Made an appropriately bright circle of light on the floor, with a well defined boundary, as it should be. So, I lugged everything to my dining area where I set it up to measure PAR and take some photos. Plugged it in and nothing happened. So, I reversed the plug in the wall socket - nothing happened. So, I used an extension cord, with a neon light in the plug telling me the power is there, plugged the LED driver into the extension cord - nothing happened. So, I got my multimeter, and measured the DC voltage at the output of the driver - got a 0 to fluctuating reading. Repeated it a few times - mostly got zero. Unplugged the driver. Just for fun, measured the output voltage for the presumably dead driver - got a few volts, which dropped to zero. What the heck is going on??

I checked the polarity of my connections to the LED several times, and it was correct, for sure. I'm thinking of repeating this with the other driver, but I wish I knew what was going on before I try that.

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post #19 of 165 (permalink) Old 11-22-2013, 08:22 PM Thread Starter
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I figured out what the problem was. The LED was not in good enough contact with the heatsink, so it worked only until it overheated and failed. Today I tried the other LED, removing the aluminum bar extension on the heatsink and mounting the LED to the heatsink using 4 screws instead of two. It worked fine this way, with repeated starts and several minutes of trial running.

So, I set it up to measure the PAR vs distance. I used a steel pipe across the backs of two dining chairs, with the electric cable as the support for the light, with everything taped so it couldn't slip or fall. The results are encouraging and disappointing, both.


At a LED to PAR meter distance of 20 inches I got 21PAR, which is too little, but the light is well contained by the "can" so it gives very little spillover outside the main beam. The intensity within that circle of light drops off about 33% from the center to the edge of the circle - also very good. At other distances:



I got 13 PAR at 25 inches, and about 8 PAR at 33 inches, which is about the distance I want to use it at.

I think my next step will be using more efficient LEDs, probably 2 or 3 whites in each can, possibly without the supplemental colored LEDs. I'm still thinking about that step.

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post #20 of 165 (permalink) Old 11-22-2013, 09:10 PM
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post #21 of 165 (permalink) Old 11-22-2013, 11:57 PM Thread Starter
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I found some 20-30 watt LED rated heatsinks on Ebay, which are the same diameter, but heavier, so I just order a couple of those. Now, I need to decide what LEDs to get - probably 20 watt ones. Depending on the dimensions of the heatsinks I may still be able to include the red and blue low wattage LEDs.

There are some 100 watt, 200 watt, and higher LEDs now available. I suppose those are for welding tungsten pieces together??

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post #22 of 165 (permalink) Old 11-23-2013, 04:46 AM
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Get some thermal paste won't need to screw it in and the heat transfer will be better


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post #23 of 165 (permalink) Old 11-23-2013, 04:47 AM
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Reef central has some led builds with this type if led


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post #24 of 165 (permalink) Old 11-23-2013, 05:49 AM Thread Starter
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Get some thermal paste won't need to screw it in and the heat transfer will be better
I used thermal paste between the LED and the heatsink extension and between that extension and the heatsink. But, one of the tiny screws holding the LED on went in cross threaded and slightly deformed the edge of the LED so it wasn't in good contact in the middle. From now on I will be using 4 screws if I use that type of LED, which I probably will.

It looks like the 20 watt LEDs might have about the right lumen rating to make this work. I'm still debating that with myself though. I would prefer a 30 watt version, but haven't seen one like that on Ebay.

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post #25 of 165 (permalink) Old 11-24-2013, 01:32 AM Thread Starter
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I found several 30 watt LEDs on Ebay and other internet sites. I don't know why I didn't see them before. So, I ordered a couple of them, plus compatible drivers. It now looks like the heatsinks will handle 30 watts only with a fan attached, and it isn't clear from the Ebay listing whether the fan is included or not, although it does say in one place that it is. This project is going to take several weeks, possibly until next year, to be completed. (And, that is if everything goes ok.)

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post #26 of 165 (permalink) Old 11-24-2013, 05:31 PM
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If you modify a nice 100mm case fan (it might be a tight fit since your OD is 4" probably) right above the LED's. You probably will have to settle on a 80mm with a pretty hefy width that has a higher CFM rating.

Nice project though, would go wonderful with a smaller cube
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post #27 of 165 (permalink) Old 11-24-2013, 05:40 PM
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Hi Hoppy,

How about using a box shape insted of cylinder? That way you could get a rectangular beam on the floor, and better suited for our aquariums?

And do you plan to spray paint inside of the can as well?

Thanks and regards.
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post #28 of 165 (permalink) Old 11-24-2013, 07:23 PM
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I like the idea of using the can to blend the colors!
Been using a combination of Cold White and Warm White 10W ebay diodes for a while now. Man do they put out a lot of heat! Had to add more cooling fins to my fixture that I originally planned. I don't even want to imagine the output of the 30W.

The waterproof drivers they sometimes come with mostly react nicely to PWM switching, but some do not!
For the people considering these LEDs with the 44mm lenses sold for them on ebay: The resulting cone of light is fairly narrow with a spread of roughly 22 degrees when using the lens + reflector on a 10W diode.
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post #29 of 165 (permalink) Old 11-24-2013, 11:41 PM Thread Starter
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Hi Hoppy,

How about using a box shape insted of cylinder? That way you could get a rectangular beam on the floor, and better suited for our aquariums?

And do you plan to spray paint inside of the can as well?

Thanks and regards.
The reason for using a round aluminum tube for the housing is the great reflectivity of aluminum, even when not polished. The inside is fairly rough, compared to a mirror, but I have been sanding it off and on, getting it smoother and closer to being polished. No, I won't paint it. A square aluminum tube would work also, but would require some attention to how it is hung, so the square beam of light stays aligned with the sides of the tank. The round one is much easier to work with, for that reason.

I did a lot of surfing looking for suitable fans, and found a Titan "TFD9525H12ZP Kukri" http://www.newegg.com/Product/Produc...82E16835192023 which looks very promising. It has a 90 mm fan, and minimal structure outside so it is largely a round cylinder requiring very little trimming to make it fit the 4" tube. I'm still thinking about how to attach it and be able to easily and neatly hang the assembly. Until I get the heatsinks I won't decide on this.

Haagenize, thanks for the idea!

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post #30 of 165 (permalink) Old 11-24-2013, 11:50 PM
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Have you considered making the can longer above the heatsink?
The chimney effect can often move a great deal of air.
Efficiency being an important consideration, fans can eat up some real power.
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