Sprint 2

For the second sprint, we built an enclosure, increased the number of solenoids to 3 (intended to be 4), and switched from relays to MOSFETS since the relays required power from the Arduino to stay off and made a loud noise when they clicked on. We laser-cut a plywood and MDF box to hold the electronics and used plywood supports to hold up a horizontal length of acrylic tube used as the track for the magnet.

Solenoid Iteration

Our original solenoids were made of magnet wire round around a 3d-printed spool, but for the second iteration, we decided to remove the spools entirely and just have a larger, 2000-turn, coil of wire. To do this, we used a modular 3d-printed spool which separated into 3 parts after making the solenoid, covered them in petroleum jelly, and sealed the layers of wire with clear nail polish. Once the nail polish cured, we pressed the center of the spool out of the coil. While this method resulted in nice looking solenoids, we struggled to press out the center of the spool without unwinding some of the center coils, which made it difficult to slide the new solenoids onto the acrylic tube. This finicky coil-making process led to many unusable solenoids and we were unable to make the 4 we had initially intended to use for this iteration.

Control System Changes

Instead of just bouncing a magnet back and forth inside the tube, we started testing accelerating the magnet using multiple solenoids, which was now possible since we had 2 on one side of the tube. Calibrating the system involved shifting the solenoids on the tube, adjusting the duration of each solenoid receiving power, and adjusting the delay between solenoids triggering. In order for the magnet to accelerate while passing through the second solenoid instead of stopping and starting again, we needed the solenoid to power on early enough to attract the magnet then shut off exactly at the right time for the magnet to not get caught in the center of the coil. We found that there was an individual ‘sweet spot’ for each solenoid, and at any other position or timing, the results were erratic.

Horizontal Tube Iteration

We started work on designing our enclosure to hold the electronics and the acrylic tube. The electronics housing started out as just a simple laser cut box with butt joints. The supports for the acrylic tube were laser cut “eye bolt” style spokes that slotted into the top of the box with finger joints. We managed to consistently accelerate the magnet, but since we were unable to make a fourth solenoid, we only had a single one to return the magnet to the starting point, which was not consistent.