Project Name: HydraWise

Project Functional Description:

Hydration is critical for maintaining performance and safety, particularly during physical activities or in extreme environments. However, determining individual hydration needs and whether to consume water or an electrolyte-based drink is often subjective and imprecise. This project aims to address this gap by developing a wearable hydration sensor, coined HydraWise, that provides real-time, personalized hydration recommendations based on sweat biomarkers and physiological data.

The primary target users are athletes and active individuals who face varied hydration needs. Real-time hydration monitoring can optimize endurance, reduce physiological strain, and enhance recovery by maintaining an appropriate hydration and electrolyte balance. This is especially vital during endurance sports or physically demanding activities, where improper hydration can impair performance and disrupt thermoregulation.

The project will involve designing and prototyping an embedded system consisting of a custom PCB, a microcontroller, and integrated sensors. Through the use of a LED heartrate monitor sensor, the wearable component, a wristband, will collect data on the user’s heart rate. Similarly, using a conductivity sensor, the wristband will also track the user’s sweat conductivity. After preprocessing of the data is done, all data collected will be transmitted wirelessly by the ESP32 microcontroller via a built-in Bluetooth module to an iOS mobile application. The system will analyze the data, and the app will display hydration and heart rate data in a relatively “real-time” fashion through a User Interface with hydration recommendations and heartrate data, as well as historical trends, supporting up to 24 hours of logged data. To demonstrate the system’s functionality, test scenarios will include collecting user sweat data or using vials of water with varying electrolyte concentrations. The design ensures compliance with ECE 47700 requirements, including functional integration and real-time data processing.

The power system in HydraWise is designed for a stable and efficient energy management system to ensure continuous monitoring of heart rate and hydration status. The project incorporates a lithium-polymer (LiPo) battery, which serves as the primary power source with connection to a buck-boost converter maintaining a stable 3.3V output. The regulator ensures that the components of the system are receiving only their operating voltage throughout the whole battery life. Additionally, the battery is integrated with a 'fuel gauge' (also known as a coulomb counter) which will monitor the battery's charge level. This component will then transmit the data to the microcontroller, who will transmit the data to the app so user can track the wristband's usage. Along with those, there will be an integrated circuit on board that will take care of charging, meaning that when the user hooks up a USB-C cable, the IC will control and supply constant current to the battery, and once the battery is charged, it will switch to constant voltage to maintain 100% battery percentage until the user starts using it again. This IC comes with protective components as well to ensure the battery won't get damaged. These power system prevents unexpected shutdowns and ensures uninterrupted hydration tracking, making HydraWise a reliable and user-friendly wearable hydration sensor.

The mechanical housing component of HydraWise will be 3D printed using Thermoplastic Polyurethane (TPU) at the Bechtel Design and Innovation Center. TPU is chosen for its flexibility, durability, and resistance to abrasion, making it ideal for wearable devices. The housing will securely encase the electronic components, including the microcontroller, sensors, and battery, while allowing for comfortable wear. Additionally, the device will feature a silicone Apple Watch band for a secure and adjustable fit on the user's wrist.

One "stretch" functionality of HydraWise's hardware includes interfacing the battery with a 'fuel gauge' integrated circuit for enhanced battery management using the I2C communication protocol to track battery usage levels efficiently. Enhanced battery management systems work to monitor the LiPo battery's charge state, voltage, and overall health. By periodically polling the battery management system (BMS) via I2C, the microcontroller can assess charge levels and estimate remaining battery life to send to the phone over bluetooth to display in app.

Project Specific Design Requirements (PSDRs):

1. PSDR #1 (Hardware): Using a 400mAh Lithium Ion Rechargeable battery in collaboration with a buck boost converter to maintain a constant 3.3V output.
2. PSDR #2 (Hardware): Interfacing microcontroller and heartrate sensor using I2C communication protocol.
3. PSDR #3 (Hardware): Interfacing microcontroller and conductivity sensor using the Digital to Analog Converter to source a signal and the Analog to Digital Converter to read the output of the sensor.
4. PSDR #4 (Software): Receiving and storing data transmitted from the microcontroller to the phone via BLE. Data will be converted to json format and stored in a local database for historical insights.
5. PSDR #5 (Software): Using Xcode and Swift to create an IOS mobile app to display hydration and heart rate data, including hydration recommendations.
6. Stretch PSDR #1 (Hardware): Interfacing microcontroller and Battery Management System IC with I2C communication protocol to track battery usage levels.