I’ve Come to a Reliable Conclusion upon working on CRC yesterday. Don’t try to understand what’s going on. Many walked this path before me, and yet I couldn’t look away at the promised cognitive pleasure of understanding it. In the end, I was denied this pleasure and here I am, left in frustration.
Well I might be a little bit exaggerating, but I’m sure that I’m miles away from having a grasp solid enough on CRCs to implement my own. For those who would want to do so though, this article from Barr’s group seems to stand as a reference, or at least a reliable entry point on the subject.… Read more
Lately I’ve been working on a way to make the communication between the STM and the ESP more reliable.
While searching on the subject, I came across two methods.
The first one made me reminisce some of the lessons we had in first year about information theory. The idea is to use a Hamming code for the messages of the protocol. This will make the communication more robust because of the properties of such a code. We plan to use a Hamming code (7,4) which means that the words will be 7 bits wide, with 4 bits of information (meaning we can go up to 16 different words, including the words with only bits at 0) and 3 bits of parity.… Read more
Last friday I mainly worked on getting the new marbles (the ones that hadn’t undergone any heating process) to the desired magnetic field values. Remember, on this post I had already manage to have the marbles we already heated at the desired value. It needed a heating time around 5 min, so I instinctively thought that for marbles that had undergone no heating, it would need a longer time. I was wrong. And not slightly wrong, but more like completely wrong.
So I started heating at 300°C for 6 mins, it was too much and the magnetic field almost completely disappeared (barely noticeable).… Read more
Wednesday I worked on trying to have all our marbles with roughly the same magnetic field, something around 20-40 arbitrary unit (as measured by the sensor).
After slightly changing the mount so I could have the marbles on a fixed point, I went on and measured the magnetic field of all our marbles. Because our marbles were heated with different processes we had a wide range of values.
With this montage, I sorted the marbles going from 20-40, 40-60 and so on to 100-120 a.u.… Read more
After finding a configuration that could do the job as discussed on the previous post, we needed to validate it.
To do so and as such, to decrease randomness and have the best repeatability possible, I started working on some kind of mount. After a little while I had a first version of this and did some measurement with the Hall sensor. I noticed that the positioning of the Hall sensor was unpractical as it was free to move.
That’s why I did some laser cutting and cut a hole to fit the breadboard in it in a wooden plank, just under the coils.… Read more
After trying to reproduce the results we had in this post we noticed some problem of repeatability. It was less frequent than the previous but still at a level we couldn’t ignore and that would cause future problem.
After working each on our own during the morning, I met with Alexis, Henri and Ilan in the E-lab/Fab-lab to further investigate the problem.
It turned out that we spent the afternoon testing dozens and dozens configuration. The parameters we changed were : spacing between marbles, marbles diameter, thickness of the plates we put the marbles on, material of the plates, stacking of the plates, using or not using little round metal plates (non ferromagnetic) to try to canalize magnetic field.… Read more
Because we wanted to create a design centered around aesthetic for our device, we chose to implement wireless charging for our battery.
There are plenty of ways to implement WPT. First of all there is near-field power transmission and far-field power transmission.
For our project, we will focus on a near-field power transmission. In this field, one of the most common technique is inductive coupling. But it is not the only one : capacitive coupling is an interesting technique for our project.
Capacitive coupling VS inductive coupling
Because inductive coupling is based on converting AC current to a magnetic field, there is a high risk that it will cause strong interferences and perturbations with the magnetic fields of the marbles, thus complicating our control over our device.… Read more