Week4

Week 4 Progress: Soldering and Initial Hardware Integration

Objective:
To assemble the hardware system by soldering key electronic components onto a compact custom circuit layout, with the goal of achieving a fully wearable and functional ankle monitoring device.

Implementation:

  • Design Decision:
    To ensure better comfort and wearability, I chose not to use pin headers, opting instead for direct soldering of all components.

  • Component Integration:
    Based on the approved component list, I soldered the following key modules:

    • Seeed Studio nRF52840 microcontroller (main controller)

    • Flex sensors (x2)

    • Resistors for voltage divider

    • Op-amp module (impedance buffer)

    • 3.7V Lithium battery connector

    • Type-C charging module

    • Wires and connectors for external integration

  • Challenges Faced:

    • Solder pads were very small, especially on the nRF52840 board, making precision soldering difficult.

    • In multiple cases, solder failed to adhere properly to the pad or formed weak joints.

    • During initial circuit testing, no voltage readings or signals were observed, suggesting connection issues.

  • Troubleshooting Steps:

    • Used a fine-tip soldering iron and flux pen to improve joint formation.

    • Applied low-temperature solder wire to reduce the risk of lifting pads or damaging the board.

    • Tested continuity using a multimeter for every connection, and reflowed any cold joints.

    • Resoldered the microcontroller power and signal lines, which resolved the no-data issue.

    • Verified flex sensor voltage divider output via oscilloscope, confirming live analog signal.

Results:

  • All components were successfully soldered and securely fixed onto the board.

  • Connectivity of all analog and power lines was confirmed via multimeter and voltage tests.

  • The board is now physically complete and functionally ready for code upload and system testing.

  • This hardware revision lays the foundation for future integration with the plastic wearable base and BLE communication.






 

Comments

Post a Comment

Popular posts from this blog

Week9

Image
Week 9 Progress: State Machine Design and System Modularity Objective To modularize the ankle monitoring code by implementing a two-state state machine (MOVING / STATIONARY) to detect whether the user is currently in motion or in a stable position for trend detection. The goal is to trigger alarm conditions only when reliable stationary measurements are available. Implementation: State Machine Architecture The firmware now uses a simple finite state machine (FSM) with two primary states: MOVING : The user is moving, sensor data fluctuates significantly, and trend evaluation is temporarily disabled. STATIONARY : The user is still. Trend data is collected to determine if ankle swelling is occurring. 📌 Transition Logic: Transition from MOVING → STATIONARY happens when sensor variation over a defined window is small (low deviation). Transition from STATIONARY → MOVING happens when at least 3 significantly different readings appear within the window (indicating movement or p...
Read more

Week14

Image
Week 14 Progress: Data Analysis and Final Testing Improvements Objective: The primary goal of Week 14 was to complete a comprehensive round of performance tests on the ankle monitoring system and to conduct a thorough analysis of the collected sensor data. Emphasis was placed on evaluating the system’s ability to detect swelling through trend analysis, as well as verifying the accuracy of filtering techniques in eliminating short-term noise. Alongside empirical testing, the effectiveness of the core embedded logic written in C++ was further validated. Implementation: A key element of the test was real-time monitoring of ADC (Analog-to-Digital Converter) output values from the flex sensor under simulated swelling conditions. The image below shows the plotted  sampled ADC values  and their corresponding  filtered values  (exponentially smoothed): From this graph, we can observe two trends: The  blue line  shows raw sampled data, which fluctuates significantly...
Read more

Week1

Image
Week 1 Progress: System Testing and Redesign Planning During the first two weeks of the project, my main task was to test the previous prototype and develop improvement plans based on its performance. The system consists of two main parts: a wristband and an anklet module. As shown in the figure, the wristband worked relatively well. Once worn, it was able to accurately display heart rate and blood oxygen levels, although the SpO₂ readings occasionally showed inconsistencies. In contrast, the anklet system had several issues. It frequently produced errors during testing and often triggered false alarms when tested with a 3D-printed cone-shaped object. Additionally, the circuit design was overly complex and bulky, making it uncomfortable to wear.
Read more