Last week, I made a lot of routing to finish our first test PCB. We choose with Alexis to make a PCB that would work with an alimentation because it was easier, so I had a lot of more things to do, but after some work, I finished this part.
Scheme of the box
In order to understand better the design of our box, I made a scheme of the organization if you want to try to do a Touch at home with this design.
This was not clear in my previous post, but this design allows the marbles to flip when the box is put horizontally and vertically.… 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
After more tries on Tuesday, I found a way to flip the marbles vertically. I tried to use again the plastic part, without results. I make a huge comparison of all the configuration we tried before and at last, I shift a little the marbles from the coils, and with this, they flip in an easier way, even vertically, with a hole of 9.9mm. After finishing this, we can now concentrate on the PCB and the other problems of conception and programmation.
The shifted box is a box with the coils, a disk of metal, a 2mm plastic plank, a 3mm plastic plank (in green) with holes of 12mm of diameter, shifted of 5mm.… Read more
On Monday, I tried many new configurations. One of them was to make an ellipse that would improve the result when I put the box vertically. But I have one big issue: with the painting, the marbles have a lot of friction and I cannot even flip them with some old configurations that were working. So we may have to make a choice: keeping a hole in the wood bigger than the diameter of the marbles and we cannot put the box vertically or finding a new way to paint or a new way to keep the marbles in the box.… Read more
Last Friday, I tried to improve the design of our box because we want it to be functional vertically. With a spacing of 8mm between the plastic plank and the wooden plank, I manage to have some result. But before having this result, I burnt the coil I was using, by energizing the power supply too much with an old configuration. So this coil increases its current consumption, and I need to test again with another coil.
I also tried to use an element made by the person in charge of the fablab, but the marble cannot flip in it, because it needs to have the possibility to move, it cannot just flip around its axis of rotation.… 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
Zennedine finds a way to use our coils, so I tried to make a first box to check if it will not collapse. I made this and I checked if the marble flip or not, and it works.
Coils no more available
When we begin our project, we ship some coils, the 74458303 but in a short time, we cannot ship enough coils for the project. So I tried with the same configuration to use the 74458304 coils, and it works, even if there were more edge effect (the nearest coils flip sometimes). With these coils, we need only 0.59A… 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
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
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