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
In order to start testing our components (Hall effect sensors and coils), we needed to decide which board and which OS we will use.
Our project will not need to run any complex computation nor doing complex network communications. So almost all processors we checked could be used. We decided that it was better to take a controller little endian based on an ARM processor (because we are more familiar with arm’s instructions). We also wanted it to be low power and not too expensive. With those considerations, we went toward the STM32L475VGT6 because we already had boards at school with it.… Read more
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 🙂
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
The past week I’ve been looking through datasheet after datasheet in order to find several components that would fit our project.
Hall effect sensor:
Looking through the different types of hall sensors, I found that a switch sensor was the best fit, since we will use it to get the motor’s speed rotation, we only need to know when the magnet will be aligned with the sensor. The constraints we had on the choice of sensor were not numerous: we need a sensor with digital output, with 3.3V in input. However, one interrogation I have is whether or not the inductive power transmission will infer with the sensor.… Read more
In order to display animations that flow back and forth between several Phyllo, the Phyllos need first to be able to know each other’s position.
For now, we have reduced this problem to this : to display animations in the proper orientation relative to its neighbours, each Phyllo needs to know the direction of each neighboring Phyllo. They have no real need to know exactly how far they are from each other.
Associating detection and communication
It is not enough to merely detect Phyllos if the detection method doesn’t allow us to distinguish one Phyllo from another. We have to be able to both talk to a specific Phyllo AND know where it is physically located.… Read more
Here is a diagram summarizing the architecture of a Phyllo, to allow you to have a global vision :
This week, we spend a lot of time trying to choose the components. Here are the solutions we explored and the decisions we took.
Motor and ESC
All the animations we will display are based on two or three basic animations : aging petals, de-aging petals and possibly fixed images. Here are simulations to visualize those animations :
Aging and de-aging petals
In order to display those animations without skipping any petal (have a look at this instructable to remember the “skipping petals” part) while flashing the LEDs at 30Hz (ie 30 frames per seconds), the Phyllo has to rotate at :
We need to be able to drive our little magnet marbles and flip them according to a magnetic field direction or the opposite one. To do so current must be able to flow both ways through our self-inductances. Moreover we’re going to need current’s intensity of a much higher value than what is able to flow out of or flow in the GPIO.
One way to do so, is to use a H-Bridge as we can see on this site that we’ve already mentionned in an earlier post.
What’s an H-Bridge
Basically an H-Bridge is a electronic circuit built with drivable switches in a way that allows us to flip the voltage on a load and thus allows us to flip current polarity.… Read more