Luxeon Star Vs. Emitter

[Ken_McE]

I am working my way into a project where I would have a number of one watt Luxeons mounted in fixed locations. I am considering simply mounting them on sheets of metal or electrical junction boxes and letting that serve as heat sinks. White, green, and cyan are the likely colors. Is there any real difference between the Star and the Emitter? Are they the exact same thing on two different bases? The star is fun to look at, but the emitter seems like it'd be easier to connect to with a plug.

Also, any suggestions on places to shop or avoid shopping for one watt Luxeons?

Thanks!

 

[Erasmus]

An Emitter is actually a part of a Star. You can even remove the Emitter from the Star (explained on this website : http://www.obaq.tv/cpf/?page=Luxeon ) So they are, as you said, the same thing on two different bases. Emitters should be a little less expensive then Stars.

I can give you some shops, but I suppose you won't buy them in Belgium /ubbthreads/images/graemlins/wink.gif

Good luck!

 

[GarageBoy]

Whats the purpose of the star?

 

[3rd_shift]

The stars can be arctic alumina epoxied just like bare emitters can.
Plus they are easier to electrically isolate and to solder.

Note, emitters pulled from stars are not neccessarily the same thing as true bare emitters.
Guess how I know. /ubbthreads/images/graemlins/wink.gif


Star emitters are a pain to pull in usable condition for newbies.
The leads are less flexible and break easier than bare emitters leads do.
Maybe someone will let go of a used Q3 star cheap for you to practice with. /ubbthreads/images/graemlins/icon3.gif

 

[MrMimizu]

If you do get stars you can follow the instructions here to remove the emitter. From what I hear though, skip step two where he carves into the back of the star.

Also I'd suggest that you may want to use some sort of paste like Arctic Silver to help transfer the heat to your steel sheet. If you can clamp them down hard enough it may not be necesary tough. Or you can get some Arctic Alumina expoxy and use that to stick it to the steel.

Isn't the purpose of the star just to give you an easier place to solder to? And probably a bit of heatsinking too.

 

[Ken_McE]

So then the star part is just a heat sink placed under an emitter? Not sure why I'd want to take the emitter off its heat sink. I'm thinking massive heat sinks anyhow, (does a two inch by two inch sheet of #20 copper count as massive???)

MrMimizu, how much are you selling those TWOJs for?(oh, wait, he's in Canada, he'll probably answer in Francs or Euros or something. Hell, maybe I can Babelfish it...)

 

[modamag]

The emitter pulled from a star will have lower Tj compared to a true emitter. Remember reading this from one of the thread.

However, for your application you should stick with the star, it makes life alot easier.

And 2x2 copper sheet is not massive by any means. It depends on how long you keep it on and how much current. Are you planning of DD, LM317, CC5W it?

I have a similar setup with a 2"x3" aluminum plate for my car Lux3T @ 700mA it will cause heating problem when I leave it on for 30 minutes.

Copper is only good for surface heat xfer. I recommend going with aluminum

 

[mrme]

The Star electrically isolates the heatsink, but the emitter does not. If you re running them in series, this could cause problems with emiiters by causing shorts. If it is to be mounted to a vehicle, it could cause even more.

I don't know if using heat sink epoxy that is not electrically conductive will be enough. I wouldn't trust it, but I have never tried.

The star has solder pads, whic will be more forgiving than the leads on the emitter to solder to and won't tear off as easily.

Good luck and be careful what you elecrically connect.

 

[kj]

If you are going to use different colors in one heat sink, I also suggest the stars not emitters. In some color LEDs such as red Luxeon, the slug of the emitter is not electrically neutral and should be isolated. The star does isolate as mrme wrote.

 

[TORCH_BOY]

Stars can also be directly screwed onto a heatsink

 

[n_den]

[ QUOTE ]
ensig said:
The emitter pulled from a star will have lower Tj compared to a true emitter. Remember reading this from one of the thread.

However, for your application you should stick with the star, it makes life alot easier.

And 2x2 copper sheet is not massive by any means. It depends on how long you keep it on and how much current. Are you planning of DD, LM317, CC5W it?

I have a similar setup with a 2"x3" aluminum plate for my car Lux3T @ 700mA it will cause heating problem when I leave it on for 30 minutes.

Copper is only good for surface heat xfer. I recommend going with aluminum

[/ QUOTE ]

while 2" x 2" is not massive it will do. would suggest going with Al. copper will soak up the heat but won't let it go as good.

below is estimate for Luxeon Star on the minimum recommended heatsink size based upon AB05. Junction Temp = 120C, Ambient Temp = 60C(140F), 350mA, 3.42Vf, R Theta = 20 based upon DS23

if you're going to use a flat horizontal heatsink the minimum is: 2.75 sq. in. of exposed surface area.
if your ambient temp is 55C(131F) minimum is: 1.079 sq. in.

on a previous post, i did it for a Luxeon III Star on the minimum recommended heatsink size based upon AB05. Junction Temp = 120C, Ambient Temp = 27C(80.6F), 1000mA, 3.9Vf R Theta = 17 based upon DS46

if you're going to use a flat horizontal heatsink the minimum is: 12 sq. in. of exposed surface area.

if interested send me what star you're using, your highest estimated ambient temp and we'll see what we get.

just a guide. for more info see AB05.

 

[kj]

I'm sorry. I wrote the star would electorically isolate, but it's not correct. Here is an excerpt from DS46 Luxeon III Star datasheet.

"Electrical insulation between neighboring Stars is required – aluminum board is not electrically neutral."

 

[Doug S]

More on the relationship between emitter die and slug can be found in this thread:
die to slug relationship

 

[Ken_McE]

Heat Control

>And 2x2 copper sheet is not massive by any means. It >depends on how long you keep it on and how much current. >Are you planning of DD, LM317, CC5W it?

I'm afraid I don't understand the abreviations. I had the idea that if I gave them a good enough heat sink they wouldn't be able to go into thermal runaway, 'cause they couldn't heat the sink faster than it could cool them. 8-( Because this is a fixed instalation the size and weight of the heatsinks are whatever I like, no limits.

It would be nice, appealingly simple, to just give each one a resistor and a heat sink and wish them well, rather than buying however many hundred dollars worth of current regulating devices. I'm starting to think each one'd need a radiator the size of a dinner plate, or maybe I should mount them in baby food jars full of water... Lets see the little rascals boil that...

I doubt that the building interior will ever get above eighty, rarely ninety degrees farenheight. When the system goes off it will run until the power comes back or the batteries (12 volt, will run a 50 watt load for an hour and a half) die. I can't expect anyone to be there to baby them.

I went out on eBay and picked up some " AAVID THERMALLOY HEATSINKS FOR 1 WATT LUXEON STAR" They look to be aluminum and are not that big, perhaps an inch and a half on a side cubes. Seeing how small they are I thought I could substitute a sheet of roofing copper, or mount them on existing metal equipment, door frames and such, keep my life simple. I'm just not used to the idea of a LED that runs hot. With incandescent bulbs I have experience, a feel for how much heat they will put out and how to install and run them safely. With these Luxeon jobbers I'm pretty much a, uh, (looks around forum, types in sotto voice) a clueless newbie.

I got in some blue 1 watters, they're marked "LXHL-NB98". I Frankenstein rigged one up to a 3 volt DC flashlight and went lurching off to see the world in one watt blue. Spent a fair amount of time putting the light in obscure places and asking myself if a stranger could see and manuver by this light. (in white or green for the actual system though, I got the blues used and cheap, so I can abuse them shamelessly, ledmuseum watch out!) It turns out they have a mild flourescent effect and they are highly irritating to the eyes, as if they have a UV output. Could this be the dental blue???

What I want to do is replace the incandescent bulbs in the emergency lighting system with LEDs. I've been working out tenative plans for lighting heads that are inconspicuous. I don't really like the way otherwise attractive buildings get all cluttered up with functional, but unatractive, mechanical systems.

The bulbs that came with the emergency lights are GE 4044-1 Emergency bulb, 12 volt DC, 12 watt, Par 36(?). They have two bulbs per lighting unit. They put out a nice powerful spotlight type of beam. GE said that the bulb is rated by maximum intensity of the beam (MBCP) in candelas. The MBCP rating is 1100 candelas. I think of one watt luxeons as being 20-30 lumens, but don't know how to compare that to candellas 8-(

My thought with shifting over to LEDs is to reduce power requirements, which should increase the usable life of the batteries in the unit, which slows the replacement cycle,which should lower operating costs. So in the long run the more expensive LEDS would represent a savings on operations. I also would like something a little less dazzling than the 4044-1 when it is in action. They produce a chiaroscuro effect of too bright mixed with too dark.

 

[Ken_McE]

Heat Control

>And 2x2 copper sheet is not massive by any means. It >depends on how long you keep it on and how much current. >Are you planning of DD, LM317, CC5W it?

I'm afraid I don't understand the abreviations. I had the idea that if I gave them a good enough heat sink they wouldn't be able to go into thermal runaway, 'cause they couldn't heat the sink faster than it could cool them. 8-( Because this is a fixed instalation the size and weight of the heatsinks are whatever I like, no limits.

It would be nice, appealingly simple, to just give each one a resistor and a heat sink and wish them well, rather than buying however many hundred dollars worth of current regulating devices. I'm starting to think each one'd need a radiator the size of a dinner plate, or maybe I should mount them in baby food jars full of water... Lets see the little rascals boil that...

I doubt that the building interior will ever get above eighty, rarely ninety degrees farenheight. When the system goes off it will run until the power comes back or the batteries (12 volt, will run a 50 watt load for an hour and a half) die. I can't expect anyone to be there to baby them.

I went out on eBay and picked up some " AAVID THERMALLOY HEATSINKS FOR 1 WATT LUXEON STAR" They look to be aluminum and are not that big, perhaps an inch and a half on a side cubes. Seeing how small they are I thought I could substitute a sheet of roofing copper, or mount them on existing metal equipment, door frames and such, keep my life simple. I'm just not used to the idea of a LED that runs hot. With incandescent bulbs I have experience, a feel for how much heat they will put out and how to install and run them safely. With these Luxeon jobbers I'm pretty much a, uh, (looks around forum, types in sotto voice) a clueless newbie.

I got in some blue 1 watters, they're marked "LXHL-NB98". I Frankenstein rigged one up to a 3 volt DC flashlight and went lurching off to see the world in one watt blue. Spent a fair amount of time putting the light in obscure places and asking myself if a stranger could see and manuver by this light. (in white or green for the actual system though, I got the blues used and cheap, so I can abuse them shamelessly, ledmuseum watch out!) It turns out they have a mild flourescent effect and they are highly irritating to the eyes, as if they have a UV output. Could this be the dental blue???

What I want to do is replace the incandescent bulbs in the emergency lighting system with LEDs. I've been working out tenative plans for lighting heads that are inconspicuous. I don't really like the way otherwise attractive buildings get all cluttered up with functional, but unatractive, mechanical systems.

The bulbs that came with the emergency lights are GE 4044-1 Emergency bulb, 12 volt DC, 12 watt, Par 36(?). They have two bulbs per lighting unit. They put out a nice powerful spotlight type of beam. GE said that the bulb is rated by maximum intensity of the beam (MBCP) in candelas. The MBCP rating is 1100 candelas. I think of one watt luxeons as being 20-30 lumens, but don't know how to compare that to candellas 8-(

My thought with shifting over to LEDs is to reduce power requirements, which should increase the usable life of the batteries in the unit, which slows the replacement cycle,which should lower operating costs. So in the long run the more expensive LEDS would represent a savings on operations. I also would like something a little less dazzling than the 4044-1 when it is in action. They produce a chiaroscuro effect of too bright mixed with too dark.

 

[SemiMan]

The emitter on a star is the same as a standalone emitter. There is no difference in junction to slug temperature. You do need to be very careful mounting emitters though. Not only do you need to use a good thermally conductive adhesive, you need to make sure it is thin so that the thermal conductivity is high. Make it too thick, and you may find a thousand hours out that your LED is not as bright as you would expect.

2"*2" copper is a pretty good heat sink if the air is not stagnant. You need to be careful if you plan to mount emitters directly to steel. Depending on the type of steel, it may be a very poor heat sink resulting in localized heating. In general, stars are easier to use.

 

[cy]

..

 

[cy]

even though most of my lights have emitters. I'm sure leaning twards lights that are designed with stars. way easier to change out. And most importantly if you have a dificult to get bin. like a Wbin or Xbin, you can recycle the star. VS emitters that are epoxy in are there to stay.

The best example is lionheart. don't like the luxeon? star changes out in minutes.