5W 'ers, voltage, heatsinks, questions

[IsaacHayes]

5W \'ers, voltage, heatsinks, questions

Got a few simple questions I'm sure most of you could answer off the top of your head.

A) The luxeon "stars" that have that weird shape on them, do they have built in heatsinks? could I fit those into a maglight as is, or is it better to get the bare emiter and put on a heat sink for a smaller size?

B) How much voltage does a 5W need? Like a Cyan? How long would one last on 4 AA's? Oh, and how much are the 5W ones? Are they like $40 each or something?!

C) What is the brightest looking color luxeon? Is it the red-orange? I remember reading somewhere it put out the most light. Or would the actual percevible light be a better thing to go by. So would that be Cyan then?

D) The white 1W's take more voltage than say the red ones, but could I drive one with a 1 transistor or other simple step up circuit diagram and get close the the same battery life of a red one direct driven by 2 D cells?

Thanks for the help!

 

[Rothrandir]

Re: 5W \'ers, voltage, heatsinks, questions

the 5w stars will require heatsinking. the emitters will also. emitters are better because there are less thermal joints and also, there is more mounting flexibility.

i believe 7.5v is good for a 5w. 4aa is underdriven, so it should last quite a while.

brightest color is cyan. the reddish colors aren't available in 5w anyway

yes, you could use a dc/dc boost converter and get similar or better runtimes

 

[IsaacHayes]

Re: 5W \'ers, voltage, heatsinks, questions

Do the 1W luxeon stars need heatsinking? What is the purpose of the "star" pcb or whater the emitor is mounted to? is it a heatsink?

Oh, and how much voltage does a 1W cyan take?

 

[highlandsun]

Re: 5W \'ers, voltage, heatsinks, questions

The star circuit board is supposed to provide sufficient heat sinking by itself for the 1W LEDs.

Can't you just download the data sheets and get this info yourself?

According to the latest version of the DS23 data sheet, all of the colors are 3.42V except red, red-orange, and amber, which are 2.95V typical. And of course, that's only a guideline since it's the current that actually matters.

 

[moses]

Re: 5W \'ers, voltage, heatsinks, questions

IsaacHayes,

I believe the 5W is rated around 6.5 volts? Going by memory. 7.5 volts will be way too much in my opinion, meaning bump well over 5 watts and generate a huge amount of heat. Of course, there are pros here who knows more than I.

Mo

 

[monanza]

Re: 5W \'ers, voltage, heatsinks, questions

An added advantage of the star pcb is that you do not have to apply heat to the LED leads when soldering power input leads. The star provides extra contacts for that purpose which makes it a tad safer for klutzes (that's me).

Cheers.

 

[whiskypapa3]

Re: 5W \'ers, voltage, heatsinks, questions

Isaac

The aluminum backing is not a sufficient heat sink for the LED. Nor is the backing on the Star/C or Star/O. You have to provide some heat path to a large mass of metal, ussualy, in the case of a flashlight, the metal body of the light itself. Typicaly, an AA sized metal lamp driven at 400ma will start to feel warm in about a minute. This will be about 35 - 40 degC, adding up all the thermal resistances (best case approx 60 deg/W or 70-75 degC)the LED junction temp is approaching it's design max of 125 degC.

With a plastic body the LED should be attached to a copper or aluminum slug about the mass of a fifty-cent piece. Even then it should be used for intermittant duty only.

The "funny" shape of the 'Star' is so they can be nested closely on a metal support plate which acts as a heat sink. The square ones are mounted next to each other on metal strips.

The voltage for a cyan Ls can be anything from slightly less than 3 to almost 4 volts. If you buy loose emitters you have to experiment with each one to find what it is. If you buy the mounted ones the bin number will get you in the ballpark.

 

[IsaacHayes]

Re: 5W \'ers, voltage, heatsinks, questions

Ok. The aluminum substrate on the Stars isn't enough alone. I'll just go with the smaller bare emiters and sink them.

In regards to a 5W Cyan lasting on 4AA's. I meant the battery life

I'm trying to build a super-bright spot light type deal into a flashlight a bit bigger than a AA-Mini-Mag. So I'll do Cyan. And 5W if they aren't too much. Else I'll do 1W. Would HD + NX05 be the tightest beam for this size? I can't do 30mm optics

Also, if I drive a 1W Cyan with 4AA's in series, would this "circuit" be better than just a drop resistor?
<pre>
+++...........Q1.......|
Bat | | |
Bat |.ZDiode...|..R1...|
Bat |
Bat |
---..........LS-LED.....
|capcitor|
</pre>
Q1 = transistor (pnp, npn? I forget)

Zdiode = Zenier Diode, reverse voltage breaks down ~3.5v
R1= Suficient value to drop 6v down to 3.5 for the LS.
Capacitor is for a neat fade out effect when shut off.

It's been years since I designed any circuitry (which was HV "devices" driven by 9v's), and I may be all wrong. But if I'm right, if the voltage is higher than 3.5, the zenier diode passes voltage the the transistor, which then stops conducting directly to the LS, and then the voltage contiunes going through the diode through the drop resistor. Then after the battery voltage falls below 3.5 v, the transistor is no longer switched off by the diode, and direct drives the LED giving it more power than if I had used just a single drop resistor. Right?

My 2nd Light will be a 2D Mag, it's bigger so I have more optics choices, but I want a medium-large hotspot for medium range work. So would I need a say LD+30mm optics, or LD+NX05? I want brightest possible light of course still.

highlandsun: Everytime I download a .pdf it's all messed up or crashes. My computer is a total POS right now and I need to build a new one

Also by asking you guys gives me the chance to recieve recomendations for changes to make things better based on everyones experience.

Thanks for the help guys. When I get this stuff made I will def post pics. I also have a few other planned usefull projects with 5mm LED's which I will show the designs of later, a UV combo light being one of them, as well as other non flashlight apps.

 

[Rothrandir]

Re: 5W \'ers, voltage, heatsinks, questions

i don't know much about converters and such...but it isn't a good idea to do dd, you might release the magic smoke!

if you plan on using a d cell *ag, i suggest using the reflector instead of optics. i have found that when using the standard reflector with a lowdome, the beam pattern is very similar to my surefire e2e...a bright corona, with a tight round hotspot.

pics please!

 

[highlandsun]

Re: 5W \'ers, voltage, heatsinks, questions

Originally posted by whiskypapa3:

The aluminum backing is not a sufficient heat sink for the LED. Nor is the backing on the Star/C or Star/O. You have to provide some heat path to a large mass of metal, ussualy, in the case of a flashlight, the metal body of the light itself. Typicaly, an AA sized metal lamp driven at 400ma will start to feel warm in about a minute. This will be about 35 - 40 degC, adding up all the thermal resistances (best case approx 60 deg/W or 70-75 degC)the LED junction temp is approaching it's design max of 125 degC.

With a plastic body the LED should be attached to a copper or aluminum slug about the mass of a fifty-cent piece. Even then it should be used for intermittant duty only.

<font size="2" face="Verdana, Arial">Hm, you're talking about driving it at 400mA when it's only supposed to take 350mA sustained. The red/orange/amber stars have a thermal resistance of 20C/W, and they're only supposed to be 1W parts. Yes, if you overdrive them, you need more heat sinking. Application Brief 11 says that a Star can be driven at the full 350mA without any additional heat sinking, though, and with an ambient temp of 25C the aluminum board will reach 60C.

 

[IsaacHayes]

Re: 5W \'ers, voltage, heatsinks, questions

Rothrandir: Why not? everyone else DD's their stuff.. The circuit would only go to DD mode when the voltage drops down below the LS rated voltage.. so it should be fine right?
Also, I had planned on using optics along with the reflector.. I think that is how ElektroLumens does on their maglights. And I like the beam patterns Wayne always gets.
BTW, how bright is the corona? 50% of the hotspot or even less? And I'll get pics when I got the stuff built. I don't have anything built yet, but I have lots of good ideas. Hopefully soon! (I still have to order a lot of parts)

highlandsun, Well in that case a 1W white star would save a step for the maglight mod (no heatsink required). BUT!, would I still be able to fit the star into a maglight and have it move into the reflector area?

 

[highlandsun]

Re: 5W \'ers, voltage, heatsinks, questions

No, a Star PCB will not fit in the minimag head, unless you do some trimming.

 

[IsaacHayes]

Re: 5W \'ers, voltage, heatsinks, questions

No, I'm talking about 2D.
I'm doing a 1W Cyan in a smaller flashlight, and the white 1W will go in a 2D maglight.

 

[Rothrandir]

Re: 5W \'ers, voltage, heatsinks, questions

yes, dd after a certain point is fine. i myself do only dd mods off of 3cells (and 2 for the reddish colors, though this is much less of an overdrive). i was just conerned that you would attempt to run the luxeon off 6v. while this has been done (crazy bulk comes to mind), it isn't really the safest thing to do, and only a luxeon with a very high vf should be considered when doing it. i blew a luxeon once by pushing 4c's into a 3d body, the luxeon blew after about 30seconds.

carona is ~15% still plenty bright to navigate, but emphasizes the spot. i must say, these are the best beam lights i have...hands down.

 

[IsaacHayes]

Re: 5W \'ers, voltage, heatsinks, questions

No, That is what the circuit I dreamed up should take care of. Running a resistor when the voltage is greater than 3.5, and then running DD when it is below 3.5. Anyone care to comment on it? Will it work or am I crazy?

 

[Hemingray]

Re: 5W \'ers, voltage, heatsinks, questions

My next 5W test project: I took the board from a
recently "killed" 1W Luxeon Star/O, carefully removed the plastic optics assembly, and desoldered and removed the "deceased" LED, replaced it with a 5W RB Luxeon emitter, replaced the optics, and arctic-silvered it to a 2" square heatsink that was removed from an out of service Pentium CPU chip.
Works very well, the heatsink seems sufficient as it doesn't get too warm even after a sustained full power run. It isn't really suitable for mounting into a flashlite, unless I can find one with a larger than usual head (that can accomodate the 2.8" diagonal of the heatsink).

Phase II of this project goes two better:
A 5 Watt Cyan emitter, similarly mounted into a Star/O board and optics. This gets arctic-silvered onto a 1 1/2" square X 1/2 inch thick copper plate, that in turn, gets arctic silvered onto another 2" square Pentium heatsink, which also has a small CPU fan on it.

The mechanical parts are done, just have to insert the Cyan emitter, as time allows.

The predecessor to all this was (and still is) four 1W white Star/Os arctic silvered onto a
2" square ex-pentium heatsink, wired in series, and driven off about 13.2VDC with electronic current limiting set at 375 mA. CPU fan was mounted, not really necessary at nominal power.

/ed B in NH

 

[Hemingray]

Re: 5W \'ers, voltage, heatsinks, questions

OOps, the 1 1/2 inch square copper plate is 1/4 inch thick, not 1/2. Didn't have that thickness in ye olde junque box...

Onward and upward.... More light, is better, but still not enough to ward off the winter blues.

ed B in the frozen wastelands of NH