Overview

This vertical profiler was developed for the 2023–2024 MATE ROV season as a standalone underwater float for The Rays. The purpose of the float was to run a simple vertical profile, collect sensor data, and send that data back to a base station.

This project was an early version of the vertical profiler concept. It helped prove out many of the ideas that later became more refined in the 2026 vertical profiler, including compact electronics packaging, onboard data logging, remote communication, custom PCB design, and buoyancy engine control.

Goals and Design Requirements

The main goal of this project was to build a compact underwater float that could operate independently from the ROV. It needed to fit the required electronics, remain watertight, control its buoyancy, and communicate with a base station.

Requirements:

• Operate as a standalone underwater float
• Keep all electronics sealed and dry
• Fit the battery, electronics, sensors, and buoyancy engine inside a compact enclosure
• Use a pressure sensor to collect depth-related data
• Use an RTC to track time during the profile
• Use a base station to start the profile and receive data
• Include proper power protection, including a fuse
• Meet MATE ROV non-ROV device requirements

Design Process

This project involved a large amount of planning, design iteration, and troubleshooting. Early work focused on defining the subsystems, creating a task schedule, and organizing the team’s work through shared documents and project planning tools.

A major part of the process was comparing enclosure and penetrator options. The enclosure needed to be watertight, large enough for the required components, affordable, and practical to modify. Penetrator options were also compared based on sealing method, cost, cable size, and reliability.

This project also helped develop the design philosophy used in later profiler projects. Instead of starting with a fixed solution, the design process focused on identifying requirements first, comparing options, and then choosing the best solution for the application.

Mechanical Design

The profiler used a compact cylindrical layout with the main electronics, batteries, actuator, and buoyancy system arranged inside the body of the float. A custom internal structure held the components together and kept the layout organized.

The design went through several mechanical revisions. One major challenge was fitting all of the required electronics and batteries into the available volume while still keeping the float serviceable. The internal layout also had to account for antenna clearance, wiring, battery placement, and access to safety components such as the fuse.

The float also used custom aluminum parts, including spacers, actuator linkage parts, and external mounting pieces. These parts were cut from aluminum, cleaned, and anodized to improve corrosion resistance and durability.

Buoyancy Engine

The buoyancy engine used a syringe-style volume change system driven by an actuator or servo-style motor. By changing the displaced volume of the profiler, the float could control whether it descended or ascended.

The early control code used a simple mission structure. After receiving a start command from the base station, the float would descend while collecting pressure and time data. Once the descent condition was met, it would switch to ascending. After returning to the surface or reaching the final condition, the float would send the collected data back to the base station.

This system was simple compared with the later PID-controlled profilers, but it was an important step in proving that the buoyancy engine concept could work.

Electronics

The electronics were built around a custom PCB that held the required power and control hardware in a compact layout. The system went through multiple communication changes during development.

The original design used nRF24 radio modules, but those modules became unreliable and difficult to use consistently. The design was later changed to SparkFun SAMD21 Pro RF LoRa boards, which improved communication reliability and made the system easier to continue developing.

The float electronics included:

• SparkFun Pro RF microcontroller
• Pressure sensor
• RTC
• Temperature probe
• Buck converter
• Level shifting where needed
• Battery connectors
• External power switch connection
• Bottom switch input
• Buoyancy engine motor control

The power system used two 9V batteries with a series/parallel switch arrangement, a buck converter, and a 2A fuse. The fuse value was based on estimated current draw from the buoyancy motor, Pro RF board, and sensors.

Open the PDF.

The system included two main parts: the underwater float and the base station. The float handled sensor readings, timing, buoyancy control, and radio communication. The base station used another Pro RF board connected to a computer over USB and included a dive/start button and OLED display.

The float collected pressure and time data during the profile. The base station was used to start the run and receive the collected data after the profile was complete.

Software and Controls

The software was split between the float and the base station.

The float code handled:

• Radio communication
• Standby mode
• Start command detection
• Pressure readings
• RTC time readings
• Buoyancy engine motor control
• Descent and ascent sequencing
• Sending collected data back to the base station

The base station code handled:

• Radio communication with the float
• Connection checking
• Sending the start command
• Receiving profile data
• Displaying status information on an OLED screen
• Sending data to a computer over USB

This project did not use the more advanced PID and web-based control system that was later developed for the 2026 profiler. Instead, it used a simpler state-based control approach that made sense for the early version of the design.

Problems and Revisions

Several important problems came up during development. The first major issue was fitting all of the required parts inside the float while still meeting safety and serviceability requirements. This led to several layout changes and a custom PCB to reduce wiring and save space.

Another major issue was communication reliability. The original nRF24 radio modules were difficult to get working reliably, especially outside of basic lab testing. Because of this, the system was changed to SparkFun Pro RF LoRa boards.

There were also mechanical concerns with antenna clearance, button placement, battery location, and how to make the internal layout compact while still allowing the system to be assembled and tested.

These problems made the project a useful learning step. Many of the design decisions and lessons from this profiler directly influenced the later 2026 vertical profiler.

Final Result

The 2024 vertical profiler was an early but important version of the profiling float concept. It combined mechanical design, custom electronics, embedded software, radio communication, sensor data collection, and buoyancy control into one compact underwater system.

While the design was simpler and less refined than the later 2026 profiler, it helped prove the basic system architecture and showed what needed to be improved in future versions. The experience from this project helped guide later decisions about enclosure layout, electronics integration, communication, controls, and project planning.