Phyllos Galore

One has holes in it, one was printed in the wrong material (phosphorescent ), one got too small after our acetone smoothing test, one got warped due to wrong temperature settings… and the last one seems just fine, but might potentially explode in a thousand pieces when we’ll try to spin it at 30 RPS 🙂

We would like to thank the Zortrax M200 who spent 120 hours in total printing these, hopefully it will get some rest one day (not today though, we still need to print a bunch of supports )

Improving the 3D PCB supports

I talked in this post about the 3D supports I’m making in order to easily fit the 62 petal PCBs and 12 processor PCBs in the Phyllo. Since then, I’ve made quite a few changes and progress on the 3D design:

Here you can see both the phyllo, the support for the processor PCBs (blue) and for the petal PCBs (red), and the PCBs (green)

The cylindric pieces are here in order to have thickness around the holes in which I will put the threaded inserts.

I tried to print the processor PCB support, but it failed because of wrong settings, here is the result of the second print:

It’s not perfect yet, there is one spot where the structure got shifted, but it’s still a very promising result.… Read more

Random GDB behavior

We just got a new dev board: a Nucleo144 STM32H743ZI. We will use it for all the code which will run on the STM32H743VIT6 processor of the main board.

Before anything else, does anyone know why I keep getting “Program received signal SIGTRAP, Trace/breakpoint trap 0xfffffffe in ?? ()” half of the time after I flash a simple “hello world” program on the STM32H743 and execute it on gdb (using continue) ? The other half of the time it works just fine.

Anyway, back to the article. After carefully memorizing all of the 3289 pages of the reference manual (as would any good ROSE student do), I started coding the module which will send SPI frames to the processor PCBs (see the Software Architecture post).… Read more

SPI protocol to light all the LEDs

We started looking into how to implement the SPI communication between the main board and the processor PCBs with Sibille, Xavier and me.

Et each turn of the motor, we need to light up all the 78 RGB LEDs during around 100us at the same time. The motor can spin from 11 RPS to 30 RPS. We have 3 SPI buses leaving the main board, and each SPI bus gets split into at most 5 processor PCB (the top PCB can be counted as processor PCB), and each processor PCB has at most 24 colored LEDs.

SPI frame

Every SPI frame has 16 bits, and we decided to use the first 3 bits as PCB processor addresses, the following 5 bits as colored LED addresses, and the last 8 bits to encode a color.… Read more

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