Luxeon Emitter Questions (more)

[MrAl]

Hello,

I just got my first Luxeon Emitter today. I've worked with
the Star/O before but never with the bare emitter.
Now that i have one, i ended up with a few questions.

First off, the emitter came packaged in a little plastic
dome obviously cut from a reel. Problem is, no markings
whatsoever on the reel, luxeon emitter, nor on the package
that it came in. The only marking on the package is
"LXHL-PW01"
which is the generic number for white LED's made by
them right?
This was suppose to be a "Q" bin which i paid an extra
dollar for, yet there's no proof i got the right one.

Any ideas?

On a side topic, i tested it with my newly arrived
"Slavin4u.com" Li-ion AA rechargeable (which was neat)
but that battery also has no markings whatsoever.
Any ideas?

Take care,
Al

 

[greenLED]

AFAIK bare emitters are not individually stamped with their bin. Aside from trusting your source, I am not sure how to tell whether you have a Q or a "Ñ" bin for that matter. (There is no Ñ bin, just trying to make a point.)

Incidentally, I just saw you asked about using US pennies as heatskins. They work well. They're a pain to file down to size, but that may just be 'cuz I have no power tools to do it.

 

[HarryN]

Exactly correct - that is why Klaus always liked working with the the stars - the bin is marked. In theory, you can measure the bin, but most people do not have an adequate light meter. The Vf of course you can measure with an I/V curve.

One other not so minor point - if you are used to working with stars, you might have some experience with running these at moderate currents without additional heat sinking for short periods. The emitters are MUCH more sensitive to damage if run without at least some kind of heat sink. Also, you will find out just how warm that slug gets if you accidentally touch it.

Many people have a collection of damaged emitters and at least one surprised finger. /ubbthreads/images/graemlins/frown.gif

 

[MrAl]

Hello again,

Hey thanks for the info GreenLED and HarryN.
I'm new to using these bare emitters so every little bit
of information is important to me.

Im prepared (somewhat) to use a heatsink for sure.
I tested up to 70ma without a heatsink already, but
i kept my finger on the back all the while to help
determine operating temperature rise. It did ok, so
i did a few simple measurements and then went up to
about 200ma for 2 seconds. It looks like it's brighter
than my older 'greenish' Lux Star/O which i got quite
a while back now. Also, the color looks almost
pure white (like my now defunct TerraLux) and the light
pattern is very very even.
Another problem came up (he he) and that is...
The beam pattern is a bit TOO wide (geeze, must be 300 degrees!) so i had to order a collimating lens.
I had focused a beam using a small magnifier on the wall
some 12 feet away and got a nice bright spot although
it was small (say 6x6 inches square) at only 70ma.

Any more ideas or info would be appreciated too until i get
thoroughly familiar with these things.

Thanks again,
Al

 

[HarryN]

Hi Mr. Al - It seems really strange to be offering advice to you after studying your post for the last year or so to learn electronics.

The next precautions I would offer would be to carefully watch the soldering temp limit in the data sheet, and of course, note that the LED dome is a lot closer to your soldering iron than on a star.

These points, and my own soldering incompetence have led me to the use of 2 part silver filled epoxy for both the thermal path and the electrical connection.

BTW - the better silver filled epoxies are really tough. I tested 3 brands for adhesion using my 7 year old as the tester. I first cleaned the slug with isopropanal, then bonded and cured at 150 F.

The LEDs survived the following - MANY throws up in the air as far as my son and I could toss it (typ 15 - 20 ft) - landing on concrete. Then, just to make sure, I used the Lux III and heat sink as sort of a "baseball" and threw it straight down onto the concrete driveway - (I used to pitch) so I know it exceeded 60mph from my hand.

I finally took a hammer and chisel and impacted the LEDs sideways - the first to fail was an LED I had "skipped" the clean prior to assembly, but eventually, I did make all of them fail.

Yes - thermal grease is fine - but there is just nothing like silver filled epoxy.

As far as optics - Quite a few people use the reflectors - often IMS 17mm and Fraen optics. McGizmo's area is pretty strong on optics study.

 

[NewBie]

If you bought the emitter from Future, check the packaging/shipping sheet, it lists the bin code there.

 

[MrAl]

Hi again,

HarryH:
Thanks so much for the detailed information there.
especially the point about soldering close to the
plastic dome. I'd hate to touch that with the iron (ouche!)
or even splash it with hot rosin from the core of the
solder. I dont think i'll be testing my led mounting
quite THAT hard (hee hee) but ill definitely put some
thought into buying the silver instead of the aluminum
filled epoxy. I know the heat sinking ability isnt
that much different (in thin layer) but i didnt think
about the actual adhesive quality being different.

NewBie:
Yes i did, and the closest i can find reads exactly:
"My Q :1"
without the quotes.
I also found on the packing slip "Lot" and a number...
...think that's it?

Take care,
Al

 

[NewBie]

The packing slip for example would say:

001
Country Origin: MY
Date Code: 0502
Lot Numbers: UXOH

Yes, the Lot Number is the bin. Details on that are here:
http://www.lumileds.com/pdfs/AB21.PDF

Keep in mind they bin the Luxeons with the --->*DIE*<--- at 25C. It makes a significant difference in color and intensity output vs. a "normal" operating environment.

See this thread for shifts based on temperature:
PWM and Temperature

Useful:
Current dimming vs. PWM dimming

 

[Chop]

Since you are using a 1W luxeon, this probably isn't an issue, but with Lux III emitters, I think it is an issue. On the Lux IIIs, the slug is not electrically neutral. That's been my experience anyway. When mounting the Lux III on a heat that is not anodized, or otherwise electrically isolated, you'll need to isolate the slug from the rest of the light. I use a thin layer of Arctic Alumina epoxy to do this.

Another thing to remember is that there may be a day when you will WANT to remove the emitter from the sink. You really don't want to use something that is too hard to remove. AA epoxy gets more than hard enough, especially if you post cure it.

I've also tried the conductive epoxy. I was just a bit uncomfortable about the amount of resistance in the electrical path due to the epoxy. If you do use the epoxy on the leads going to the emitter, be sure to leave yourself some slack in the wiring to be able to clip some, in the event that you decide or need to replace the emitter.

I would recommend soldering any connections. It isn't hard to do and you only have to touch the leads for a second or two to get a good joint.

 

[MrAl]

Hello again,

Tony:
I do intend to solder the leads very quickly /ubbthreads/images/graemlins/smile.gif

Newbie:
Thanks for the info. I've checked the data sheet on
the bin codes and compared to my emitter. Mine is
"QXOK"
so apparently they sent the correct one /ubbthreads/images/graemlins/smile.gif

NOW, all i have to do is figure out HOW to ORDER a
particular bin (one that's listed as available to that
color) for an emitter.
For example, i'd like to get one (white) like this:
"QXOG"
which would be the same lum bin, same color, but
with lower forward voltage.
Any ideas on how to go about ordering this particular
bin part? This would help a lot.


Thanks much to both of you, and take care,
Al

 

[Chop]

Many here have attempted to order a particular bin. It cannot, with few exceptions, be done. There are some that have been able to get a primo bin because they "know" someone at Future, or another company that gets large quantities of luxeons.

As a general matter, you cannot specify flux, color, AND Vf. I tried to order two reels of a particular bin for a run that I was thinking of doing, and I was told that I had to order at least four reels to be able to specify flux, color, and Vf. Even in that case, I had to give them my choice and an alternate. Of course, I'm a no body and you may have better luck.

 

[SilverFox]

Hello MrAl,

Post deleated...

I misread your question... Need more coffee.

Tom

 

[pbarrette]

Hi all,

@Chop: Wow, two reels and they still wouldn't play ball. That's a lot of cash.

@MrAl,

One thing I always, without fail, do is mount the lux on the heatsink before soldering the leads. You would be surprised by just how much heat is transferred from the die to the leads and vice versa. In fact, it's so much that on my Lux-I's I usually end up soldering the negative lead to the heatsink. Of course, as Chop mentioned, only on white Lux-I's as it has been reasonably determined that this doesn't negatively affect electrical performance. I do recall reading that it does cause problems on non-white/blue/UV Lux-I's. Specifically, I recall problems with the reds.

Either way, mounting the emitter to the sink before soldering the leads is, IMO, the right way to do it.

Also.. There are two leads per side. One is the standard long-lead that is normally used and attached to the star. The other is a much shorter lead, also off center, next to it. These shorter leads are actual leads and can be soldered to in place of, or as well as the long leads. If you decide to clip off the longer leads (as I do for smaller lights), just remember that + is the "closed hole" side and - is the "open hole" side. In that one of the short leads is a bit longer than the other and has a hole, while the other one is shorter and has only half a hole... If you're looking at the LED, you'll know what I mean pretty quickly.

If you need to fit it in an even smaller case... Most of the plastic base can be filed/dremeled/cut thinner radially. If you end up doing this, you will see that the two leads on a given side are actually "fingers" cut from one piece of copper. I had to cut through a lot of the plastic base to make my ArcAAA mod since even the short leads are too long to fit in the Arc head.

Hope this helps,
pb

 

[Anglepoise]

I just received a couple of Lux III emitters.
The seller quoted them as TYOJ. The metal slug in both cases was insulated from both + and - soldering tabs.

 

[john_bud]

A quick way to may heatsinks for emitters is to use a hole saw. I use 7/8" and 3/4" holesaws without the pilot drill to pop out a perfect circle of aluminum. A 2" wide 1/8" thick strap of Al can be bought a larger home and hardware stores.

To keep the hole straight, I use a 2x4 with a predrilled hole of the appropriate size and a second piece of wood as a backer and sandwich the aluminum strap in the middle. The bench vice and a large C clamp holds everything together tight.

Using a drill press or a lather or a mill would be better, but all I have is a drill and a vice! Hey, they come out a LOT nicer than using a hand file!


John Bud

 

[MrAl]

Hello again,


Tony:
As to bin ordering, gee that's a shame. I'd really do well to get
a certain bin Luxeon even if i had to pay twice the price.

SilverFox:
Sounds like me /ubbthreads/images/graemlins/smile.gif The bulk of my food bill is for coffee...that's what
puts the ee's in 'hee hee' (hee hee).

pb:
Hey, thanks for all the interesting info there. I didnt realize that
the leads were distinguishable like that (open hole, etc). That means
i wont have to test future emitters (like i had to do this one) with
a low voltage/resistor (4v/100ohms) to find out the polarity.
I might have to cut the leads down too, im not sure yet, as i'll
probably put this in a small head light too about the size of a
minimag AA.
That's interesting about the plastic base too, if i need to go smaller
i'll have to think about doing that too.

Anglepoise:
Oh so i guess LuxIII emitters are insulated too then?

john_bud:
Hey that sounds like a good idea too.
I can use that idea for drilling out small plastic 'lenses' for
the finished light, because i have to grind one of my lights lens off
because it's glued on (to access the inside of the head for mod'ing).


Thanks again to everyone, and take care for now,
Al

 

[Doug S]

[ QUOTE ]
MrAl said:
Anglepoise:
Oh so i guess LuxIII emitters are insulated too then?


[/ QUOTE ]

Al, No. For the white Lux Is and IIIs, there is an ESD protection diode from the slug to each of the input terminals. The anodes of the two diodes are connected to the slug. Here is a thread that contains everything I know about the electrical relationship between the slug and the internal LED of luxeons.
Lux slug electrical connections

 

[greenLED]

I affix the emitter to the heatsink using Artic Alumina epoxy (it also isolates the Lux's slug). Then I solder. Before I started using flux my soldering was crappy (to say the least). I now use flux every time.

 

[Anglepoise]

With my Fluke set to read continuity, and one probe on the emmiter base and the other on ,first the + and then the -, I got no reading.

Doug. Is this considered isolated? I am confused.

 

[greenlight]

[ QUOTE ]
john_bud said:
A quick way to may heatsinks for emitters is to use a hole saw. I use 7/8" and 3/4" holesaws without the pilot drill to pop out a perfect circle of aluminum. A 2" wide 1/8" thick strap of Al can be bought a larger home and hardware stores.

To keep the hole straight, I use a 2x4 with a predrilled hole of the appropriate size and a second piece of wood as a backer and sandwich the aluminum strap in the middle. The bench vice and a large C clamp holds everything together tight.


[/ QUOTE ]
brilliant! All you need to do is buy a different bit for each project. Just kidding- you'd hate to contract out that job when you can do it at home.