LitSimulate

LitSimulate is a simulator which simulates what LitSpin will display. We developed the first versions with PyOpenGL and PyGame.

Image Format

Each 3D image is represented by a classical image. If we note r the radial resolution (total number of columns), h the number of LEDs by column and n the number of steps by rotation, our image dimensions are rh x n. In our case r=20, h=32 and n=128. So we have 640×128. One line represents the n points one led will display. And each block of h lines represents the 360° image of a column from the outermost to the innermost (from 1 to r).… 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

Gobal architecture for LitSpin

In order to better understand how to make LitSpin a coherent and functionnal device, we created a diagram of its architecture .

The following represents how the different modules will communicate and work together. Technical details will come later as choices in components and communication buses are made. This is not supposed to be a drawing so it is not representative of how LitSpin will look but it should give an idea of how it will work.

Basically, there will be two main systems. A static system that will have an electric motor and what is needed to control it : a control board that will communicate with an Electronic Speed Controller, the accompanying BLDC motor, an IR receiver that will get information from the rotating system and the induction power transmitter.… 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

Generating 3D Models

TL;DR

  • We need to generate 3D models of phyllotactic patterns.
  • We give an explanation of how to generate phyllotactic patterns on a sphere.
  • We present an issue we encountered, and the solution we found.

Why 3D Models ?

When we first started thinking about the project, we quickly realized we would need to generate 3D models of the sculpture ourselves.

First because we need to have full control on the model, to try various configurations for the future 3D printed sculpture. And second because it will greatly help us visualize all the kinds of animations we are imagining.

Accordingly, Vlaya wrote a script using the blender python API to generate a 3D model, following John Edmark’s online explanation.Read more

Ah, yes. Stereoscopic vision.

This is a follow-up to my previous article, in which we explored the choice of PCB placement in order to get an optimal visibility.

My previous analysis only covered the case of a punctual point of view. However, most people have two eyes, which provide a double point of view and could increase our coverage of space. It is to be pointed out that a point of space seen by one eye does not provide depth information to the brain, however let us assume that our image perception is smart enough to overcome this limit.

In the following simulation, we used a typical eye distance of 6 cm.… Read more

Choosing a shape

As stated in this previous post, we have to compare different PCB dispositions to avoid blind spots. We soon came to realization that we would not be able to get rid of blind spots with our design, but it is possible to study the different ideas we came up with in order to mitigate this issue.

That’s why we created a python program that can simulate :

  • blind spots created by PCBs hiding each other
  • the variations of brightness due to the fact that LEDs can be seen at an angle (which is what created the dark center zone in CyL3D, which we are trying to get rid of)

Stairs : an iteration over CyL3D’s design

To avoid the issue of a dark zone due to all LEDs facing the observer at an angle in the center zone, an idea was to make sure that all LEDs were not facing the same direction.… Read more

Power and data transmission

One of the issues that LitSpin raises is power transmission between moving and static parts. One idea that came to mind was induction but we didn’t know whether integrated solutions existed and if they did, would they work with our power requirements.
Würth Elektronik offers a plug and play development kit that allows for 200W of output power which solves our power transmission issues.

Since the coils work using resonent induction, W.E. integrated frequency modulation in order to allow I²C data transmission. This could allows us to put the wifi module on a static PCB and get rid of the signal drops that were present on previous projects with spinning wifi modules.… Read more

Design Crisis

We discovered our first model contained a lot of issues. The outermost PCB often hide PCB behind them as you can see below. This results in some voxels being invisible. So we decided to create a simulator on Python to find the invisible areas. We will use it to determine the optimal configuration for our display. This configuration has several parameters such as the number of PCB, their position and the arrangement of the LED on one or both sides.

This a an example with 8 double-sided PCB in double spiral and 100 angular resolution. The blue dots are the visible voxels.… Read more