P18037: Team BASE (Biometric + Atmospheric Sensing Earphones)
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Preliminary Detailed Design

Table of Contents

Team Vision

Throughout the Subsystems-Level Design Phase, Team BASE has worked to accomplish:

Mechanical Drawings

A functional tree was developed in order to visualize all the drawings that will be required for a successful design.

 Mechanical Drawings

Mechanical Drawings

Document Updated by Andrew Zgoda

PCB Layout and Schematics

To measure SpO2 in the ear, two custom PCB boards were designed:

 In-Ear Sensor 3D View

In-Ear Sensor 3D View

 Main Processing Board 3D View

Main Processing Board 3D View

Sensor Feasibility Testing

PPG Sensor

 Red and IR absorption

Red and IR absorption

Principles of measuring SpO2:

1. Hemoglobin (Hb) and oxygenated hemoglobin (HbO2) differ in their absorption of red and infrared light (see Figure)

2. The volume of arterial blood in tissue (and therefore, the light absorption) changes during the pulse.

3. The ratio of red and infrared absorption correlates to SpO2.

PPG Sensor Hardware

PPG Sensor = 2 LEDs + photodetector

The photodetector measures absorbance of IR and Red LEDs. We need both AC and DC components to measure SpO2.

An R-value is calculated from the following ratio: R = (ACred/DCred)/(ACir/DCir)

The R-value is linearly correlated to SpO2 (see Figure)

Benchtop Feasibility Testing

 Possible PPG Sensor Placements

Possible PPG Sensor Placements

Procedure

Results

Sensor Placement Testing

Possible Placements

Location (2) Results

Temperature & Humidity Sensor

Benchtop Feasibility Testing

Procedure

The Environmental sensor was tested on a benchtop as well as mounted on the head. The head attachment device was comprised of a breadboard with the sensor and microcontroller attached. A bandana was utilized to secure the breadboard to the head.

Results

Pressure Sensor

Procedure

Results

Accelerometer/Gyroscope

Procedure

Results

 Accelerometer Sitting Still on Benchtop

Accelerometer Sitting Still on Benchtop


 Accelerometer Moving Fast, then Slow in X-direction

Accelerometer Moving Fast, then Slow in X-direction


Bill of Material (BOM)

The budget for our project is $3,500. So far we have spent $416.85 (See Figure for breakdown of purchases). Prior to design review 4, a more comprehensive list with future purchases will be developed.

 Items Previously Purchased

Items Previously Purchased

Project Schedule

The following schedule was developed to illustrate the tasks that need to be completed by the end of the semester (MSD I):

 Project Schedule

Project Schedule

Risk Assessment

Based off the chosen design, the following risks were identified. Actions to minimize each risk were developed and will be implemented.
 Risk Mitigation

Risk Mitigation

Design Review Materials

Plans for next phase

By Design Review 4, Team BASE hopes to accomplish the following tasks:

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