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

Choosing our components: “We are dwarfs on the shoulders of giants”

For our project, we need to test our components in order to find the best way to control our marble. Good news, our project has been done in other ways before. That’s why we take a look at this webpage: https://wiki.fuz.re/doku.php?id=projets:datapaulette:1bit_textile (in French)

Diameter of the marbles

Our first idea was to choose the smaller marbles, which have a diameter of 5mm. I have some of these marbles at home, so I tried to make a prototype with some cardboard.

Conclusion: my biggest fear was that a marble would move the other marbles when we rolled it (because of a too big magnetic field), but with my prototype, they don’t.… Read more

About LEDs

First ideas

Our original idea was to place LEDs on the inner sphere of the sculpture, either with flex PCB, or by drilling the sphere, placing the LED in the holes and connecting them with wires to a rotating PCB contained into the sphere. To facilitate the positioning of the LEDs, we could have modified the design so that we can pin the petals one by one on the inner sphere rather than print everything in one block.

But these designs are not easily achievable. First, Alexis does not know how to design flex PCBs. Second, to have a satisfactory visual impression, we would like to have at least 100 petals.… Read more