Feature: Communications
Figure 4: Measurements made in swimming pool Figure 3: OnSemi radio transceiver
which, to some extent, determines the board’s operational frequency. The radio transceiver offers auto-ranging – i.e., adjusting the frequency within certain limits – which typically takes place during transceiver initialisation/startup. The PCB supports a wide variety of supply voltages such as
regulated power supplies as well as rechargeable batteries. For underwater range measurement, I used two floating
platforms, mounted with PCBs, a battery and other components. The antenna can be vertical or horizontal, attached to two tubes underwater used for adjusting antenna depth. A bright flashing light on the platform indicates the quality of the communication. When the distance between the two platforms becomes too great, the light will blink irregularly.
Software development tools To successfully control the model submersible, a GUI and interfacing with hardware (USB/serial port/steering stick) are required, which calls for a good library of mathematical and control functions. These requirements led me to MyOpenLab, an open-source alternative to LabView that uses Java. Java enables the development of application software
regardless of the platform (Windows, Linux, etc.). A nice feature is that MyOpenLab also supports some hardware from Raspberry PI, Velleman and Arduino. But, there’s also room for improvements, such as introducing a zoom function and enabling greater visibility of the connection lines between elements. After installing MyOpenLab, I was soon able to send
data and make a run-time version of the test program. By placing several elements in a sub VM, programs can be kept manageable; using sub VMs is very similar to that of macros. The input and output pins can be connected to the upper
VM layer. I used JDK8 from OpenLogic, which also contains JRE (Java runtime environment) needed to create run-time
36 February 2022
www.electronicsworld.co.uk
Figure 5: Impression drag measurement hull submersible [Image credit SINTEF]
executables. For text-based programming, Lazarus could be a good option since it is also open-source, see https://www.
lazarus-ide.org/ (the site is actively maintained and developed, unlike MyOpenLab).
Results and applications I have successfully tested a simplex underwater radio connection over a distance of 6m with vertically-arranged dipole antennas at a depth of 70cm (27MHz/50mW). T e measured range matches the theoretical range. Despite the shallow depth, it is unlikely that radio waves propagated just above the water surface because a greater range would then be expected. A follow-up test is scheduled for spring 2022, and it
concerns a half-duplex radio connection at 27MHz/50mW at depth of 2m, where a payload of 16 bytes is transported back and forth at 30Hz. This test is already prepared and is functioning in air. When the on-shore antenna is placed in the air, the range
is more than sufficient for various uses, either by hobbyist or maritime research centres. If both antennas are submersed it is easier to comply with radio regulations but then the range is too small for model submersible hobbyists.
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