Critique our idea...

[GSX-1300R]

In my house there is a 4th bedroom and closet that was being renovated a while ago but the project went stale and never got completed. The room has electricity but the closet at this time does not. The closet will have power installed soon with or without this upcoming project.

The electricity that's in the room is through a ceiling fan that doesn't have a light kit installed into it. The light kit that went with it has four spot lights that were not too eye pleasing so they weren't installed.:sick2:

Our thoughts are using 3 Luxeon TFFC K2 Neutral White Stars at 700mA in the closet. The stars will be powered by a Xitanium 120VAC, 12W, 700mA Driver. For the bedroom we were thinking 20 stars. Basically set up like track lighting running off of a dimmable driver (I'm not sure what kind will be used – still looking)

My wife found some precut thermal adhesive tape on the internet. It states that the tape will be able to hold the star to the heat sink surface without anything else like screws. Sounds easy enough. Has anyone ever tried such tape? :thinking:

As far as heat sinking goes… Would we be able to use flat aluminum bar that is 1" wide and 1/16th thick to make a continuous track around the room if the stars were being driven at 700mA? With the ceiling fan pushing air around I would think it would aid in the cooling process.

Dimensions are 6' x 4' walk in closet; the bedroom is 12' x 10'.

Well I need to get back to pulling up carpet and pad because I'm starting the painting later on today.

We're open to suggestions and constructive criticism.

 

[ponygt65]

Do you mind if I ask why you have decided to go with LED's in this application opposed to CFLs?

 

[clg0159]

My wife found some precut thermal adhesive tape on the internet. It states that the tape will be able to hold the star to the heat sink surface without anything else like screws. Sounds easy enough. Has anyone ever tried such tape? :thinking:

I "personally" wouldn't trust tape for a permanent installation, especially at 700ma. You can use Arctic Alumina 2 part thermal epoxy and still eliminate screws.

 

[GSX-1300R]

We wanted to try something different. I have CFLs in every socket inside and outside of the house with the exception of the stove and refrigerator

It's not really a cost saving technique were after since we rarely see an electric bill over $120 per month.

 

[GSX-1300R]

I "personally" wouldn't trust tape for a permanent installation, especially at 700ma. You can use Arctic Alumina 2 part thermal epoxy and still eliminate screws.

That's the stuff I was trying to remember the name to. :laughing: I couldn't remember it to save my life.

I'm not opposed to using screws by no means, but it would streamline the process just a little bit.

 

[Tekno_Cowboy]

I'd like to recommend the SSC High-CRI emitters over the Luxeon emitters. The color rendition should be a good bit better, and they might even be more efficient. (I don't remember off the top of my head what a neutral K2 TFFC rates)

That said, you might want to read this thread.

 

[mahoney]

I have used a couple different brands of heat sink tape successfully. One project is over 2 years old and the tape is still holding. Just be sure to clean the surfaces. Bond failure is usually due to a contamination issue. I have found that any bond failures will usually happen fairly soon so keep an eye on the LEDs for the first few hours of use.

I would go with a wider bar for the heatsink, maybe 2 or 3 inches, but otherwise the idea is OK. If you can use enough LEDs so that the combined forward voltages reached your line voltage, you could do away with the drive circuitry and just use a full wave bridge rectifier and a fuse. This can be dimmed with no problem. Yes, the LEDs will flicker at 120 hz, which may bother some people. The High CRI Seouls are nice, as are 5A Crees and 083 Nichias. But High CRI emitters are not as efficient as the higher color temp ones. And if cost is an issue, consider using older and cheaper emitters, and maybe adding some red LEDs to help improve CRI. On a dollars per lumen basis, the old Lux Vs on sale at ARC are a good deal, and an under-driven Lux V is fairly efficient.

 

[blasterman]

Basically set up like track lighting running off of a dimmable driver

So, basically you plan on putting the alu bars directly on the ceiling facing down, correct?

Buncha suggestions:

- Driven at 700mA and no diffusion LEDs are frikken bright when directly viewed. Without diffusion you'll want to mount them close to the side walls so you aren't staring at them when laying on the bed or watching TV. If the side walls are white, and the LED strips are close to the wall you'll get nice drop down halos and improved ambience.

- I'm not against high CRI, but unless your significant other is into interior design and you have lots of bright art-work in your bedroom standard Crees or K2+TFFC (80'ish CRI) should work fine.

- Alu bar is virtually fool proof given the insane number of projects we've used it for around here. However, I'd feel better if you used 1/8 rather than 1/16. 1" wide should be OK, but you won't be able to cram a dozen 700mA LEDs on one. My math tells me a three foot strip of 1" x 1/8 alu bar would be limited to about four emitters at 700mA. That gives each emitter 18 square inches of radiating area.

- If you're going to mount the bar on the ceiling give it a space to breath because the side opposite a 700mA emitter will get quite warm.

- 10x12 is a fairly small room and it shouldn't take many 150lumen emitters to light it up. Five three foot strips given the parameters above equals 20 LEDs. Doesn't initially seem like much, but that's 3000 lumens, and that's pretty decent for a 10x12 room.

- At 350mA you can use a dab of super glue to affix stars or LEDs to alu bar. However, at 700mA you really want a decent thermal interface. Never used thermal tape because I make my own thermal epoxy with powdered aluminium.

- While neutral white emitters are fine for office space, I still find them a bit sterile for home. What I do is alternate them with warm white LEDs, and this looks really really good. IMHO - better that just using either.

- Running a lot of LEDs with just a bridge rectifier as Mahoney suggested has always intrigued me, but for beginners I'd stick with dedicated LED power supplies.

In a nutshell, what I would do is build a single three foot bar as per what you are thinking, and use this as your prototype to get the kinks worked out. Use it as a base reference in your bedroon to see where you should best mount the lights, and how many you need. Then you can always move that bar to the closet when you go full scale!

 

[GSX-1300R]

:twothumbs Thanks blasterman and others.

I spent a very long time last night looking for 350mA LEDs. I picked up 5 Philips Lumileds (LXML-PWW1-0050) in the warm white color. I'm going to work on the closet first before attempting the larger bedroom.

blasterman, you were correct on the placement of the aluminum bar. I was going to place it on the ceiling adjoining to the wall, so I could get the light to wash down on the walls. Ambient light would be fine for this room since it's going just to be a room to watch movies, play video games or just hang out.

With regards to the aluminum bar can that be painted without any problems? Would the heat from a 350mA LED cause it to flake off? I'm not sure if they make a high temp paint in white… I'm going to see if I can locate some 1" x 1/8th sections of bar at the local home improvement center today.

I was going to use a small DC WW and resisters to power them at first until I get everything the way I wanted prior to getting them hard wired with a LED driver.

 

[LukeA]

Painting is a good idea as it supports emissivity. Matte black is the best, but any color and texture paint will improve emissivity a large amount over bare aluminum. Keeping the coat thin is important as you don't want to insulate the bar against convection. Spray application is the best.

 

[LukeA]

With regards to the aluminum bar can that be painted without any problems? Would the heat from a 350mA LED cause it to flake off? I'm not sure if they make a high temp paint in white… I'm going to see if I can locate some 1" x 1/8th sections of bar at the local home improvement center today.

Stop right there. Order from here. Cut and shipped the metal will still be cheaper than the same thing at Home Depot or Lowe's.

The page I linked to has a listing of Aluminum 6061. Compared to 2024, the thermal conductivity is reduced by a fair amount, so you should consider buying 1/8*1.5 or 1/8*2 bar instead of 1/8*1 if you buy from there.

 

[GSX-1300R]

Stop right there. Order from here. Cut and shipped the metal will still be cheaper than the same thing at Home Depot or Lowe's.

The page I linked to has a listing of Aluminum 6061. Compared to 2024, the thermal conductivity is reduced by a fair amount, so you should consider buying 1/8*1.5 or 1/8*2 bar instead of 1/8*1 if you buy from there.

:huh: I was like what did I do! lol

Thanks LukeA that's a great site that you linked me to. Let me be sure that I'm clear with the dimensions. I can get the...

H: 1/8th inch W: 1 1/2 or 2 inch L: 6 foot

Painting is a good idea as it supports emissivity. Matte black is the best, but any color and texture paint will improve emissivity a large amount over bare aluminum. Keeping the coat thin is important as you don't want to insulate the bar against convection. Spray application is the best.

My first thoughts were when I thinking about painting the bar was taping off the sections of the bar that the LEDs were going to be placed. Should they be bare from LED to bar? Do matte colors differ amonst themselves? I'm not sure about the black for decor purposes but I think a matte brown would be usable.

 

[LukeA]

:huh: I was like what did I do! lol

Thanks LukeA that's a great site that you linked me to. Let me be sure that I'm clear with the dimensions. I can get the...

H: 1/8th inch W: 1 1/2 or 2 inch L: 6 foot

Right. And they can cut it to length for you.

My first thoughts were when I thinking about painting the bar was taping off the sections of the bar that the LEDs were going to be placed. Should they be bare from LED to bar? Do matte colors differ amonst themselves? I'm not sure about the black for decor purposes but I think a matte brown would be usable.

Yes. Mask beneath the stars. Metal to metal contact is best for heat transfer. (but the extension of the concept, metal to air, is NOT better)

The color and texture of the paint are of relatively little consequence. There's a vast improvement going from bare metal in air to white painted metal in air, and there's only a very small improvement going from white painted metal in air to flat black. A thin coat is by far the most important feature of the paint.

 

[GSX-1300R]

Right. And they can cut it to length for you.



Yes. Mask beneath the stars. Metal to metal contact is best for heat transfer. (but the extension of the concept, metal to air, is NOT better)

The color and texture of the paint are of relatively little consequence. There's a vast improvement going from bare metal in air to white painted metal in air, and there's only a very small improvement going from white painted metal in air to flat black. A thin coat is by far the most important feature of the paint.

This is why lovecpf for the helpful people.

Granted I may only know the noobish basics but I have a ton of creativity :nana:

 

[blasterman]

I picked up 5 Philips Lumileds (LXML-PWW1-0050) in the warm white color.

Why the rebels may I ask? Been positive talk about newer Rebels in the LED forum, but aren't the ones you linked the older ones? I get XR-Es from LEDsupply for $5.00, and they are 75lumens / 350mA, and a whole lot easier to straight solder than those tiny rebels:ironic:

Would the heat from a 350mA LED cause it to flake off?

Only if you soldered a couple of my Bridgelux on it :huh:

But no, the bar *should not* get more than warm to the touch if you want proper heat management. A thin coat of Acrylic or Enamel won't hurt things, and plus, you still have the top side that won't be painted. Just remember to space it a bit from the ceiling.

Yes, you want metal/metal contact for the LEDs and it should be masked from paint.

 

[LukeA]

The reduced frustration of LEDs on stars is definitely worth any extra expense.

 

[mahoney]

One advantage of LEDs on stars is that they are on a small heatsink. If the heatsink tape or thermal epoxy bond fails, the LED will last long enough for you to notice the problem, and bond failure is less likely with the surface area of a star. At 750ma, if a bare emitter comes off the heatsink, you notice the problem when the emitter fails.

Another advantage of stars for fixed lighting projects is ease of soldering the wires on, and no risk of pulling the leads off the LED.

I am now putting together my 3rd light driven just off a full wave bridge rectifier, but yes, electronic drivers are more "user friendly". I have used Xitanium drivers and have found them reliable and simple to use. But I don't know if they can be dimmed.

 

[GSX-1300R]

Well I just saw the replies and all I can say is

LOL! Man I thought I was doing good when I saw those rebels at 50lm, 350mA. Yes those XR-Es would be super easy to use compared to my first choice. They even go to 107lm on the cooler colors at 350mA.

I was going to call and cancel my order for those rebels but when I went into my email account to get the order number, I noticed that the order had already been shipped... another So I will use them in another project.

I was going to use the Xitanium drivers as well. I have seen a couple that were dimmable but the cost goes up considerably compared to the non-dimming ones.

Well I'm gonna go shop for some XR-Es... thanks again guys :thumbsup:

 

[Illum]

Our thoughts are using 3 Luxeon TFFC K2 Neutral White Stars at 700mA in the closet. The stars will be powered by a Xitanium 120VAC, 12W, 700mA Driver. For the bedroom we were thinking 20 stars. Basically set up like track lighting running off of a dimmable driver (I'm not sure what kind will be used – still looking)

Given the dimensions of the closet I presume its one of those walk-in variety. Depending on where you mount your LEDs the resulting intensity could either be moderately satisfactory or simply inadequate. Since LEDs are more efficient [lumens/watt] at lower currents, I think you might get more even light if you use 8 LEDs driven at 350ma instead of 700ma. Xitaniums are capable for up to 8 LEDs max for 350ma current output.

Cool white isn't at all preferred for indoor lighting IMO...just way too bright but nothing much under the intensity. Neutral White is okay but if this closet is also going to be used as a dressing room, I'd recommend warm white LEDs for better color rendition [or higher CRI.].
Unfortunately, when it comes to color rendition CRI trades off lumens. And the more LEDs you use the more shadows you will have. Since LEDs radiate its light only in one direction...or rather in angle of steradians instead of emitting light all around like Edison lamps or CFLs, as a result shadows will be more prominent and distinguishable. As a result you might feel slightly dizzy if you use too much LEDs in one area.

As far as I am aware of, MCE's are better used in such places like indoor lighting because the emitters are held closer together, resulting in less shadows and each die is individually addressable for user customized configurations depending on the LED driver used. There are CW, NW, WW tint variations...a little more pricey but there are RGB MCEs as well.

My wife found some precut thermal adhesive tape on the internet. It states that the tape will be able to hold the star to the heat sink surface without anything else like screws. Sounds easy enough. Has anyone ever tried such tape? :thinking:

Sounds like those adhesive tapes that come with RAM heatsinks...I think they provide more thermal impedance than still air, but I have no equipment to validate this claim. I'd recommend Arctic Alumina Thermal epoxy instead. Its a two part mix available in syringe containers, available from 4sevens or [I think] lighthound.

Dimensions are 6' x 4' walk in closet; the bedroom is 12' x 10'.

For your particular bedroom, depending on the ceiling composition sometimes pointing LEDs towards the ceiling [ceiling bounce] evens the light out a bit...but as of now the most cost-effective solution for such a broad area is probably best with CFLs.

As for the heatsinking, it depends on the ambient temperature, metal composition, and installation location. Get yourself a tube of heatsink compound because you'll have to experiment with different heatsinks till you find what's most ideal. Adequate heatsinking should result in warm to the touch and not "hot" even when driven 24/7

When I was building my own fixtures, I've made several experiments. I found that a piece of 1-1/2" aluminum L bracket 4" long and 1/16" thick is sufficient to passively cool one CREE XRE NW star driven at 350ma in an ambient 82F 24/7 with no problems, its can be comfortably held in my hand at anytime.

For drywall/sheet rock I'd keep the temperature as low as possible. If your planning to place heatsinked LEDs on wood furniture, the temperature could be higher...but keep in mind that heat is the ultimate enemy for all semiconductors

 

[LukeA]

I really like 5A tint-bin LEDs (warm white) for fixed lighting. 5A to WC (cool white comparison.