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

Table of Contents

Team Vision for System-Level Design Phase

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

Functional Decomposition

A functional decomposition was generated in order to identify the major subsystems within the design.

 Functional Decomposition

Functional Decomposition

Live Document Updated by Andrew Zgoda

Benchmarking

Product Benchmarking

Benchmarking of current headphones on the market was performed in order to supplement concept generation and selection.
 Technical Benchmarking

Technical Benchmarking

Our selected concept will definitely need to include Bluetooth 4.0, weigh no more than 10 oz. and retain a form factor consistent with social norms. The selected concept should attempt to be water resistant and have a battery life greater than 8 hours in order to be competitive with current devices on the market.

Sensor Benchmarking

Sensor Metrics Dimensions Interface Accuracy Range Current Consumption Cost (per unit)
STMicroelectronics LIS2DHTR 3-Axis Accelerometer 2 x 2 x 1 mm I2C or SPI ± 0.040g ± 16g 2-185 µA $1.59

Analog Devices ADXL345

3-Axis Accelerometer 3 x 5 x 1 mm I2C or SPI ± 16g 25-130 µA $9.95

STMicroelectronics LSM6DSL

3-Axis Accelerometer and Gyroscope 2.5 x 3 x 0.83 mm I2C or SPI ± 0.040g ± 16g 290-650 µA $4.09

Grove

Temperature, Humidity, Pressure 40 x 20 x 15 mm I2C or SPI ± 1hPa, ± 1°C, ± 3% 300-1100hPa, -40-85°C, 0-100% 0.4 mA $17.00

Bosch BME680

Temperature, Humidity, Pressure 3 x 3 x 0.95 mm I2C or SPI ± 3% 300-1100hPa, -40-85°C, 0-100% 8.9 µA

Bosch BME280

Temperature, Humidity, Pressure 2.5 x 2.5 x 0.93 mm I2C or SPI ± 3% 300-1100hPa, -40-85°C, 0-100% 3.6 µA

Sensirion STS3x

Temperature 2.5 x 2.5 x 0.9 mm I2C or SPI ± 0.3°C 0-65°C 6.6 µW

Analog Devices ADT7410

Temperature 4 x 4 mm I2C ± 0.5°C -40-105°C 2-210µA $1.36

STMicroelectronics LSM6DSL

3-Axis Accelerometer and Gyroscope 2.5 x 3 x 0.83 mm I2C or SPI ± 125-2000 dps 290-650µA $4.09

Bosch BMG160

3-Axis Gyroscope 3 x 3 x 0.95 mm I2C or SPI ± 125-2000 dps 5 mA $5.39

STMicroelectronics L3G4200D

3-Axis Gyroscope 4 x 4 x 1.1 mm I2C or SPI ± 205-2000 dsp 6.1 mA

LTR-390UV

UV Sensor 2 x 2 x 0.7 mm I2C ± 20% 2300 counts/UVI 100-110 µA

Vishay VEML6070

UV Sensor 2.35 x 1.8 x 1 mm I2C 5 µW/cm^2/st 100-250 µA

Concept Development and Selection

In order to determine the best design solution (in terms of ingenuity, feasibility, cost and time), various concepts were generated and systematically reviewed before choosing a solution.

Morphological Table

A Morphological Table was developed by incorporating ideas gathered during benchmarking as well as unique ideas suggested by team members. The purpose of this exercise was to identify unique combinations of alternatives.

 Morphological Table

Morphological Table

Document Updated by Andrew Zgoda

Pugh Analysis

At this point in the design process, the sensors of interest had been researched and selected. Therefore, the only design challenge remaining revolved around the form factor. Three alternatives were chosen from the Morphological Table above, which included the occipital band, the necklace and the neckband. A Pugh Analysis was performed in order to choose the best form factor based off the customer and engineering requirements (selection criteria).

 Pugh Concept Selection

Pugh Concept Selection

Document Updated by Tegan Ayers

Ultimately, a decision regarding form factor will need to be postponed until sensor-location testing can be performed in the next Design Phase.

Feasibility Analysis

How much current will the device require?

Component Consumption
BT Module 9uA
PPG Sensor 600uA
Environmental Unit 3.6uA
Accel/Gyro 650uA
Microcontroller 0.2mA
TOTAL 1.4626mA

Estimated Battery Life = (Battery Capacity/Current Consumption) x (0.70)

Estimated Battery Life = 9.5 hrs

How much storage do we need on the device?

Metric Rate (samples/min) Data Generated (bytes/min)
SpO2 60 240
Temperature 1 4
Pressure 1 4
Humidity 1 4
Accel/Gyro 20 240
TOTAL 492

Total Storage Needed: 30 kb/hr

We need to integrate additional memory to store data. We would like to store for at least 2 days, requiring 1.4MB of memory.

What 3D-printable materials are available to use and meets requirements?

Material Properties
Nylon Strong, durable & flexible; 1mm minimum wall thickness; 10 layers/mm
ABS Strong; 1mm minimum wall thickness; 3 layers/mm; solvent weldable & smoothable
PLA Strong (less flexible than ABS); 1mm minimum wall thickness; 3 layers/mm
Ninjaflex/FilaFlex Rubber-like; no support; earbuds/exterior casing with no support features

Systems Architecture

A functional block diagram was developed in order to identify the function between input and output variables.

 Functional Block Diagram

Functional Block Diagram

Live Document Updated by Tegan Ayers

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 3, Team BASE hopes to accomplish the following tasks:

Home | Planning & Execution | Imagine RIT

Problem Definition | Systems Design | Preliminary Detailed Design | Detailed Design

Build & Test Prep | Subsystem Build & Test | Integrated System Build & Test | Customer Handoff & Final Project Documentation