Last time, I wrote on this logbook, we were happy, we find a way to control our marbles without a side effect. But we did not think about one thing. With two marbles, our assembly plan works, however, with 9 marbles, it does not.
On Friday, after this discovery, I was thinking about this problem in my car: We need to keep the marbles near the metal because, without this, they will affect each other. On the other hand, we need to keep them far from the coils since we need to have some distance to make them flip.… Read more
To do our test we took an ESP32 Wroom-32 Dev kit C. The main purpose of this module will be to connect to the WiFi, receive through MQTT the images that the box will display and then transmit them to the STM32. In some cases, the STM32 will send to the ESP the state of the box and it will have to transfert those data through MQTT.… Read more
We previously tested a Hall effect sensor that, was working, but which gave us a voltage from which we could get the marble’s side. The issue with this is that in the final box, with all the marbles and the coils, we could have had strong pertubations that could alter the data. To avoid this issue we decided to use a sensor that would send the data through a communication protocol that could resist. We chose the TLE493DW2B6A0HTSA1 Infineon Technologies. This sensor sends its data through the I2C protocol so it should resist to our perturbations.
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 the components familly, it was time for the Hall effect sensors to be tested.
We used the SS39ET from HonneyWell. This sensor has 3 pins. One is GND, one is Vcc and the last is the output. The output is a voltage proportional to the magnetic field. We choose for Vcc a value of 3.3V.
First tests, let’s use a voltmeter.
To do the first tests we measure the output voltage with a voltmeter. To power the device we used a DC power supply. We also added an ampermeter to measure the current going to the Hall effect sensor.… Read more
Have you ever played with some neodymium balls? These are potent magnets, so we had to find a way to use them in our device without making them dependent on the magnetic field of another marble. Because if we had to manage this field, we would have always to power our coils, and they would have burnt. That’s why we choose to buy many different balls to try to find the best compromise between the distance and the diameter of the marbles.
With a plank of beech, we cut with a laser engraver. We made many different holes of many diameters with various distance to know which one is the best.… 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
One of the most critical part of the project will be the communication. Whether it is between the Touchs of with the backend we need our device to be able to communicate.
The communication challenge:
The first thing we had to do was to choose the protocol. As we wanted to allow both a communication with a backend and between devices, we chose the MQTT protocol. It has the advantages to be easy to use and to easily allow us to switch from listening to the server to listening an other device.
The first step: the broker:
In MQTT, all devices (may it be a server or an actual connected thing) are clients.… Read more