On Thursday and Friday, I continue to work on the H-bridge code for the test PCB and finally find a way to implement some timers that should stop the current in the coil.
I also have to go to Télécom to cut another box for testing so that we can even work with the closing of our school. However, we do not have the cable and a battery, so even if our code may work, we cannot make our tests. We hope we could take it at school this week.
Now, I will merge my code with Ilan and Zennedine and I will try to implement a watchdog too that will halt the coil even in debug mode.
On Thursday, I launched the cutting of three planks with the laser cutter. We finally have to change the size of the box. With the coronavirus, we cannot ask for a 510x510mm PCB, so we choose to make a 450x450mm PCB and a 14×14 box.
I also ask for many estimates for cutting a Plexiglas plank and we should finally cut in the same way this plank since the price will quadruple.
Finally, I change the upper part of our 4×4 box too.
While waiting for the test PCB, I have to find something to do. Our laser cutter is only 30cm large for 610cm long, so I find a way to cut our wooden plank it in three ways. I hope that there will be no need to add something, but if the plank bend, we will have to put some wedge in the middle of the plastic plank.
I also have to unbend the wood. We ship a 3m plank that came wound, so I make something like this
I also cut a plastic plank for our test box
And made a better scheme with CorelDraw for those who want to make the same device
At last, I take a look at Ilan code for the beginning of a thread that will check the state of all the box.
On Thursday, I went to Telecom for the first time of the week. I took advantage of this journey to print the prototype of our box for the test PCB. But I lack plastic plank for the middle part (in green in other photos), so we need to wait for a week to have it. However, we will have it on time because we won’t have the PCB before.
In the afternoon, I began the final PCB. We found before a component for charging the battery on a USB cable (the LTC4088), that I put in the schemes.
After some hours on it, I finally find how to import a DXF file of our PCB.… Read more
On Monday, I began to have a look at a 16×16 device scheme. For this, I took the 4×4 scheme, I copied it 16 times, and I added two multiplexers. One that will multiplex the SCL signal to the multiplex that controls the Hall effect sensor, and one other that will multiplex the multiplexer that controls the H-bridge drivers. Then, I had some questions.
Should I keep a pull-up or a pull-down between two multiplexers or not? My answers for this moment is to keep a pull-up in order to avoid a clock signal on SCL if there is some latch between the two multiplexers.… Read more
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
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
Last time, I made a prototype of a box, but there was a problem with the size of the holes for the marbles. They were bigger than the marbles, and they would fall if we put the box vertically. I tried to put the coils and the marbles at a lower level and to reduce the size of the holes. But with this, we have too much friction, and we cannot flip the marbles easily.
The person in charge of the fablab offers to make a printed support for the marbles in order to reduce friction.… Read more