Pumping out blog posts is tough when you're always coding, testing, and ordering supplies, so this one will be brief. We're reaching a point in software where we'll have full teleop control of the robot using an XBox 360 controller, but the sub requires three key electrical & hardware components before we submerge it: a power system, an expanded hull, and fancy connectors.
For the power system we're using four 3.2V LiFePo4 cells in series to produce the desired 12V to the hull. We'll embed two batteries each into two aluminum tubes and seal them with thermally-conductive potting compound. The combination should provide adequate heat sinking into ocean waters. We'll supply 12V unregulated to the thrusters and then regulated 5V to all the electronics. Two fuse boxes will separately protect the electronics and thrusters. We plan to use Seacon connectors for all connections into and out of the hull.
For the expanded hull, we bought a 6" outer diameter, 12" long, 1/4" thick acrylic hull, as well as a 1/8" thick polycarbonate tube. The polycarbonate tube was admittedly an impulse buy, and it's becoming clear that acrylic has better clarity and better pressure resistance. Polycarbonate has better impact resistance, but I don't plan on getting shot at underwater. Other Sean adjusted the CAD files for the endcaps and flange connector pieces to comply with both new tube sizes. We plan to send those to a local shop for cutting the general shape and screw hole taps. Later, after we figure out the power and thruster connection situation, we'll drill those holes in the endcap ourselves. He also altered the part that cradles the hull on the acrylic baseboard so that it supports a 6" diameter hull. We'll laser cut this part out of acrylic. All that's left to resize is the electronics tray that goes inside the hull.
As I mentioned, we're using Seacon connectors. Fortunately, they have a connector which supports six different three-prong connectors in a semi-circle-- almost definitely designed for our thrusters. In addition to the thrusters, we'll need a port for power in, control tether, lights (2), ballast control (2), and however many more for miscellany that will undoubtable pop up. Beware, these connectors can get pricey.
In other big news, the team is getting together for a mini-hackathon during the last weekend of January and first week of February. We're on track for a maiden voyage in the Spring!