Step 7: Assemble Mobile
We found it useful to lay out one side of the mobile and mark the lengths of the dowels we liked, then cut two of each of the lengths we wanted (to mirror the mobile on the other side). Once you have the dowels at the lengths you like, tie the requisite parts at the ends of the corresponding dowels using fishing line. Secure the fishing line to the dowel with hot glue. Once you have all the components set, balance the mobile, starting from the bottom. Tie fishing line to the center of the bottom dowel, find the balance point, and glue the fishing line in place. Then tie this branch to the end of the medium dowel with the rainbow on the other end and secure. Balance this branch, then tie to one end of the other medium dowel. Balance the final light dowel and secure to the other end of the medium dowel. Finally, balance this branch and attach a servo horn directly at the balance point with fishing line and hot glue. Repeat this process on the other branch. Attach a servo to each end of the heavy dowel, using hot glue. You may find it helpful to troubleshoot the mobile assembly before attaching the servos to the horns, but eventually you will hot glue the servo horns to the servo shafts; this is necessary because of the weight of the branches, although the branches are not very heavy. Braid the three wires for each servo together and secure them along the thick dowel rod, having them meet in the middle.
Cut the remaining medium-weight dowel in half and attach one half to each side of the main heavy-weight dowel rod. Tape and/or glue the blacklights to the ends of the medium-weight dowel, facing towards the mobile. You will need to play with the angle of the blacklight heads somewhat to obtain a nice angle such that all the mobile pieces are hit by the blacklight. Twist the blacklight wires together and secure them to the rod, meeting at the balance point of the rod. Use fishing line to tie an LED to each end of the thick dowel and one in the middle, securing the fishing line with hot glue as necessary. Twist the wires for each LED together and make them meet in the middle. Twist all the wires from the LEDs, blacklights, and motors together and with the fishing line suspending the center of the mobile. These wires will all go to the arduino in the ceiling where the mobile is mounted. (Of course, if your ceiling does not have removable tiles like the one we used does, you will need some other place to store all your circuitry.)