# LED powered light diffusion ring



## SRT Mike (Oct 15, 2011)

any optics experts here? 

I have a full CNC machine shop, and I have a need for a light diffusing ring. What I want to do is have an RGB LED (or multiple) mated to a diffusing ring that will surround a potentiometer on an instrument panel. As the user turns up the volume, the ring will change color from green to red.

I know how to control the LED - but I am unsure how to make the ring. Well, I know how to make the ring - that's not a problem, but how do I couple the LED to it and have the LED light evenly diffused across the surface area of the ring?

I tried side-mounting the LED into the ring and sanding the back of the ring - it looked sort of OK, but not nearly what I was looking for. I tried some 3M sign film for diffusing light and applied it to the back - didn't really work.

Is there a special kind of plastic to use other than plain acrylic? Or do I need a special contoured shape on the front of my light ring to diffuse light? 

I am trying to achieve this:

http://www.lumex.com/news/article/p...y_features_splash-proof_dual-color_halo_ring/

But they are $9-10 in "production quantities" and I need maybe 50... so I need to make something myself. 

Hope someone can offer advice


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## Ken_McE (Oct 15, 2011)

1.) Try putting diffuser over the front and a gloss white reflector in the back.

2.) They may be using a piece of plastic with a round cross section that has been bent in a circle - couldn't tell from picture.

3.) If you get it working, please tell us how you do it.


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## Harold_B (Oct 15, 2011)

Short of running a simulation, this guide might help you out: http://www.ciri.org.nz/downloads/Lightpipe%20design.pdf


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## FRITZHID (Oct 16, 2011)

could always use hacked up laptop/flatscreens, they've worked well for me in the past, just remove the LCD, and Polarizing films.


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## MikeAusC (Oct 17, 2011)

I would use plastic optical fibre - bunched together at the LED, spread around the circle.


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## SemiMan (Oct 20, 2011)

I expect they have a special optical surface coating that allows only partial amount of light to escape while the rest bounces in the ring. This creates near even light distribution around the ring and the nice even glow. There are some optical illumination fibers on the marker like this in that 2-10mm diameter range. However, they are flexible rods, not rings.

May be easier to have a bunch of small LEDs behind donut shaped diffuser.

Semiman


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