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Thread: My "Light Box" or poor man's Integrating Sphere ...

  1. #1
    *Flashaholic* wquiles's Avatar
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    Default My "Light Box" or poor man's Integrating Sphere ... with fan cooled HS!

    The most amazing thing about this project is that I have been thinking about it since last summer. It was not until tonight that I got it running for it's intended, main purpose, so basically, on and off, I have been working on this project for over 6 months !!!

    The main goal was to find a way to test LED's before I put them in lights. We all know that the LED's have certain bins of tint, voltage, and intensity, so many times we modders finish a light only to find too late that the LED was not all that awesome

    Although I am not claiming that I met all of my design goals, this is what I was trying to do:
    1) This Light Box (LB from now on) was conceived as my own way to test LED's against each other in a very repeatable way.
    2) The LB was designed to be inmune to outside light so that I can run these tests anywhere in my house, day or night.
    3) The LB had to use a power source that could be changed, so that if keeping the LED the same, I could test which driver and/or battery source would work best.
    4) The LED had to be thermally stable, for at least the 30-60 seconds of a test run. The idea of course is that the testing would not damage/kill the LED under test.
    5) Although soldering wires to a STAR would have been fairly easy, I wanted this setup to also work with bare emiters.
    6) The LED "station" should be removable so that I could also test flashlights, even if not in the most perfect way (the LB is affected by the reflector/lens).
    7) I could use almost any light meter. I have two different ones, so I made sure I would be able to test with both.
    8) The LB must be fairly heavy/stable, and capable of working for years and years.
    9) The LB must be movable/portable so that I could take to events and share with other flashaholics.

    So here are some construction steps. Everything is glued with biscuits for long term stability/strenght:








    All internal panels were sanded in between coats of white paint (4 layers), and then 2 layers of clear acrilic. The surface is not like a mirror, but it is very flat and even. Here is the outside, removable "house" prior to being glued permanently:


    Aftern being glued, I used some wood dowels to make sure that the house would line up exactly in the same place every time it was used. That inner piece helps reflect more of the light and prevents ANY light from hiting the light meter directly. This LB only measures reflected light:


    I made one "port hole" on the side (which when covered prevents any light from coming in) which allows me to see the LED or flashlight being tested, and allows me to see the tint of the LED which I can even photograph for comparing to other LED's later on:







    Here is not-completed-yet way in which I am bringing external power to the LED:



    Here is the completed setup. Yes, that is a modamag copper heat sink that has been "modified" to work in the LB. I took copper wires and trimmed them into the hole and used artic alumina to create a "fairly" even surface for the LED:





    So when you are ready to test an LED, use a little thermal grease:





    And then the two holders apply spring presure right onto the legs of the emiter to make electrical contact. For bare emiters, I first put a little grease on a generic star that I got some bare emiters I purchased earlier, and then put a little thermal grease between the star and the emiter. The spring presure keeps everything with the right thermal path, so I can test both stars and emiters on this setup:



    A little dark since I am underdriving this LED, but here is the working setup:









    and with the house in place sealing outside light:





    The mating surfaces between the base and the house have thin foam pieces which seal the light when compressed by the short elastic bands:



    Same setup above with the port open and with overhead lights:





    and with the lights in the garage off:



    So does this qualify me as a flashaholic or what !!!

    Will
    Last edited by wquiles; 06-16-2006 at 08:12 PM.
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  2. #2
    *Flashaholic* CLHC's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by wquiles
    So does this qualify me as a flashaholic or what! ! !
    I would say so! Look at that detailed work you put into it! Way to go Will!
    LUX'Ottica

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    Flashaholic* LEDcandle's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Looks like a great setup and thanks for the detailed pictorial article!!!
    You aren't just a flashaholic, you're a flashaholic*!

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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    wquiles

    Great job!
    Now we look forward to some data-how do you plan to calibrate it?
    Do your light meters have a linear response so a single measurement of a known source will do the trick? I am still coming up with peak lux off my light meter as my only way of assessing differnet LEDs so your setup looks fantastic!
    Kind Regards

    David

  5. #5
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Thank you guys

    The idea is to try to find an LED that has been tested already, preferably on a real IS, so that I can calibrate my setup. I already got a 750mA and a 1000mA constant current Downboy converters ready, so I can test one LED against another in a repeatable and controlled fashion. But without a "calibrated" LED with a known lumen output, all I can measure are relative numbers/units, like LBU - "Light Box Units"

    I have many LED projects that I have not finished becuase I have been waiting for this LB to be finished. I will probably start going through my "collection" of LED's and start testing them for intensity, vf, and tint shortly. I will try to setup my camera so that I can take photos of the LED's through the port hole so that I can go back later and remember how they looked like.

    I plan to keep a small database of my tested LED's so that I can pick/choose LED's for particular setups. For example, my current idea is to use the higher lumen LED's for single LED lights and the lower lumen LED's should be perfect for multi-LED lights (like on a M*g platform) where I can pick LED's of similar output and/or tint.

    I can also use this setup to test for lumen vs. vf, which could be really exciting now that we have more "W" intensity, "S" vf 5W LED's - you could really hand pick a high lumen, very low vf 5W for that "special" light

    Having this setup really opens many possibilities for LED projects

    Will
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    wquiles

    Yes I know what you mean- for that time when you have a great host and want the best "sub-bin" LED for a really special torch. Good luck!
    Kind Regards

    David

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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Hello Will,

    I believe you are next in line to check out the CPF Light Meter Benchmarking Lights. You can look through that thread to see what Don came up with for them in his integrating sphere, and at the end of passing the lights around, we will be shipping them of to a certified laboratory to get the official word on those lights.

    That should give you a good comparison of several different colors to start things off.

    Tom
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  9. #9
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Yes, in fact, that is why I got my but in gear and finished the LB. With these test lights coming my way, this would be an excellent way to "calibrate" my LB to several known flashlights

    I will test all lights with my two meters and I will keep track of my results in my own "database"

    Will
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  10. #10
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    I just finished recording the lights used for the light meter experiement which will later be sent to be used in a real IS. This is at least some data that I will use to more-or-less know what to expect of the light box when testing flashlights, even if the primary design goal was to test LED's

    The first two sets of numbers were recorded using the reference lights in the usual manner, recording light directly aimed at the meters. The last two repeat the same tests, but using the meters to record reflected light inside of the Light Box.

    Test #1 - Meterman LM631 Light Meter, Serial 0503014
    Recorded on 3/21. Temperature 61F

    Light=Measurement (Lux@1Meter) #1/#2/#3=Average
    A2=2200/2260/2230=Ave=2230
    A1 White LED=836/850/854=Ave=847
    A1 Green LED=1279/1298/1286=Ave=1288
    A1 Red LED=2370/2340/2420=Ave=2377
    A1 Blue LED=823/817/820=Ave=820


    Test #2 - Lutron LX-102, Serial Q030770
    Recorded on 3/23. Temperature 53F

    Light=Measurement (Lux@1Meter) #1/#2/#3=Average
    A2=2520/2540/2490=Ave=2517
    A1 White LED=1211/1147/1193=Ave=1184
    A1 Green LED=2670/2650/2670=Ave=2663
    A1 Red LED=1580/1600/1570=Ave=1583
    A1 Blue LED=760/750/750=Ave=753


    Test #3 - wquiles' "Light Box", Serial 001
    Light meter used = Meterman LM631 Light Meter, Serial 0503014
    Recorded on 3/23. Temperature 76F
    Note that the Light Box measures reflected light only
    Light=Measurement (in LBU's, or Light Box Units) #1/#2/#3=Average
    A2=560/570/572=Ave=567
    A1 White LED=298/289/293=Ave=293
    A1 Green LED=230/233/234=Ave=232
    A1 Red LED=630/630/627=Ave=629
    A1 Blue LED=175/174/177=Ave=175


    Test #4 - wquiles' "Light Box", Serial 001
    Light meter used = Lutron LX-102, Serial Q030770
    Recorded on 3/23. Temperature 76F
    Note that the Light Box measures reflected light only
    Light=Measurement (in LBU's, or Light Box Units) #1/#2/#3=Average
    A2=570/567/578=Ave=572
    A1 White LED=395/398/398=Ave=397
    A1 Green LED=427/426/425=Ave=426
    A1 Red LED=353/351/351=Ave=352
    A1 Blue LED=39/39/38=Ave=39 => Note value is way too low. I did several times, but always got this range. Don't know why

    I hope to test some LED's soon

    Will
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    Flashaholic* chevrofreak's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    look ma, it's an integrating birdhouse!


    I look forward to your readings on other lights as I am preparing to build an integrating "oddly shaped object" of my own before long

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    *Flashaholic* Darell's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Awesome! I've gotta say, I'm most impressed!
    - Darell, the EVnut
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    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by chevrofreak
    look ma, it's an integrating birdhouse!

    I look forward to your readings on other lights as I am preparing to build an integrating "oddly shaped object" of my own before long
    Yes, a birdhouse is a more appropriate way to describe this contraption



    Quote Originally Posted by Darell
    Awesome! I've gotta say, I'm most impressed!
    Thanks

    Will
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Like your integrating bird house. Complete with lighting!! It would be a little small for me though. Of course I can always chew a little larger doorway, and let my tail poke out of the hole...
    Last edited by Macaw; 03-25-2006 at 11:14 AM.
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  15. #15
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Yep, I think this one would be a tad too small for ya ...

    Will
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    *Retired* NewBie's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by wquiles
    A1 Blue LED=39/39/38=Ave=39 => Note value is way too low. I did several times, but always got this range. Don't know why

    Will

    In your pictures, the surfaces look somewhat yellow, especially when compared to other white items in your photographs. This would easily account for rather low blue readings.

  17. #17
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by NewBie
    In your pictures, the surfaces look somewhat yellow, especially when compared to other white items in your photographs. This would easily account for rather low blue readings.
    Yes, I noted that as well . It is the Clear Acrilic Spray that I used to protect the painted surface. Either it is not really "clear", or the two coats that I gave it caused the color change. Either way, it is too late and I will have to live with my mistake - it is what it is

    Will
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Hi,

    here is a sample of the same Fenix L1P light, as a digicam sees it.
    Red, green, Blue component and the overall in black.

    First is a beamshot on a yellowish white wall (Click for the large view)

    Note that blue component is diminished when reflected from a yellowish target.

    Second is a beamshot on a sheet of white paper


    Nice, even red/green/blue components on a white paper, also really white in real life.

  19. #19
    Flashaholic* chevrofreak's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Some light meters are not very sensitive to blue, while others are extremely sensitive to it. Perhaps yours is one of the less sensitive ones, while mine seems to be the most sensitive one according to the light meter benchmark passaround.

  20. #20

    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by wquiles
    ... All internal panels were sanded in between coats of white paint (4 layers), and then 2 layers of clear acrilic. The surface is not like a mirror, but it is very flat and even. ...ll
    Will,

    Very impressive, beautiful job! Are the coats of white paint latex or oil-based? If oil-based they will gradually yellow, though I'm not sure how that will be affected by the acrilic coating.

    Doug of Flashlight Reviews built a "milk carton IS" which he uses for his throw and total output tests. though his figures provide relative measure rather than actual lumens.

    Brightnorm

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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Yeah, that's what I thought too, amazing little birdhouse you've built with a huge raft of tecno-goodies.. congratulations! How many hours did it take you to build?

    BTW.. great pix too
    Celebrating the ROP.. 5 years of history

  22. #22
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Quote Originally Posted by brightnorm
    Will,

    Very impressive, beautiful job! Are the coats of white paint latex or oil-based? If oil-based they will gradually yellow, though I'm not sure how that will be affected by the acrilic coating.

    Doug of Flashlight Reviews built a "milk carton IS" which he uses for his throw and total output tests. though his figures provide relative measure rather than actual lumens.

    Brightnorm
    Thanks

    I don't have the spray cans any longer, but I suspect they were latex. I guess time will tell

    My Light Box also gives relative intensity readings, not lumens. I call my units "LBU - Light Box Units", since they don't mean anything else outside of my little bird house

    Will
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  23. #23
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    One limitation of my Light Box is that having a passive heatsink in a sealed environment means I really can't do really high power measurements for a long time, nor can I do burn-ins without fear of damaging the LED. Well, my Light Box is now capable of doing long runs as it now uses an "active" heatsink (fancy way to say that it uses a fan cooled copper heatsink!)

    I took a P4 heatsink:







    and "modified" to fit in my Light Box, replacing my main LED holder:





    I was extremelly lucky that the replacement heat sink is almost exactly the same heigth as the old one !!!. Since I designed the heatsink platform using a foam liner to take up some of the tension from the two spring loaded arms, the new heat sink works perfectly:







    I then mounted the fan underneat, so it provides nice, cool air right to where it is needed the most. For extended runs I will simply open the "port" hole which will allow the warmer air from exiting the enclosure, which I would of course close before taking a measurement. Since the heat sink/fan was designed for 75-100 watts from a P4, even with my modifications and fewer copper fins, it is still a massive overkill for LED testing, even over-loaded LED's







    Here is the final result. This last picture is not showing the centering foam on the perimeter of the new heat sink (which keeps it securely in place, for repetitive measurements), which is something I added and forgot to take an extra picture:



    I will be doing some tests over the weekend to compare to the data I have collected in the past to see if there is something different. I will report later my findings - I hope this works out!

    Will
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    A really brilliant job! I admire your innovative spirit and the work it took to put this together. Please keep us posted!

    "If you want peace, work for justice" - H.L. Mencken, Pope Paul VI
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  25. #25
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Thanks. This is actually just an update to the test platform. I have been using the box for several months now and have collected quite a bit of LED data with it

    Will
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    Flashaholic* mosport's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Very nice work Will, the new heatsink setup definately looks up to the job. Looking forward to the burn-in and extended run test results!



    I'll be mailing a few LEDs your way in a few weeks for sampling: UX0J and SX0H stars most likely.

    Derek

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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    wquiles
    This is a great project- thanks for the data.
    Good sized heatsink there...
    Reminds me of the old saying: nothing succeeds like excess!
    Kind Regards

    David

  28. #28
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    wquiles,
    Where did you get the holders?
    RC
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  29. #29
    *Flashaholic* wquiles's Avatar
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    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    Wood working store - Woodcraft, or something like that.

    Will
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  30. #30

    Default Re: My "Light Box" or poor man's Integrating Sphere ...

    where did you get that spring loaded arms ?

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