Pressure Vessel
The pressure vessel is 8" outer diameter with ⅛" thick wall and 1' long. I was able to get this from Amazon for ~$501 I got a largish panel of ¼" acrylic from which I’ll be cutting/routing circles for the two ends. There’s a laser cutter in Mountain View I can use but not sure how I’ll do the routing yet. Still need to look into an O-ring and clamps.
Motors
I just bought another three 500 GPH 12V bilge pumps2 which brings me up to six in total. Also got three amazing PicoBorgReverse3 motor controllers! Each one can drive two motors. For now I’m planning on just running four motors with two controllers. Tested with two motors and one controller so far and it’s fantastic. Still need to print/buy propellers - probably going to just buy them.
Pressure Sensor
I got a 5V 175PSI pressure sensor for ~$30 on Amazon4 Went through all the trouble to voltage divide it down to 3.3V before realizing the Raspberry Pi doesn’t have analog input GPIO… So turns out the Arduino Nano will be needed after all… Meh
Software
ROS on the Raspberry Pi is finally up and running! I won’t be using ROS on the Nexus 4. Instead, the sensor app will talk over USB using Android Open Accessory Protocol. I’ve almost finished libraries to facilitate this communication on both sides.
Misc
Ordered some reed switches5 to do the mission toggle without need to cut through the pressure vessel. Also ordered a tri-state buffer IC6 that I think I can use to build a water sensor where the reading is always high while there’s no water. I like that because it will read low when it’s not setup correctly and when there’s water.