If at first you don’t succeed, try, try again

The roller coaster of the marbles tests

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.

As you can see, when we cut the current, the marbles came back to another position

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

I swear I could connect

Now that the Hall effect sensor is working and while the coils are still being tested with the marbles, we started working on our WiFi module. As explained in our project’s presentation, we want our devices to be able to communicate through MQTT with a backend and with other Touch.

The WiFi module :

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 keep feeling it

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.

Let’s connect it !Read more

Cause every time they flip, I get this feeling

Time for more tests with marbles

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

Can you feel it ? Yes we can !

In the components familly, it was time for the Hall effect sensors to be tested.

The sensor:

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

Marbles: “I can’t let you go, I want you in my life”

Designing our grid

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

I have a coil. I have a current => I have a magnetic field ! Wait, do I ?

A naive first approach

We received the coils denominated SDE1006A-681K. These are 680 µH inductance coils.

We roughly soldered two wires on each pole of the coil as you can see on the image below for very basic testing.

Next we needed to connect it to the IoT node. As a very basic montage for testing, we configured user button with polling on the IoT node to drive one of the GPIO pin we have on high when pressed.

We used a resistance to limit the current output. As we wanted a current of the ordre of the mA we used a resistance around 1 kΩ.… Read more

Touch, ready for components tests !

In order to start testing our components (Hall effect sensors and coils), we needed to decide which board and which OS we will use.

The Board:

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

How To Touch together ? MQTT is here.

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

Ah Qi, here we go again

After seeing Alexis, we noticed that the package of the previous component that we thought would do the job was based on BGA package… so we’re back to the previous step !

Basically the ideal component should :

  • be Qi compliant (low power profile and extended power profile)
  • have a 15 W power output
  • not have a BGA or CSP package which is definitely the hardest part

For a moment I thought I found the perfect match in the TS81000 : Qi compliant, up to 40W power output and QFN package ! Well yes, but actually no.

Alexis brilliantly pointed the fact that this component is only the auxiliary part of the receiver, and the other part which is the TS5111 has a WCSP package.… Read more