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Diffusing a diy RGB LED? — Parallax Forums

Diffusing a diy RGB LED?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-12-03 14:36 in General Discussion
So I was going through a book and some of the exercises called for an rgb led which I dont have I figured I could take a red green and blue led and then solder the ground togather encase it and put a diffuser over the top, problem solved. The thing doesnt need to be perfect but i need to be able to make it mix the RGB colors to make new colors so I was wondering if there may be a good house hold material for this?

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2012-12-01 15:51
    - wax paper -
  • prof_brainoprof_braino Posts: 4,313
    edited 2012-12-01 16:01
    ping pong ball if you just want it to glow
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-12-01 16:04
    rw,

    You didn't say whether you want the colors mixed when illuminating a surface or when you are looking directly at the LEDs. The latter requires more diffusion than the former which, in fact, may require no diffusion at all, depending upon the angular output of the LEDs.

    But, yeah, wax paper is good. A piece cut out of a gallon milk jug might also work, as might white tissue paper or half of a ping pong ball. BTW, multiple thin layers of diffusive material spaced apart work better than one thick layer for the same transmissivity.

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-12-01 17:40
    Grinding the dome (lens) off the top of the LEDs may help with diffusing the light.

    Here are a few more materials you could try.

    Polymorph or a piece of clear plastic with sanded surfaces.

    (I've only tried grinding the dome off myself (I think I learned it from one of JonnyMac's articles).)

    BTW, even if the three colors are all in the same LED doesn't guarantee the colors will be well mixed.
  • John A. ZoidbergJohn A. Zoidberg Posts: 514
    edited 2012-12-01 19:31
    Sandpaper the LED until it gets real rough. Let the light ray scatter like mad.

    Or, cut a small portion of a glue stick, and then make a hole, allowing the LED to be fit inside. That thing makes a primitive diffuser, but it works.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-12-01 23:40
    well im just using standard parallax rg, then a vidhay blue with a real tight viewing angle i think 15 or 30 degrees, maybe ill filevthe domes off as duand suggested thend sand with 800 grit and diffuse with a layer of wax paper and milk jug. im just trying to get an even color around the whole diffuser, a nice ambient bulb. i think the hard part will be choosing a resistor for each that sets them all near the same luminosity
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-12-01 23:46
    i think the hard part will be choosing a resistor for each that sets them all near the same luminosity
    Just tweak with all of them on until you get "white" from the mixed colors without a tint.

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-12-02 00:02
    i think the hard part will be choosing a resistor for each that sets them all near the same luminosity

    I generally run RGB LEDs at 5V since some of the blue & green LEDs have a forward voltage very close to 3.3V.

    With 20mA LEDs (at 5V) I usually use 150 ohm resistors on the red LED with 100 ohms for the blue and green.

    As Phil mentioned the individual PWM values can be changed in software to get a good looking white.

    With my 8x8 array I used $FF, $CF and $3F for the RGB values to make white.

    (Your posts can be difficult to read with all the typos.)
  • ercoerco Posts: 20,259
    edited 2012-12-02 04:44
    Duane Degn wrote: »
    (Your posts can be difficult to read with all the typos.)

    +1, generally incl. no caps or punctuation.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2012-12-02 05:34
    ...maybe ill filevthe domes off as duand suggested thend sand with 800 grit and diffuse with a layer of wax paper and milk jug. im just trying to get an even color around the whole diffuser, a nice ambient bulb.

    The non-destructive options should be the first considered.
  • ZetsuZetsu Posts: 186
    edited 2012-12-02 11:11
    take a straw cut it up... Slide leds into straw peaces... DIFFUSED ! ( oh wait isnt that wut u doo wif a booomb ) !?
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2012-12-02 12:17
    That would be defused.

    But he needs the result to be diffuse, not the LEDs (separate R, G, and B).
  • ZetsuZetsu Posts: 186
    edited 2012-12-02 12:29
    PJ Allen wrote: »
    That would be defused.

    But he needs the result to be diffuse, not the LEDs (separate R, G, and B).

    The part about a bomb was a joke.....

    The ultimate goal is to take a concentrated light source and spread it out over a larger area, correct ? Cutting a straw up in to peaces and putting each led into one, and putting a bead of superglue over the top will do just that.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2012-12-02 13:49
    The ultimate goad goal is, in his words (Reply #7), "...a nice ambient bulb."

    Piece out.
  • ZetsuZetsu Posts: 186
    edited 2012-12-02 14:06
    PJ Allen wrote: »
    The ultimate goad is, in his words (Reply #7), "...a nice ambient bulb."

    Piece out.


    My bad, I missed the part about him wanting to consolidate them into a single housing/bulb.

    Well buy a straw in a larger diameter....

    http://www.brianmicklethwait.com/images/uploads/DrinkingStraws.jpg
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-12-02 20:33
    Or Poly Ice maker tubing .. Comes in all sizes .
  • NWCCTVNWCCTV Posts: 3,629
    edited 2012-12-02 20:45
    Duane Degn wrote: »
    IAs Phil mentioned the individual PWM values can be changed in software to get a good looking white.

    With my 8x8 array I used $FF, $CF and $3F for the RGB values to make white.

    Can you ellaborate a little on how to code this using a BS2 stamp? I would like to try it out on a few different colors of LED's.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-12-02 21:22
    NWCCTV wrote: »
    Can you ellaborate a little on how to code this using a BS2 stamp? I would like to try it out on a few different colors of LED's.

    I'm not really sure how to do this with a BS2.

    I'm not sure if my syntax is correct or not. I'd think you'd use something like this:
    main:
      for x from 0 to 255
        if x < 256      
          HIGH redPin
        else
          LOW redPin
        endif ' is this needed? I think so
        if x < 208
          HIGH greenPin
        else
          LOW greenPin
        endif
        if x < 64
          HIGH bluePin
        else
          LOW bluePin
        endif
    goto main
    

    I added one to each of the brightness values to get to work out correctly (I think).

    I don't know if the BS2 if fast enough to keep the LEDs from looking like they are blinking.
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-12-03 10:21
    well im just using standard parallax rg, then a vidhay blue with a real tight viewing angle
    One thing I've done before is put a a blue LED behind the R/G LED, since they tend to be pretty diffuse. The blue shows through the lens of the R/G, and mixes nicely. If you need to not have leakage from the sides, heat-shrink the whole thing so only the front of the R/G LED is visible.
  • ercoerco Posts: 20,259
    edited 2012-12-03 14:36
    Duane Degn wrote: »
    I don't know if the BS2 if fast enough to keep the LEDs from looking like they are blinking.

    Sure it is: http://www.youtube.com/watch?v=iDXY6l7IxJ8
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