# 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.

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. And finally, I got an idea. If we put some metal pieces between the coils and the marbles, it would solve every problem.

On Monday, we try this assembly plan, and it works very well: with a 0.9A current, we could flip the marbles. This was really good news except for the fact that I did not try to flip the marble on the most difficult way to flip it: when every marble are on the same side apart from the marble on the centre and you try to flip it. Ilan tries this thing in the afternoon and it does not work. Again, we were in a dead-end.

## “It works! It works!”

On Wednesday, we explored every avenue to be explored, and we had no more idea: we tried with a homemade coil, with better metal piece than before (at first, we tried with a compression washer, then with a square of metal). Nothing works. The person in charge of the fablab gives us the solution: heating the marbles. We heat the biggest marbles we had a 300°C for 5 minutes and there was a real change in their magnetic strength. They do not attract each other from more than 2cm (before, we need to keep them at least at 10cm to avoid this thing). We finally find a solution to this big issue.

We choose two assembly plans for our next tests :

The first one is to put the marbles on a 2mm plastic sheet on the coils. For this, we need a 1.46A current and a 5V power supply.

The second one is to put the marbles on a 3mm plastic sheet with our metal pieces under it. We need a 0.9A current and only a 2.5V power supply.

## What’s next?

We are making two PCB to test our components if we used the 5V power supply or the 2.5V one. We will try the two on a 4×4 box and choose how we will continue our project. See you soon!