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LED Diffusion Hack Chat

Becky Stern will be joining us in the Hack Chat to talk about her experiences with LED diffusing! Bring your questions and comments.

Friday, August 17, 2018 12:00 pm PDT Local time zone:
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Becky Stern will be hosting the Hack Chat on Friday, August 17th, 2018 at noon PDT. 

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Individually addressable LEDs have become accessible, inexpensive, and easy to use. On full power, they can be eyeball-searingly bright! They are also small point sources of light that can lack character if left bare. This is why most LED light sources are diffused (or reflected), to shape the light for a suited purpose, whether it be a light pipe in an enclosure or the backlighting inside a costume prop. In this chat, we'll talk with Becky Stern about the methods she's used to diffuse LEDs.

Making and sharing are Becky's two biggest passions! Becky has published hundreds of tutorials about everything from micro-controllers to knitting. She's a New York City motorcyclist and unrepentant dog mom. 

Her work has been featured by numerous media outlets including BBC, CNN, The Late Show with Stephen Colbert, VICE, Business Insider, and Forbes. She works at Instructables.com (Autodesk).

  • Transcript

    L W08/17/2018 at 20:04 0 comments

    Lets get started! Thanks for joining us @Becky Stern ! While we wait for people to gather, could you tell us a bit about your work and what you do? and if anyone has questions they can go to https://hackaday.io/event/160157-led-diffusion-hack-chat)

    mpinner3:02 PM
    #sternSquad4evar

    Becky Stern3:02 PM
    Hi everybody! Thanks for joining the chat! I'm thrilled to be here.

    David Hunter joined  the room.3:03 PM

    Colin Alston3:03 PM
    I work on ill conceived and mostly impractical RF electronics

    Becky Stern3:03 PM
    I make tutorials about electronics, crafts, and the combination thereof. I've made so many wearables using LEDs that I have tried out many diffusion techniques over the years! I currently work at Instructables.com.

    Stephen Tranovich3:03 PM
    Wahoo, Hi everyone!

    Becky Stern3:04 PM
    Many of the techniques I have to share are documented in my recent guide here: https://www.instructables.com/id/13-Ideas-for-Diffusing-LEDs/

    Tom Hodder3:04 PM
    Hello

    Awesome. that link is great, theres so much there.

    Becky Stern3:05 PM
    Today I'd like to chat about paper, fabric, plastic, glue, glass, and 3D printing, just to name a few diffusion materials...

    Our first question is about materials! from @Morberis " LDPE in sizes larger than 24x36 seems to have a yellowish tinge, at least from Mcmaster Carr. Do you have a thickness you recommend?" I think you recommended LDPE as a defusion material?

    Sepah joined  the room.3:06 PM

    Becky Stern3:06 PM
    My background is in design-- I went to Parsons in NYC for undergrad, where I majored in Design & Technology. During grad school at ASU I started blogging for MAKE magazine and then went on to work at Adafruit and now Instructables.

    sfrias13:07 PM
    Great!! @Becky Stern Design->Adafruit->Instructables.

    GeekMomProjects joined  the room.3:08 PM

    Becky Stern3:08 PM
    Low-density polyethylene (LDPE) is the type of plastic used to make shrink film and food packaging. I've never ordered it from McMaster but imagine you could use any thickness you want, depending on the application...

    Becky Stern3:09 PM
    Sheet plastics can be sanded to cause more light refraction

    Horton joined  the room.3:09 PM

    Becky Stern3:10 PM
    When you're just starting out, it can be helpful to visit a plastics store in person to check out the materials

    jakemeadowsemail joined  the room.3:10 PM

    Our next question is from @Matt Ebel "I've been experimenting with pourable 2-part epoxies, pouring them into curved molds (silicone cupcake cups, etc) and then laying a NeoPixel ring on top of the liquid to create an attached lens that projects the ring's colors in specific ways. Right now it's all experimentation - I make a lens-ring combo, then I turn it on and place it facing a white sheet to see what kind of effect it has on the emitted patterns.

    Is it possible to use tools like blender or other 3D software to reduce the trial-and-error aspect of a process like this? Are there resources to get plastic optical parts made either to spec, or in generic 'standard sizes' that would fit over common led-ring PCBs?"

    Becky Stern3:11 PM
    Here in NYC the defacto go-to is Canal Plastics, but I've heard folks on the west coast praise Tap Plastics https://www.tapplastics.com/

    ... joined  the room.3:12 PM

    terrag joined  the room.3:12 PM

    Becky Stern3:12 PM
    What a cool technique! I'd love to see a tutorial about your workflow.

    Paul Stoffregen3:13 PM
    yup, Tap out here for retail plastics :)

    Becky Stern3:13 PM
    hey @Paul Stoffregen!! The legend.

    mpinner3:14 PM
    *swooooon

    Becky Stern3:14 PM
    Using 3D tools, you could create your own mold forms or a jig that gets embedded with the LED ring that stands it in the right position in the mold.

    ultimatefish67 joined  the room.3:14 PM

    chickey joined  the room.3:14 PM

    Chinna3:14 PM
    Does anyone...

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Keith Olson wrote 08/19/2018 at 22:49 point

(The video here ( http://www.candlepowerforums.com/vb/showthread.php?312940-Improving-the-DIY-integrating-sphere ) demonstrates just how effective using barium sulphate is.)

  Are you sure? yes | no

Keith Olson wrote 08/19/2018 at 22:34 point

FWIW, if you want to do indirect diffusion, 50/50 barium sulfate and white paint offers a good balance of reflectant and cheap.  https://www.triticeaecap.org/wp-content/uploads/2011/12/Barium_Sulfate.pdf

  Are you sure? yes | no

Scott Schubert wrote 08/17/2018 at 19:24 point

Besides Canal Street Plastics, what other stores in NYC do you like for wearables materials and supplies?

  Are you sure? yes | no

K.C. Lee wrote 08/17/2018 at 19:19 point

I used a sheet of fresnel lens bent it and used it to show a distorted light bar from some rectangular LED near its focal plane back in the old days.

  Are you sure? yes | no

mike wrote 08/17/2018 at 19:15 point

Last year at Target I saw some amazing Christmas decorations that had LEDs behind sheets of "prismatic" plastics and I've been wondering what that material is called ever since. The plastic had the texture of a fresnel lens, but made stripes of rainbow like a diffraction grating. Anyone know what that stuff was? 

  Are you sure? yes | no

K.C. Lee wrote 08/17/2018 at 19:22 point

Lol.  I used fresnel lens back when I was in university ages ago.  I didn't see your post until now.

  Are you sure? yes | no

Joshua Young wrote 08/17/2018 at 19:12 point

Do you have any design guidelines for getting uniform light dispersion? How many LED's per square inch vs materials. I would probably want the least LED's, so my material choice would be based of the highest even light vs number of LED's, but I don't know what is a good starting point of what works before you can see local bright spots.

  Are you sure? yes | no

scott.e wrote 08/17/2018 at 19:10 point

I've used a length of "clear" aquarium hose, split lengthwise and snapped over a multi-LED PCB to make a glowing light bar for a racing drone.

  Are you sure? yes | no

dante.rva wrote 08/17/2018 at 19:04 point

What would be your recommendation for shinning an LED through the back of a rhinestone? I had been considering using E6000 or a white silicone adhesive to diffuse the light. 

  Are you sure? yes | no

Mike Judge wrote 08/17/2018 at 19:04 point

Have you found any awesome off the shelf parts you can't wait to combine with LEDs but haven't had the chance yet?

  Are you sure? yes | no

Matt Ebel wrote 08/17/2018 at 18:50 point

I've been experimenting with pourable 2-part epoxies, pouring them into curved molds (silicone cupcake cups, etc) and then laying a NeoPixel ring on top of the liquid to create an attached lens that projects the ring's colors in specific ways. Right now it's all experimentation - I make a lens-ring combo, then I turn it on and place it facing a white sheet to see what kind of effect it has on the emitted patterns. 

Is it possible to use tools like blender or other 3D software to reduce the trial-and-error aspect of a process like this? Are there resources to get plastic optical parts made either to spec, or in generic 'standard sizes' that would fit over common led-ring PCBs?

  Are you sure? yes | no

Morberis wrote 08/17/2018 at 17:33 point

I've done some looking for things like this. It seems alot of what people recommend, like vinyl for light boxes, doesn't have great light transmission stats.

These are the best ones that I've found, I've listed the transmission % and the pricing if available below. 

PLEXIGLAS® LED (truLED) White WH14 GT, 47%, 45,93 GBP / m²
PLEXIGLAS® LED Clear 0M200 SC, 58%, 83,35 GBP / m²
3M™ Envision™ Diffuser Film, 3635-70, 30%, 50%, 60%, ???
3M™ Envision™ Diffuser Film, 3735-60, 30%, 50%, 60%, ??? 

  Are you sure? yes | no

CNLohr wrote 08/17/2018 at 13:07 point

Sadly, I won't be available right when it's going on, however, I did want to share our experiences at Unit-E making arcade games.  For really uniform lighting we found that tubes, sheets and chunks of LDPE couldn't be beaten.  Using sanded acrylic produces hot spots, UHMW gives a yellow tinge, HDEP is too opaque.  LDPE is just the most amazing, and easily machinable plastic for this sort of thing.  Except for edge lighting, then yes, milled or laser etched acrylic.  But I am really surprised it feels like LDPE is really overlooked in the maker scene...

An example shot of one of our machines: http://gaming.moe/wp/wp-content/uploads/2018/03/Unit-e_NeonFM.jpg

  Are you sure? yes | no

Morberis wrote 08/17/2018 at 17:30 point

Hmm LDPE in sizes larger than 24x36 seems to have a yellowish tinge, at least from Mcmaster Carr. 

Do you have a thickness you recommend?

  Are you sure? yes | no

itmaybeokay wrote 08/16/2018 at 17:20 point

For whatever it's worth, and I would wager many folks have already tried this one - but I've been using fairly generic office supply "Backlight Film" to get nice soft illumination from LED's. It's also handy to run through a printer for a backlit gauge scale (or similar). Its designed for backlit signage. 

  Are you sure? yes | no

foxpup wrote 08/15/2018 at 16:39 point

This blog is a great idea.  I'm posting here mainly to effectively subscribe to whatever anyone says about the diffusing light.  :-)

Personally, passing light through materials has been something I have preferred to avoid if I have the option of reflecting off of a surface like indirect lighting.  Whenever possible I prefer the indirect approach.  If the reflective surface is bright enough, there is minimal loss, but that solution does take some serious geometric creativity, but I'm sure the maker community is up to that. :-)

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