New Year, new skin

Happy New Year everyone, hope you enjoyed the holidays !!

Today we are going to talk about the latest trends of our hardware architecture.

New PCB disposition to drive the petals

We used to try to drive each LED with its own processor. However we could not manage to get every component to fit on the PCB petals. Moreover, the processors were underused as we barely needed half of their timer outputs. Therefore, further inside the Phyllo, we decided to add a layer with slightly bigger PCBs (let’s call them the petal controllers). They have a STM32F207VIT6 which can drive up to 10 LEDs. The PCB petals then only hosts a LED and transistors, capacitors and resistors. We have 12 petal controllers and 62 PCB petals.

The two layers of PCBs with matching colors to represent the driver/driven relationship
Transversal cut of the Phyllo

Other specifications

The top PCB

This PCB will hold two STM32F207VIT6 and will drive 16 LED independently as well as one (or maybe up to three) other LED for the remaining baby petals a the very top of the structure which are driven as one block.

Other Processors

The processor for the main PCB (the lowest of the rotating PCBs) is STM32H743 and the one for the fixed PCB is STM32F103CBT6.

IR detection

We will put at least one IR emitter on the main PCB so that it emits towards the top of the structure. The IR will then be diffused at 360° through the 3D printed structure. As for the IRDA, it will be put on the bottom side of the main PCB. That way there will be minimum interference between the IRDA and IR detection. Moreover, the LED used for IR detection emit around 950nm whereas the IRDA works under 900nm. Nevertheless, the IR emitter has got quite a large emission band and goes under 900nm albeit less intensely.

Power supply

We will use a LiPo 4S. We hoped to use a 3S but the motor cannot run with the delivered voltage. (It actually runs for around 5 to 10 seconds before stopping.) We will also use an external charger for the battery but will add a direct sector power supply.

Then, to lead the power to the rotating part, we will use ball bearings. They will be doubled to mitigate micro cuts of power supply. Also, at its arrival on the main PCB, there will be huge capacitors and coils as well as power regulators. As a consequence, the battery will never directly serve the pic power consumption due to the lighting of LED. The capacitors on the rotating structure will have to bear all the strain. Thanks to this, we will not have to use large wires to supply the rotating structure. 

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