Traumatic Brain Injury Eyewear “TB-Eye”

Traumatic Brain Injury Eyewear “TB-Eye”

Todd Biesiadecki, Matthew Campbell, Matthew Vildzius

ECE4007 L03 EM1Advisor: Erick Maxwell

December 14, 2011

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OverviewOverview

• Glasses to alert user of potential head injury• Approximately 50,000 people die and 85,000 suffer long

term injuries due to Traumatic Brain Injury(TBI) per year• For non-contact sports such as skiing and cycling

– Head impacts infrequent– specialized helmets not justified or practical

• Unit development cost: $234

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Design ObjectivesDesign Objectives

• Lightweight, unobtrusive device• Battery powered• Data recording and storage• Wireless communication• Alert the user to get medical attention• Computer based graphical interface

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Design GoalsDesign GoalsSpecification Target Actual

Power Consumption 61.67 mW  13.1mWSupply Voltage 3.7 V 3.7 VBattery Life 1 day of normal operation 1 day of normal operationBattery Capacity 400 mAh 110 mAhWeight 50 g  14.5g/ 46.2g with glassesSize Less than 4 x 0.6 x 0.2 inches L x

W x H3.4 x 0.7 x 0.351.45 x 0.5 x 0.22

Acceleration Range ±100g in all three axes ±16g in all three axesAcceleration Recording Threshold

10g 10g

Acceleration Alert Threshold 50g 10gSampling Rate (Idle) 2 kHz  3.2KHz

Sampling Rate (Active) 6 kHz  3.2KHz

Wireless Transmission Protocol ANT+ Bluetooth

Transmission Power 0 dBm  0 dBmTransmission Range 10m 10mData Storage Stores the value of acceleration

and time elapsed since the impact occurred.

Stores the value of acceleration

GUI Displays the acceleration data graphically

Displays the acceleration data graphically

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Device mounted on a pair of sunglassesDevice mounted on a pair of sunglasses

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TB-Eye System-Level DiagramTB-Eye System-Level Diagram

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Device OperationDevice Operation

Accelerometer Measures

Motion

Above Detection

Threshold?

MCU Increases

Sampling Rate

No

Yes

MCU Sends Data to Memory

GUI Requests

Data

Laptop Receives and Stores Data

MATLAB GUI Reads Data File for Display and

Analysis

MCU Sends Data to

Transceiver

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Physical DimensionsPhysical Dimensions

• Size:– Main Board: 3.4” long– Power Board: 1.45” long

• Weight: 14.5 g– With Glasses: 46.2 g

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AccelerometerAccelerometer

• 16G accelerometer – Analog Devices ADXL345– 145uA max. current– Measurements of 10G or more will trigger an alert– Utility of recorded data more limited vs. full range device

• Using built-in interrupts for threshold and data ready

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MicrocontrollerMicrocontroller

• ATMega328 microcontroller with Arduino libraries– Power consumption slightly higher than competition– Well-supported libraries

• Power consumption is 4mA while sampling

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Bluetooth TransceiverBluetooth Transceiver

• Acts as a cable replacement between device and computer

• Only sends data when requested by GUI• ANT wireless protocol difficult to work with, BLE not yet

available– Increased size– led to delay

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Microcontroller FlowchartMicrocontroller Flowchart

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Saving Serial DataSaving Serial Data

• Python script– No standalone programs available– Difficulties with serial functions in MATLAB

• Read binary data from the Bluetooth serial port• Format data as floating points in terms of g• Save data to a text file to be read by MATLAB• Called using the “Read Data From Device” button in GUI

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Graphical User Interface (GUI)Graphical User Interface (GUI)

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Integration with GlassesIntegration with Glasses

• Not allowed to modify given glasses for prototype• Prototype board is larger than desired• In production the circuit could be molded into the

glasses frame

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Battery Life in Monitoring ModeBattery Life in Monitoring Mode

• 110mAh battery• Microcontroller: 4mA max• Accelerometer: 0.15mA• Max current: 4.15mA• Worst-case battery life: 26 hours• Optimization could not be completed in time for demo• Slight additional power reduction should be possible• Notification LED adds additional 2mA• Peak of 45mA when Bluetooth is transmitting

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Acceptance TestingAcceptance Testing

• Device placed on simulated head• Impact head with calibrated amount of force

– Short impact similar to those expected to cause TBI• Used GUI to wirelessly receive, display data

– Compare measured data to calibrated impact • Demonstrated LED turns on when threshold is exceeded

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Prototype PCB problemsPrototype PCB problems

• Problems getting microcontroller to work (power, wrong frequency, wrong way of programming bootloader)

• Resolved with third microcontroller• Bluetooth must be temporarily disconnected for

programming

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Final BudgetFinal Budget

• Total budget: $405.00• Total spent: $234

– Expenditures:• Development: $69.85• Components for one board: $45.94 + PCB ($33) = $78.94• Unused parts: $85.21

– Spare capacitors, resistors, etc.– ANT modules– Alternate EEPROM module

• Oakley M-Frame MSRP: $129.00

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Future WorkFuture Work

• Use ±100g accelerometer for full TBI detection• Low cost size reduction:

– Use 4 or more layer board technology– Thinner PCB– Use 0402 and resistors and capacitors, QFN MCU– Eliminate headers, use smaller headers

• High cost: Custom integrated circuits• Better integration with glasses frame• Method to more securely attach to the head• Smartphone application

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Questions?Questions?