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Glass Bead Diffusion Experiment

PostPosted: Sun Mar 19, 2017 11:03 pm
by Andrew Davie
I had an idea a while back to use tiny glass beads in front of the LEDs in the lightbox to perform diffusion. As I currently have a single red LED pulsing via the MC4151 digital potentiometer, I thought I'd put it in the 3D printed lightbox assembly and have a look to see if the glass beads did diffuse the light well. I had the beads just loose in the original bag they came in - thickness about 6mm at a guess. Beads are about 2mm diameter. Anyway, it came out well - just a single LED but I'm hopeful that the beads as a "barrier" between the LED array and the disc will perform well.

I killed my magnificent ultra-bright LED matrix earlier today, which is a bit of a shame. But impetus to build a better replacement. Better, in that I want to drive my Arduino televisor from a single 12VDc supply, so the lightbox needs to run off 12V. I have a lightbox with a precise curved arc window exactly matching the nipkow hole spacing, so I can create a LED matrix that also mirrors this and minimises the LED usage. I can get away with 5 strings of 3 LEDs each, and as the LEDs I am using are at a guess about 2.2V each, that will work well. And the total current requirement will be 125mA. So I'll start building that soon.

Here's the video of a single LED behind the glass-bead diffuser running in a bit of dim light because it's really not that bright otherwise. But you get a good idea of the diffusion being reasonably even over the entire window, and no glaringly obvious central bright spot. Also this is inside the 3D printed lightbox with the precise curved display window. One other thing, the inside of the lightbox is painted with silver paint to assist with reflection. I should do that to the circuit board too before I wire it up.

Re: Glass Bead Diffusion Experiment

PostPosted: Mon Jul 30, 2018 11:55 pm
by FlyMario
Well, that is fantastic. In the long run, did it pan out for you?

Re: Glass Bead Diffusion Experiment

PostPosted: Tue Jul 31, 2018 10:56 pm
by Andrew Davie
FlyMario wrote:Well, that is fantastic. In the long run, did it pan out for you?

I barely remembered this until I saw the video! It was good at diffusing, but I did not end up using it in anger. I found the layers of greaseproof paper to give a better result, particularly when I went with the super-bright LEDs.