Specifications
The numbers
The Commander in full: what it drives, what it measures, how it fits in the boat and which radio channel does what.
Design figures from the circuit and data sheets. Nothing here has been measured on a finished board.
Commander
Specification
| Size | 80 × 52 mm, 1.6 mm thick, two copper layers. A 14 × 11 mm cut-out at one corner, under the Pico's aerial. |
|---|---|
| Construction | About 75 surface-mount parts on one face, with no resistor or capacitor smaller than 2 × 1.25 mm, placed by hand with a stencil and hot air. A Raspberry Pi Pico 2 W soldered flat to the other face. |
| Mounting | Four M2.5 holes. The 26 mm of board under the Pico reaches past the last pair. |
| Battery | 7 to 14 V. No reverse-polarity protection: use a polarised connector. |
| Through the board to BOAT | About 6 A, switched by the magnet latch |
| Receiver inputs | 8 servo-pulse inputs, 3.3 V or 5 V, buffered. Any function can be put on any channel. |
| Servo outputs | 2: front planes and rear planes, buffered |
| Tank drivers | 2 reversible motor drivers, current limited to 3.2 A each, 20 kHz drive. Each tank has a position-pot input and a stall guard. |
| Switched outputs | 8, each sinking up to about 300 mA, or about 100 mA each with all eight on. Outputs 1 to 6 switch battery voltage, or 5 V by solder jumper (0.5 A in total); 7 is the alarm lamp, 8 the buzzer. |
| Gas valve output | 2 A, with a diode across the coil |
| Water probes | 2 inputs, forward and aft, with a trip level set on the phone |
| Battery monitor | Warning voltage and cut-off voltage, both adjustable |
| Depth | Digital absolute pressure sensor with a tube port (CFSensor XGZP6858D). It reads to about 10 m of water in its catalogue 20 to 200 kPa version, and to about 15 m in a 20 to 250 kPa version if the maker will supply it. |
| Pitch | Accelerometer and gyro on the board (TDK ICM-42670-P). Mount the board flat, any way round, and choose the axis on the phone. |
| Control loop | 50 times a second, on its own processor core, with a watchdog that restarts the controller if the loop ever stops for two seconds. Wi-Fi runs on the other core. |
| Controller | Raspberry Pi Pico 2 W: RP2350A, 4 MB program memory |
| Setup link | The Pico's own 2.4 GHz Wi-Fi as an access point, page at 192.168.4.1. The same commands work over USB. |
| Firmware | Source published in full: an Arduino sketch and the setup page. Loaded over the Pico's micro-USB socket with its BOOTSEL button; no programmer needed. A RESET button on the board. |
| RX40 link | Three-pin header (GND, SCL, SDA, 3.3 V signals) for the RX40 receiver, when it comes |
| Power switch | Magnet and reed switch to turn on. Off from the phone, or by itself after a set time with no radio and no phone. |
| Regulators | 5 V at 2 A (switching); the Pico makes the 3.3 V. A solder jumper lets the 5 V feed the receiver and servos. |
| Planned pledge | £89, early bird £79 |
Fitting
Mounting holes
Four M2.5 holes, measured in millimetres from the top-left corner with the parts face towards you and the receiver pins along the top.
| Left pair | (3.2, 3.4) (3.2, 48.7) |
|---|---|
| Right pair | (53.9, 3.4) (53.9, 44.6) |
| Pico | On the other face, from 57.9 to 78.9 mm across. USB at the top edge, aerial at the bottom. |
| Aerial cut-out | 61.4 to 75.4 mm across, from 41.0 mm down to the bottom edge |
Use nylon screws and spacers no wider than 5 mm at the right-hand pair: they are close to the Pico's solder pads. Keep metal, batteries and wiring away from the corner with the cut-out.
Radio channels
As the firmware comes
Every function can be moved to another channel on the phone, and switch functions to another switch position.
| Channel 1 | Ballast tanks |
|---|---|
| Channel 2 | Dive planes |
| Channel 3 | Regulators on |
| Channel 4 | Trim |
| Channel 5 | Running lights |
| Channel 6 | Search light and aerial |
| Channel 7 | Torpedoes 1 and 2 |
| Channel 8 | Emergency ascent |
Coming later
Mini and RX40
Two more boards are designed. Neither is part of the planned campaign, and neither has a date or a price.
Mini
For boats with one ballast pump that runs both ways. Three receiver inputs, two plane servos, the same depth and pitch regulators and the same phone setup. About 51 × 31 mm as now drawn.
RX40
A 40 MHz FM receiver, 40.665 to 40.995 MHz in 34 channels, with a synthesiser in place of the receiver crystal. Eight servo outputs. 32 × 58.6 mm.
Want to back it on day one?
Join the launch list. It costs nothing and commits you to nothing. You get an email when the date is set and another the day the campaign opens, in time for the early-bird pledges.