27MHz RC with dig. outputs and with telemetry
"development electronics"
This electronic equipment is used for development purposes. It supports simplex as well as half-duplex radio communication. An example of this is the transfer of the submarine’s pitch and depth controllers to shore. The radio section is based on the AX5043 transmitter/receiver IC, with which a half-duplex radio link is established. The following vessel data (process values) are transmitted to shore:
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Error status
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Battery voltage
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Depth (pressure sensor)
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Status piston tank end-limit sensors
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Velocity and pitch (3D accelerometer)
Piston tanks that are equiped with a sliding potentiometer or HALL sensors can be connected to the backplane PCB (quadrature decoding).
An absolute 5V pressure sensor with a differential output and an offset input can also be connected to the backplane PCB. The offset is used for atmospheric pressure compensation.
The backplane PCB also provides connectivity for 2x a water detector sensor (piece of wire), 4x piston tank end-limit switches, 7x digital outputs (ULN2003) and 7x servo's/ESCs.
An expansion port is also available.
For telemetry and control purposes a 6-axis IMU is used to measure pitch and estimate forward velocity of the vessel. The algorithm is developed in collaboration with AI. A key feature is that the speed estimate must be as immune as possible to rotational motion (waves) and drift between stationary periods. To achieve this goal, techniques such as complementary fusion and ZUPT are used, amongst others. In addition to wave immunity and drift there are many other requirements, conditions and assumptions to consider. Currently the algorithm has reached such a level of confidence that field trials are no longer an obstacle.
The PCB assembly has been optimised for installation in the Patrick Henry model submarine. To facilitate electrical connections, all connectors are located on one side of the backplane PCB. The surface area of the backplane PCB is 60 x 100 mm. The height of the backplane PCB with plug-in PCBs is 70 mm. The front plug-in PCB contains voltage regulation circuitry, the mid the micro-controller and the rear the radio.
The antenna in the model submarine is a shortened isolated wire dipole antenna for use inside the watertight compartment of a model submarine. It is optimised (dielectric constant) for mounting against/on the plastic material of the watertight compartment. The two dipole elements (330mm wires) are soldered on a small impedance matching PCB that amongst others provides galvanic isolation (MABA-11040). The antenna has been successfully tested for receiving and transmitting purposes and is also used as receive antenna in the non-telemetry RC option.
The last two images show a modified Robbe/Futaba F14 transmitter, which has a telemetry circuit board fitted to the outside. The smartphone is used to display the telemetry data. For this purpose, a serial-to-Bluetooth converter has been installed inside the F14’s casing.
