Date of Award

6-2024

Document Type

Thesis

Publisher

Santa Clara : Santa Clara University, 2024

Department

Electrical and Computer Engineering

First Advisor

Andy Wolfe

Second Advisor

Jessica Kuczenski

Abstract

As a result of global warming and rising ocean temperatures and sea levels, seaweed forests are degrading. Seaweed biomass loss presents significant risks to coastal communities that rely on seaweed forests for food, livestock feed, fertilizer, and more. Marine Permaculture is the Climate Foundation’s regenerative farming initiative to grow seaweed outside of its intended habitat. The “Deep Cycling” technique involves positioning a submersible bed near the water surface during the day and lowering it at night, allowing for seaweed to receive sunlight and cold water. Prior work on this project included establishing a temperature control loop, though did not include a telemetry system. Therefore, this design did not include real-time feedback or error correction. An acoustic modem is used as a low-cost, low-power solution to establish continual monitoring and feedback of water conditions to reposition the submersible seaweed growth bed to optimal seaweed growth conditions. This process involves sending temperature data using a piezoceramic transducer, modulating data using frequency shift keying, and receiving the signal using a piezoceramic hydrophone. Data is demodulated by an STM32 microcontroller which operates a motorized winch accordingly, repositioning the submersible growth bed. We demonstrated underwater transmission of binary signals up to 57 meters using carrier frequencies of 18 kHz and 22 kHz to represent a binary 0 and 1, respectively. Future work for this project should demonstrate underwater telemetry up to 600 meters, which would require sourcing an appropriate amplifier to transmit a carrier signal with 60 V peak-to-peak amplitude.

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