Traumatic Brain Injury
Eyewear “TB-Eye”
Todd Biesiadecki, Matthew Campbell,
Matthew Vildzius
ECE4007 L03 EM1
Advisor: Erick Maxwell
December 14, 2011
Overview
• 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 Objectives
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Lightweight, unobtrusive device
Battery powered
Data recording and storage
Wireless communication
Alert the user to get medical attention
Computer based graphical interface
Design Goals
Specification
Power Consumption
Supply Voltage
Battery Life
Battery Capacity
Weight
Size
Actual
61.67 mW
3.7 V
1 day of normal operation
400 mAh
50 g
Less than 4 x 0.6 x 0.2 inches L x
WxH
13.1mW
3.7 V
1 day of normal operation
110 mAh
14.5g/ 46.2g with glasses
3.4 x 0.7 x 0.35
1.45 x 0.5 x 0.22
Acceleration Range
Acceleration Recording
Threshold
Acceleration Alert Threshold
Sampling Rate (Idle)
±100g in all three axes
10g
±16g in all three axes
10g
50g
2 kHz
10g
3.2KHz
Sampling Rate (Active)
6 kHz
3.2KHz
Wireless Transmission Protocol
ANT+
Bluetooth
Transmission Power
Transmission Range
Data Storage
0 dBm
10m
Stores the value of acceleration
and time elapsed since the impact
occurred.
Displays the acceleration data
graphically
0 dBm
10m
Stores the value of
acceleration
GUI
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Target
Displays the acceleration data
graphically
Device mounted on a pair of sunglasses
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TB-Eye System-Level Diagram
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Device Operation
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Accelerometer
Measures
Motion
Above
Detection
Threshold?
MCU Sends
Data to
Transceiver
GUI
Requests
Data
Laptop
Receives and
Stores Data
MATLAB GUI
Reads Data File
for Display and
Analysis
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Yes
MCU
Increases
Sampling Rate
MCU Sends
Data to
Memory
Physical 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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Accelerometer
• 16G accelerometer
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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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Microcontroller
• 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 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 Flowchart
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Saving Serial Data
• Python script
– No standalone programs available
– Difficulties with serial functions in MATLAB
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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
Graphical User Interface (GUI)
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Integration 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 Mode
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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
Acceptance 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 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 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 Work
• Use ±100g accelerometer for full TBI detection
• Low cost size reduction:
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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
Questions?
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