Good vibrations

Today Xavier and I prepared the setup for the integration of the speed feedback module and the Dshot sender, and the test of the hall sensor :

There is a circular magnet lended to us by Touch at the end of the screw. It generate a magnetic fields in a radial direction, which will therefore point towards the breadboard. It is pretty powerful so we hope it won’t constantly trigger the hall sensor.

The hall sensor we will be using is the TLE4964-4M. It is a pretty basic hall sensor with three pins (VCC, ground and output), which outputs a low value when the magnetic field exceeds B_OP , and goes back to a high value when the field drops below B_RP .… Read more

Steady, ready, capture !

I’ve been working on coding a section of a speed feedback system since Thirsday. We need a way to frequently measure the motor speed for two reasons:

  • To adjust the motor speed if it deviates from the target speed
  • To compute the precise time at which we need to flash the LEDs

To accomplish this, we have optical and hall sensors (we will use the sensor that gives the best precision) hooked up to our rotating PCB and our bottom fixed PCB. The rotating PCB is the one sending the commands to flash the LEDs, and the bottom is the one sending Dshot to our ESC.… Read more

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

3D printing tweaking

In my last 3D printing post, I showed you a sculpture printed with the new translucid filament we bought, and a first test gluing a filled petal to the shell.

The last shell had some major flaws due to wrong print settings, but we fixed it and printed another one:

This took 26 hours to print !

As you can see this one has support structure on the outside, this type of support is very easy to remove. The shell also has some support structure inside it, as with our first shell. It might be possible to remove these structures with acetone steam : acetone steam can be used to smooth a 3D model printed with ABS filament, and since the structure is made up of loose and messy filaments steam acetone might remove it, or at least smooth it.… 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

Figuring out the right WiFi protocol

Since thursday I’ve looked into how to implement the wifi communication we need between our phyllos (see Ruling the colony of Phyllos ).
We need a way for multiple Phyllos next together to broadcast data between themselves, and a way to communicate with the Phyllos from a smartphone or computer (for instance), and we will be using a ESP32 dev kit C integrated in our Phyllos.

Data exchange between Phyllos

The rate at which the phyllo need to exchange data doesn’t have to be very high at all: we just want to exchange small messages such as “Here is my ID: xxxx” , or “Start animation X at time T”.… 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

Final LED tests

Since we started doing research on which LEDs to choose for our project, there three different LEDs / type of LEDs we considered:

  • The LE RTDUW S2WP , requiring 1.4 A
  • The ASMG-PT00-00001, requiring 200mA
  • Four similar SMD PLCC 2 (the package compatible with the flexible waveguides we were considering) LEDs: ASMB-MTB1-0A3A2, HSMA-A431-Z50M1, CLM2D-GCC-CC0F0783 and ASMB-BTE1-0B332, all requiring around 20mA

The LEDs for the PCB petals (see our latest architecture post) were to be either the LE RTDUW or the ASMG-PT00, and the LEDs for the top PCB were to be the ASMG-PT00 or one of the four SMD PLCC2 LEDs.… 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

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