by Web FishMar 16, 2013 @ 12:34pm
Controls the direction and power of the propulsion pods. Translates the central processor decision making and the battery power into mechanical movement.
- Current selection: Pololu Simple Motor Controller 18v7
- Status: Undecided (under testing)
- Criteria: Max current handling, standard I/O, small physical footprint, thermal footprint, cost
- Finalists: Pololu RoboClaw 2x5A Motor Controller, Arduino Motor Shield R3, SeeedStudio Grove Motor Driver
- Main decision factors: High sustained / peak currents, cost, standard serial bus interface

(click image for larger view)
Spec highlights:
- Simple bidirectional control of one DC brush motor.
- 5.5 V to 30 V operating supply range.
- 7 A maximum continuous current output without a heat sink
- Four communication or control options:
- USB interface for direct connection to a PC.
- Logic-level (TTL) serial interface for direct connection to microcontrollers or other embedded controllers.
- Hobby radio control (RC) pulse width interface for direct connection to an RC receiver or RC servo controller.
- 0–3.3 V analog voltage interface for direct connection to potentiometers and analog joysticks.
Caveats:
- Still unclear if we will use UART or PWM to control the boards. We are using 2 pins either way;
- If using UART, both boards will be chained;
- Unclear if hat signature will be an issue until we mount in the navionics bay with the rest of the electronics modules;
by Web FishJan 6, 2013 @ 02:03pm
Provides information about about momentary vessel orientation with respect to the earth's magnetic field (compass), as well as earth's gravitational field (accelerometer). Basic navigation instrument.
- Current selection: LSM303DLHC 3D Compass and Accelerometer
- Status: Finalized
- Criteria: Sensitivity, standard I/O, small physical footprint, cost
- Finalists: Sparkfun HMC6352, Sparkfun LSM303 Breakout Board, Pololu LSM303DLHC 3D Compass and Accelerometer
- Main decision factors: Cost, standard I2C bus interface

(click image for larger view)
Spec highlights:
- Dimensions: 0.5" × 0.8" × 0.1" (13 × 20 × 3 mm)
- Weight without header pins: 0.6 g (0.02 oz)
- Operating voltage: 2.5 to 5.5 V
- Supply current: 10 mA
- Sensitivity range (configurable):
- Accelerometer: ±2, ±4, ±8, or ±16 g
- Magnetometer: ±1.3, ±1.9, ±2.5, ±4.0, ±4.7, ±5.6, or ±8.1 gauss
Caveats:
- Still unclear how well (if at all) the tilt compensation will work in a constant motion (sea waves) environment;
- Unclear whether we'll be able to use built-in accelerometer to determine vessel orientation up/down (current flip status) - again, due to constant acceleration changes from riding surface waves;