PCB and Scheme

Finishing the test_PCB

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

E pur si muove !

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

New discoveries

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.

As you can see, instead of 1,35A, the coil used almost 2A

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

More tests on coils

First box prototype

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

Working on a pre-alpha v0.01 backbone

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

Some tests before the prototype: Let’s PCB

A Test PCB

Before making our first device, we aimed at having a smaller one to test some components we do not have time to test: h-bridge, multiplexer, etc.

So, I had to complete a Test PCB that Alexis began. We already have chosen the components, and he chose the step-down converter, which we would use for our circuit.

I spend two days for placing and routing this PCB. We had two constraints: to put our coils at a precise place and the hall sensor just under them and to add the other component where there was still someplace. We choose to try to not add a battery since a phone charger can give us a 5V voltage with 1,5A current.… Read more

And if you still don’t succeed, try and try again

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

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

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

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