Home made light box.

Discussion in 'The Projects Forum' started by Jonlate, Jul 10, 2018.

  1. Jonlate

    Thread Starter Member

    Dec 21, 2017
    45
    2
    Hi folks,

    So my wife wants me to build her a light box, so she can stencil over a light source, rather than doing it against the window.

    I made her one with a energy saving bulb, but it got to hot.
    I took apart a led torch apart and used the 4 LEDs that had, but it was only bright where the bulbs were.

    So now I want to start again.
    The box is about 10 inches by 7 inches, and I don’t mind if it’s powered by batteries, mains or dc.
    So.....
    1) if I wanted to build a grid pattern of LEDs, about 1/2 to 3/4 of a inch apart, what’s the best way of wiring them up? Should I use a ‘chip’ of some sort? What about using an Arduino?

    2) What ‘white’ led is best for brightness? Eg warm white, cool white, bright white??
    I have seen piranha LEDs with 4 legs on them, should I use these? Ordinary 2 leg ones? Straw hat ones? I would rather a focus LED rather than a wide angle one.

    3) I have seen rather nifty edge lit light boxes, but have no idea what they are using or how easy that is, so might just stay with the LEDs for now.

    4) any other things I should be looking out for?

    Looking forward to your suggestions, and possible wiring diagrams.

    Jon.
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
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  3. Jonlate

    Thread Starter Member

    Dec 21, 2017
    45
    2
    I did think about doing rgb LEDs, but you only really use white to see what you are stencilling underneath.
    This is also why the top needs to be solid plastic, so you can push down onto the stencil with the tools you use.
     
  4. wayneh

    Expert

    Sep 9, 2010
    15,002
    5,454
    I think I’d light from the top/sides and rely on a white background to diffuse the light. Direct lighting is always going to be tough to fully diffuse.

    You might try two layers of diffusion. Put another layer of diffuser between the light source and the drawing surface.
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,570
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    Use sign white acrylic diffuser as the top surface and add another layer of diffuser an inch below the top.

    Hey Wayneh already said that.
     
    wayneh likes this.
  6. Jonlate

    Thread Starter Member

    Dec 21, 2017
    45
    2
    So what sort of led should I use to get the best brightness I need to side light?

    I can’t light from the top as you need to see the stencil underneath, and your ( well not your head, my wife’s head) head will be in the way!!

    I am not sure what you mean by having two layers a inch apart? Any chance of a doodle to explain that?

    Thanks
     
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,570
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    Put the light source at the bottom facing up through a diffuser close to the light source. Put the second layer, which should be the working surface, approximately an inch above the first diffuser. Wide angle LEDs are best but with the right diffusers, not critical. I like bright, daylight white, anything from 5500 to 6500 Kelvin color temperature.
     
  8. wayneh

    Expert

    Sep 9, 2010
    15,002
    5,454
    Many LEDs are highly focused to produce a very bright but narrow beam. You want the opposite. But I agree that an intermediate diffuser can help get around that. It’s also possible to roughen or even remove the lens on the LED to disperse the beam.

    By “top” I meant inside the box, with the beam oriented from the upper edges down towards a bright white surface.
     
  9. whitehaired novice

    Member

    Jul 15, 2017
    247
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    I would make the box, as advised with two diffusing layers. But I would cover the bottom of the box with as many strips cut from a 5 meter 12 volt role of LEDs on a strip as will fit. The LEDs are staggered on the strip so you could offset one strip from the next to get a checkerboard pattern of lights.
     
  10. whitehaired novice

    Member

    Jul 15, 2017
    247
    29
    Sorry--I got called away mid-post.

    You will only need one 12 volt supply and you can usually get a dimmer when you buy the LED strip. You can cut the strips the length of your box and wire them in parallel--this takes a fine tip iron and a steady hand. The strips are marked every three LEDs where you can cut them.
     
  11. Jonlate

    Thread Starter Member

    Dec 21, 2017
    45
    2
    I think that’s what I will do.
    I will do use a strip of LEDs as the main light source, and have the two layers of diffuser.
    Just need to find the best thing to use as the first diffuser as was thinking of using 6mm glass as the working surface as it won’t mark over time, can get drawn on and rubbed off easy, and won’t bend.
    So what should I make the diffuser from?
    Thanks for the good suggestions.
     
  12. whitehaired novice

    Member

    Jul 15, 2017
    247
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    I think you will want more than one strip--I'd cover the bottom. Visit an Art supply house if you can and see what they offer. I have a vague recollection of a fake glass etchant you could paint on the inside of the glass which might work. Or a sheet of light grey plastic suspended a little over the LEDs.
     
  13. bertus

    Administrator

    Apr 5, 2008
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  14. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,570
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    Rosco makes a couple of diffuser films, one called Lumilux or Lumiflex if I remember correctly. I already mentioned sign white diffuser which it seems no one noticed is an actual industry term.
     
  15. oz93666

    Senior Member

    Sep 7, 2010
    234
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    The way to do this is to aim the led source away from the viewer , the box should be white inside , aim the light at the bottom or side of the box so it scatters ...maybe make a hole in the side of the box and have a torch outside aimed at the inside wall...

    Warm white is better ...
     
  16. MrChips

    Moderator

    Oct 2, 2009
    17,362
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    I have a light-box originally for viewing and sorting 35mm slides (remember those?).
    Build with translucent white Plexiglas acrylic on a slant and illuminated by two fluorescent tubes.
     
  17. -live wire-

    Active Member

    Dec 22, 2017
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    Have you considered something like this, using LED strips?

     
  18. Jonlate

    Thread Starter Member

    Dec 21, 2017
    45
    2
    Mr Chios - how hot do two strip lights get? Doesn’t it heat the plastic to much?
    Obviously not! What size box did you gave and what wattage were they?

    Live wire - that’s exactly what I need, I will watch the clips now and see if I can make it.
     
  19. -live wire-

    Active Member

    Dec 22, 2017
    828
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    You can always use less powerful LEDs to reduce the need for heat sinking and extend battery life (if it's battery powered). And if you have the tools to work with aluminum, go ahead, but you certainly don't have to make the housing out of aluminum. Just have some sort of heat sink if they recommend it.

    I recommend getting something like this LED strip. You will probably have to cut it and solder a few wires if you want it to be on a panel like that. It also comes with a dimmer and power supply.
     
  20. MrChips

    Moderator

    Oct 2, 2009
    17,362
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    Two 15W 18" cool white fluorescent lamps run cool.

    lightbox2.jpg

    lightbox1.jpg

    lightbox3.jpg


    Wooden base is 13" x 25" approx.
    Front panel is 6½" high.
    Back panel is 8½" high.
    Acrylic panel is 12" x 24" x ¼"

    I did not make this light-box.
    I am such a pack-rat I will salvage any and every thing that others throw away.
     
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