DIY SMD LED Pendant Light
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Old 02-04-2014, 12:25 AM   #1
Hoppy
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DIY SMD LED Pendant Light


I failed to make a usable light for my tank from high wattage LEDs, so now I'm trying to make one from low wattage SMD LEDs, supplied as self adhesive tapes. I have ordered the LEDS, at least the white ones, from Ebay, and have purchased the aluminum for the heatsink from my local surplus metals dealer, and have started to build the heatsink. Here is the design: (showing a cross section.)



Notice that my LED light calculator program indicates that this will work very well, but that program isn't based on the SMD LEDs, so the result may vary considerably from the calculation. Much more to follow.
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Old 02-04-2014, 12:40 AM   #2
Salmon McCloud
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Are heatsinks even necessary?

Sent from my galaxy note 2
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Old 02-04-2014, 02:45 AM   #3
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All LEDs generate heat because none of them are 100% efficient. A single LED may not need a heat sink to dissipate the heat, but when you put 10 tapes of LEDs side by side, where the LEDs are spaced 2/3 of an inch apart, it would be foolish to assume that no heatsink is needed. These LEDs together will use about 80 watts, so there will be considerable heat involved.

I found the red and green LED tapes for $10 each, but I also got a dimmer for them at $4, so I saved a little.
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Last edited by Hoppy; 02-04-2014 at 02:50 AM.. Reason: More info
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Old 02-04-2014, 03:35 AM   #4
drhemlock2
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i thought you were doing pendants??? did you tell in your pendant log what happened...if not pm me and let me know cause I am building some pendants for my system. I will follow this build for sure..
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Old 02-04-2014, 03:44 AM   #5
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@ 80Watt total, there may be merit in using a perforated board (with " holes ?), or even a metal grate as the top of the box.
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Old 02-04-2014, 05:06 AM   #6
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Why not just use crees from the start? They are fairly cheap on fastTech. http://www.fasttech.com/category/160...s/MTMyPUNyZWU/
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Old 02-04-2014, 06:23 AM   #7
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I thought your pendants were doing good? I just went back and didn't see why you think they failed. Did I not go back far enough?

Do you think any of these options would be good enough for a 28" deep aquarium? I'm still trying to decide how I want to light it and still be cost effective. Or does 28" depth and affordable not coincide with eachother?
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Old 02-04-2014, 03:04 PM   #8
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This will be a pendant, hanging about 36 inches from the substrate, 12 inches above the top of the tank. The 4" diameter, 30 watt pendant I tried did not produce enough PAR at the 36 inch distance, so I dropped the project and sold the parts on the For Sale forum.

The SMD tape will provide about 300 LEDs, for about $15! These are 30 lumen LEDs, not the tiny output ones the original LED tape used. I chose them because I want to try them, they are cheap - very cheap - and my PAR calculation program says they will work. Also, they don't need a LED driver - each LED has a current limiting resistor build in.

Also, I have noted that Finnex LED lights use SMD LEDs, so it is certainly possible to generate high PAR with them.
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Old 02-04-2014, 05:22 PM   #9
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Nice. I'll be tagging along on this one for sure.

Have you ever played around with the GU10 LED bulbs at all?
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Old 02-04-2014, 11:40 PM   #10
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Quote:
Originally Posted by thelub View Post
Nice. I'll be tagging along on this one for sure.

Have you ever played around with the GU10 LED bulbs at all?
No, I looked at those bulbs and decided they wouldn't do what I want, but I don't recall the details. Two reasons the tape mounted LEDs are so cheap are: they are produced as printed circuits, and they are apparently widely used to decorate automobiles. They are also used for store decorations, and other accent room lighting. That makes for a big market, compared to star mounted LEDs, so there are many vendors competing for the business. I'm getting mine from US distributers, one located within a hundred miles from here.
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Old 02-05-2014, 12:03 AM   #11
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I've used a similar LED tape that was probably on the cheap side of manufaturing. It was pretty bright and easy work with, but I've since noticed that I have a few LED's burning out... probably quality control on the off-brand strips and maybe water effecting the circuit (even though it was sold as waterproof and comes encased in some sort of rubber). Since we are on the topic, was recently seeing some interesting circular panels on amazon that could be interesting... anyone look at things like:
Amazon.com: Mudder 12w 2835 SMD LED White Light Round Recessed Ceiling Panel Down Light Lamp: Home Improvement Amazon.com: Mudder 12w 2835 SMD LED White Light Round Recessed Ceiling Panel Down Light Lamp: Home Improvement
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Old 02-05-2014, 03:22 AM   #12
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Quote:
Originally Posted by Hoppy View Post
. . . Two reasons the tape mounted LEDs are so cheap are: they are produced as printed circuits, and they are apparently widely used to decorate automobiles. They are also used for store decorations, and other accent room lighting. That makes for a big market, compared to star mounted LEDs, so there are many vendors competing for the business. I'm getting mine from US distributers, one located within a hundred miles from here.
. . . and, it's an attempt to increase the commercial life of the cheap, low-power LEDs which are only half as efficient as the Cree-types. Besides, some makes suffer badly from sulfuration.

I've given-up on them . In my opinion, the best DIY LED units are made from LEDs rated greater than 1Watt/LED.
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Old 02-05-2014, 07:38 PM   #13
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Here is the mechanical part of the light - a heatsink made from 4 strips of 1/8" x 1 1/2" aluminum.





This is assembled by drilling and tapping holes in the pieces and using #6-32 screws to hold it together, with 4 #8-32 eyebolts for hanging it.
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Old 02-05-2014, 07:42 PM   #14
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Quote:
Originally Posted by Greystoke View Post
. . . and, it's an attempt to increase the commercial life of the cheap, low-power LEDs which are only half as efficient as the Cree-types. Besides, some makes suffer badly from sulfuration.

I've given-up on them . In my opinion, the best DIY LED units are made from LEDs rated greater than 1Watt/LED.
They are cheap enough to experiment with, but I may end up giving up on them too. If the light works for 3 years I will be delighted, since I will want to try something else by then anyway. And, it isn't necessary to make the best DIY LED light, just one that meets our needs.
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Old 02-06-2014, 04:29 AM   #15
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Quote:
Originally Posted by Hoppy View Post
. . . And, it isn't necessary to make the best DIY LED light, just one that meets our needs.
True
(although in my opinion: "best" really means "fit for purpose")
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