I’m trying to make a spherical LED array with a diffuser surrounding it, and I’m having trouble thinking of what I can use for the diffuser.
I want to a sphere approximately one foot across. This is an interactive object, so it needs to be durable - I anticipate people pushing the sphere around. I’ve got some ideas about how to make a spherical LED array, but I have not come up with any great ideas for the diffuser.
Constraints:
I want a sphere (or similar shape) approximately 1 foot across.
It needs to be durable - I’m going to mount it to a pendulum and I anticipate people pushing it around.
I need to be able to open it up - so that I can actually install the LEDs inside and easily service it if something breaks.
There are plenty of spherical acrylic diffusers out there (example), but they are all whole spheres with a small opening, so no easy way to build something inside of it.
I have found acrylic hemispheres that I could maybe use (example but A) I would have to somehow frost them myself and B) they use a flange to join them together which would be a bit ugly.
This person found something that seems just about perfect, but it was a one off that they found at a recycling company, I haven’t found anything similar online.
Do you have any ideas? The best options I’ve found so far are A) using acrylic hemispheres with a flange and just accepting the limitations or B) delving in to 3D printing (I don’t have a 3D printer, though, and it’s kind of a large shape to print.
I’m open to modifying my idea some (e.g. could use some other interesting symmetric solid like a dodecahedron or whatever), but I’m a bit stuck.
My first thought was of course a 3d printed sphere, could make it threaded to join 2 halves, with a set screw to keep it from being casually opened. The trick would be getting the thread seam about the same thickness/diffusion as the rest of the shell so it wasn’t too dark.
Yeah agreed, I think 3D printing would work, I just don’t have access to one (although if it’s the right way to go I can ask around).
I don’t think I need threading, I think it would be sufficient to just have a lip or ridge or something to make the two sides interlock - there will be a one-inch steel rod going through the middle of the sphere so I can just keep the two sides together by clamping the sphere at both ends.
it’s a good idea, i think it would probably work for diffusion. unfortunately i need it to be durable - strong enough that people can shove it without breaking it. paper wouldn’t work for that.
if i can’t figure out something better maybe i can do that and then make an obvious handhold somewhere else that people can push - there’s just a risk that they would push the diffuser anyway.
How spherical do you need it to be? Would something like an icosahedron (or higher side value polyhedron) constructed from foam work? There are a number of kinds of foam that diffuse light really well. If you need it to have more structure you could strengthen the edges of the faces with supportive strips made from wood or plastic.
If you start by constructing a flat, polyhedral net with the faces joined by tape or clear vinyl, you can leave a hinge for the polyhedron to open up on
hey that’s a great suggestion. i definitely don’t need a perfect sphere, just something that’s got a lot of rotational symmetry. polyhedrons built from foam sound like a good option, assuming the foam is strong enough. do you have any suggestions of materials (or suppliers)?
I started by thinking, “who else in the world has this set of requirements”. The first things that come to mind are pool toys and fishing equipment.
After a side trip exploring traditional Japanese round glass fishing net floats (really beautiful), a search for “clear hard plastic round floats” came up with this, which seems plausible.
(And, if I lived in the part of Shenzhen that is apparently filled with lighted inflatable ball factories, I’d definitely see if I could get them to make a small batch with embedded Pixelblaze displays. There are about a million of these things available, and they look pretty cool en masse.)
the round float looks like it could work. a bit smaller than i was thinking but i might be able to find a bigger one (or adjust my plans). would have to frost it myself but it seems doable. thanks!
I’ve only purchased a small sample from Etsy, but plastazote foam is designed specifically for LED diffusion and it might be worth googling around for sources. It will be a bit of work to make a large sphere that’s got a significant amount of structural integrity, but it seems like it should be possible.
You could start with an inflatable beach ball and lay on two or three coats of fiberglass and resin. The edges of the fabric will be visible but you could use regular shapes and patterns to make them seem an integral part of the plan. When you you feel it’s strong enough, just cut it in half and install your components.
Sounds like a fun project, good luck!