Going all out on the 3D

As mentionned here, we will use 62 LED mounted small “Petal-PCBs” and 12 “processor PCBs” to drive groups of 4 to 7 Petal PCBs. Now you might be asking “how on earth will you assemble all these PCBs and solder all the wires involved on a structure rotating at 30 rotations per second ?”, and that would be a fair question…

Along our reflexion we had multiple ideas:

  • Add structure to our 3D printed shell on which to stick the PCB: we had to drop that idea after all the problems we encountered printing our shell
  • Make the axis go all the way up and have arms stretching from the axis to hold the PCBs: this would’ve made the structure quite heavy, and we were not sure how to design this
  • Make the PCB hold by using rigide wires to link them: This was initially proposed only for the PCB-petals, but even for them we were not convinced it would hold
  • Print another solid shell with structure to hold all the PCBs: this was problematic since it might delay or block the IR emitted by the IR LEDs we wanted to place inside the shell

Finally, we decided on the latter option, as we will probably have the IR LEDs emit in a gap between the PVC plate and the large aluminum top platform.… Read more

A new shell fresh from the oven

You might remember we printed a Phyllo shell with success a week ago. The material we used for this shell however was not meant to be translucid, but actually phosphorescent. This meant our shell was not as translucid as it could be, and it’s phosphorescence was also problematic since we want a high contrast between the phyllo when lit with inner LEDs, and when not lit by any light source.

We therefore ordered a more suitable 3D filament. This time the result for the shell printed with this new filament was not as successful:

The deformation on the first picture was probably caused by the temperature of the nozzle (from which the filament goes out) being too low, which caused the printed raft below the shell to detach itself from the platform.… Read more

If at first you don’t succeed, try, try again

The roller coaster of the marbles tests

Last time, I wrote on this logbook, we were happy, we find a way to control our marbles without a side effect. But we did not think about one thing. With two marbles, our assembly plan works, however, with 9 marbles, it does not.

As you can see, when we cut the current, the marbles came back to another position

On Friday, after this discovery, I was thinking about this problem in my car: We need to keep the marbles near the metal because, without this, they will affect each other. On the other hand, we need to keep them far from the coils since we need to have some distance to make them flip.… Read more

3D printing : behind the scenes

As mentionned in A solid foundation , we printed our first full-scale sculpture last friday, and it was a success.

We were relieved because there were multiple factors that were not 3D printing-friendly :

  • Our scultpure needs to be hollow, because we need to be able to put all the PCBs and LEDs in it
  • Not only should it be hollow, it needs to be translucent, and thus very thin
  • The thickness should also be relatively constant in order to have uniform lighting
  • The sculpture has several parts which are almost horizontal

Why were these problematic ? Well, let’s see how 3D printing works

Slicing

The first step in 3D printing is to create a .stl… Read more

A solid foundation

Last week we met with Alain Croullebois, the go-to guy for mechanical questions at the school. We went to his workshop with the motor we received during the holidays : this Turnigy Multistar 4225-390Kv 16 Poles Multi-Rotor Outrunner. We discussed what the physical structure of the Phyllo could look like.

Here is a global diagram of what we came up with :

The mechanical structure of the whole Phyllo

The Base

For the base of our Phyllo, he suggested stacking two 30cmx30cm aluminium plates 8mm thick, with a separation of 6cm between the two plates maintained by 2cm wide pillars at each corner.… Read more

Cause every time they flip, I get this feeling

Time for more tests with marbles

In my last post, I was a little sad. We were about to abandon the heart of our project: marbles because they were too powerful. Alexis gives us some hope by saying that we may have better result with some iron. So we try the configuration on the right (there is an iron plate between the two marbles), but it gives bad results. The iron does not constrain the magnetic field. It just attracts more the two marbles. We were about to try with some steel when the miracle came…

The miracle came from coils

In fact, the coils already have some iron on them.… Read more

Marbles: “I can’t let you go, I want you in my life”

Designing our grid

Have you ever played with some neodymium balls? These are potent magnets, so we had to find a way to use them in our device without making them dependent on the magnetic field of another marble. Because if we had to manage this field, we would have always to power our coils, and they would have burnt. That’s why we choose to buy many different balls to try to find the best compromise between the distance and the diameter of the marbles.

With a plank of beech, we cut with a laser engraver. We made many different holes of many diameters with various distance to know which one is the best.… Read more

Taking full control on our 3D model

We discussed in our post Generating 3D Models  the script I wrote to generate the 3D model of our phyllotactic sculpture. In this script, I start by generating a polyhedron made up of quadrilaterals arranged in a phyllotactic pattern:

Then, my script takes as input a 3D model of a petal and copies it on each quadrilateral:

The 3D model of the petal I use is taken from John Edmark’s model

One problem with this method is each quadrilateral is different, which means I had to slightly deform each petal to fir the quadrilateral’s shape. Figuring the exact 3D transformation to accomplish this seemed a little too time consuming so I used lattices in blender, which are a way to deform objects according to a 3D grid.… Read more

The PCB puzzle

We made a few major modifications in our design : it turns out flex PCBs aren’t possible. Even though everything isn’t quite decided yet, here is a summary to clarify the situation. I will keep you updated of any major modification 🙂

General design

A Phyllo is composed of three parts:

  • a fixed base,
  • a rotating half sphere placed on this fixed base serving as support for the lighting of the sculpture,
  • a hull made of petals that covers this sphere.

A Phyllo has 78 petals that can be illuminated individually (8 spirals with 6 petals lit by spiral arms, or 13 spirals in the other direction).… Read more

A false sense of symmetry

Although our initial plan to light the petals was to put waveguides between the petals and LEDs placed on a flat rigid PCB (see “About LEDs“), Alexis recently told us using flexible PCBs might be possible.

Flexible PCBs could be placed directly on the inside of the demi-sphere of the sculpture, thus avoiding the use of waveguides and ensuring a good luminosity. Their drawbacks however includes a high cost and the fact that Alexis hasn’t yet used them for previous projects.

Using flexible PCBs, our idea would be to take advantage of the symmetry of the sculpture and place identical PCBs along each of the 13 spirals.… Read more