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Thread: Cree XR-E at 240 lumens?

  1. #41
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    Nope, only two still in the camera, of the thin board with its scribed ink resist covering, and the etched board still in the etchant. I was going to make a set of pics to show the whole method and equipment in a limited set of images, but there's no point now, at least not in this context.

    Just imagine an extremely thin glass fibre board that must be clamped to stop it curling up, sliding hopelessly on hot epoxy till it cures with the board hopelessly out of position, ruining both board and metal backing the moment you try to separate them to redo anything. It's a disaster.

    I learned the hard way why you never hear of anyone doing it that way. Just leave it at that. When I come up with something practical I'll post in this thread again, but not before.

  2. #42
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    Doc - If you haven't thought of this already, how about making the board and backing slightly oversized, apply clamping force only to the dimensions required, then grind off the excess (the outer, un-clamped portion) after curing? This would eliminate the need for extreme precision, and the problem of the clamp surfaces bonding to the work.

    A couple of small wooden blocks could be fashioned to roughly the size you'd like the final result to be. Sangwich (as they say in Noo Yawk) the work between the two blocks, then put the blocks into the clamp. Any mechanism with parallel jaws could provide the force... vise, crescent wrench, etc.

    Speaking of sangwiches, anyone wanna' know of a good, low calorie sangwich?



    A half a sangwich.
    Alas, poor diode. I fried him well.

  3. #43
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    I wish I could, but the problem was the case design, a box profile extrusion with part of one broad side cut out centrally along axis with a bandsaw. The resulting overhanging extensions from the two short sides formed a neat long window that would be filled with a narrow sheet of polycarbon or acrylic, but the access was poor, good enough to get a soldering iron in to work on the board IF it could be fitted accurately, but designing and making a clamp to fit well would be nearly as hard as making the whole lamp, only viable if I was making lots of lamps, and access to grind off surplus without destroying the surface might have needed a CNC machine with carefully chosen milling bits.

    In short, the restrictions of the design were too great, even though it was very simple. It could still work, but only if the board was stiff enough to be easy to remove and replace at will with screw clamping, and if I did that I can forget it, the heatsinking would be so awful that there's no point in trying. Another idea was to use a removable metal plate but the volume was exactly right for the original plan, that extra plate won't fit.

    I haven't come up with an alternative plan yet, I had to let it go to do other things but I'll go back to it when I have an idea and time to try it.

  4. #44
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    I am not finding the Cree Q5 to be crap. I have dropped my Fenix T1 flashlight and the LED did not stop working. Are you referring to their LED as having glue on it's glass?


    Quote Originally Posted by Laser Ben View Post
    In my opinion, Cree products are crap. The 2 engineers who designed the package left Lumileds for Cree when the lighting devision was just getting started. Their product has major flaws and is not a good clean 'white'. The glass lens is stuck on with a small dab of glue at either end and can be knocked out of place very easily. The Luxeon product on the other hand is a much warmer color temperature, has a better package design with better lens, and are brighter. Very soon there will be K2 product out there that actually are rated for 240 lumens.
    Unfortunately I cannot tell you much more about the high power luxeons. I can tell you the emitter will be 4 times as efficient as anything before.

  5. #45
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    Quote Originally Posted by PNjunction View Post
    Well, we wouldn't want that! So for now, I'll have to be content with guessing, and waiting for the eventual announcement. Speaking of guessing... on a hunch, I divided 1200 by 80. Obviously, the answer is 15. The Rebel die is 1mm square, isn't it? 80 Lm @ 350mA. See where I'm going with this?
    Hmm, I'm thinking of a smaller, more efficient version of this:



    http://www.dealextreme.com/details.dx/sku.5766

  6. #46
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    Quote Originally Posted by nanoWatt View Post
    I am not finding the Cree Q5 to be crap. I have dropped my Fenix T1 flashlight and the LED did not stop working. Are you referring to their LED as having glue on it's glass?
    I agree. They aren't crap. And Luxeon Rebels were recalled at some point in the last year. I read of this but still don't know details. New stuff goes bad at times, there's no reason to consistently say that one variant is better than another, it just breeds false hope and false trust. Case in point: Deskstar drives. Old story so I won't say anything except that I've not used anything else for years, and the only one that let me down badly was one I broke myself by dropping it while handling it. Don't beleive the hype, or the unhype.

    The real reason I'm posting in this thread is some unfinished business. I eventually DID finish that LED lamp. The PCB is an older one but it's close enough, I just added two more tracks. I also added a linear regulator, it's not much less efficient than the switchmode one that was in there when I took those photos, and before I broke it. Linear current regulation is easier, and much easier to dim (I added a potentiometer to one end, opposite the BNC power input, on the other end). It's not ideal on a 12V battery, I either need to cheat the regulator into passing most of the sense network's voltage of 1.25V across part of the control circuit instead of in series with the load, or find a variable low dropout regulator. Likely both. But it does work well as it is, and perfectly on a 15V supply.

    It's got Cree X-Lamps in it, and they work fine. The Rebels I have in two Fenix flashlights also works fine. But I wouldn't want to have to hand-solder a Rebel the way I used the X-Lamps in this thing.

    Edit: That last pic is lit by the lamp, and no other source except a bit of dull light from the monitor screen. It's not as bright as a 60W tungsten, but the clarity of vision in a room is similar because there's more shortwave light. The colour is good, once you get used to it, which doesn't take long. It's very efficient, I have a 60W solar panel and two 110 Ah batteries, and that lamp will run constantly even in winter without draining power faster than I can get more, even if the sun only appears once a week. Even a modest computer uses a lot more. Though I'm working toward one that doesn't. Mini-ITX with SD card boot. Should be possible for fully sun-powered use during the six months round the summer solstice.
    Last edited by The_Doctor; 12-19-2008 at 03:11.

  7. #47
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    Looks nice, Doc. Where 'ya been?

  8. #48
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    The reason the rebels were recalled was due to a problem with the YAG of the phosphor on them. It had a pH way too high, about 13, and it was dissolving the epoxy used to secure the die to the chip. This would cause failure in the form of a cracked die or no white output.
    CLICKY!!!

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  9. #49
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    Ok Ben, cool, then the problem was identified and fixed. Great. Weren't any problems with the two I have anyway. My point is, that Cree no doubt also identify problems and fix them too. I've seen you bash Cree at least twice in a way that some people bash Deskstar hard drives. It's bad practise. Few major product lines survive without some kind of trouble. If a major line survives ten years, it's usually safe to assume that the 'trouble' is 1% trouble and 99% web-based blether. I can also add that you're not exactly an impartial observer.

    Steveo, nowhere special.. I put most projects on hold, didn't know what I wanted to do, and needed to stop spending money I no longer had spare for them.

  10. #50
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    Doc,
    Yep, heard that. I've kinda done the same thing. A lot of cash output in this sport..

    Regarding your av-- my wife is a big 'House' fan and I watch the program too now. I just recently found out that he is an English actor putting on an American accent. He does a damn good job of it too. I really thought he was a 'yank' (us) until I heard him talk at an awards show. Kinda unusual and surprising , to me at least.. funny.. somehow.. I dont know why.. just is.. to me.. anyway..

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