Electrocardiograph (ECG) Demonstration Board · Develop an ECG demonstration board for the...
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Electrocardiograph (ECG) Demonstration Board 6/3/2013 Design Team 3 1 Team Members Justin Bohr Xie He Yuan Mei Chaoli Ang Nate Kesto Mike Mock Sponsor Peter Semig Texas Instruments – Precision Analog Facilitator Professor Ramakrishna Mukkamala
Transcript of Electrocardiograph (ECG) Demonstration Board · Develop an ECG demonstration board for the...
Electrocardiograph (ECG)
Demonstration Board
6/3/2013 Design Team 3 1
Team Members Justin Bohr
Xie He Yuan Mei
Chaoli Ang Nate Kesto Mike Mock
Sponsor Peter Semig
Texas Instruments – Precision Analog
Facilitator Professor Ramakrishna Mukkamala
Project Background
Develop an ECG demonstration board for the Precision Analog group at Texas Instruments.
TI intends to showcase their integrated circuit (IC) performance using the demonstration board. Provides TI with customer interest in specific precision analog components.
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Definition of Success
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Expectations Functionality
Professional Display
Process signals from CardioSim II (simulator)
Display ECG output signal with Stellaris EVB Oscilloscope
Include TI components in design
Project Objective Develop several iterations of analog front-end (AFE)
circuits to interface a cardio simulator with an oscilloscope
Simulate, build, and test to optimize a final design
Development Strategy
Research ECG Systems
Software and Simulations
Breadboard Testing
Develop AFE Printed Circuit Board
Measure System Performance
Optimize Design
Develop Final Solution
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Research
Studied ECG systems to observe functionality
ECG signals
Noise Artifact Mitigation
Battery-Powered Applications
Observations
Bandwidth: 0.7 – 100 Hz
Amplitude: 1.0mVpp – 1.5mVpp
Active and passive filtering
Linear dropout regulator or Buck converter (9V to 5V)
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TI Components
Final Texas Instrument Circuit Components
• Instrumentation Amplifier – INA333
• Operational Amplifier – OPA378
• Linear Drop-Out Regulator (LDO) – TPS7A4201
• Buck Converter – TPS62120
OPA378 INA333 TPS7A4201
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ECG System Structure
Vre
f
VCC
VCC
Vref
VCC
VC
C
RG1 10k
RG2 10k
R3 10k
R5 1M
NS
NS1 2.5
R14 1
M
NS
NS2 2.5R7 1k
C4 47n
R4 1k
C2 47n
R8 63.4k R9 63.4k
C5 3
3p
C6 3
3p
R10 63.4k R11 63.4k
C7 3
3pC8 3
3p
C9 3
30p
+
-
+
U2 OPA333
+
-
+
U4 OPA333
R16 1
M
RG
+
-V-
RefOut
V+RG
U3 INA333
+Vin
C1 1
T
VF
VoA
Vin
L2 1T
R12 1
MC10 1u
+
-
+
U1 OPA333
NS
NS3 2.5
R15 1M
R13 1
M
V3 0
V4 0
R17 100k
R1 100k
R2 100k
ECG Signal
Input LP Filter
Instrumentation Amplifier
Output LP Filter
Stellaris μC Display
Right Leg Drive
Servo HP Filter
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Simulation Results
DC Servo loop attenuates low frequency wandering below 0.7 Hz
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Breadboard Testing
Using adapters for INA333 and OPA333
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Phase 1
Analog Front End Circuit (AFE)
Printed Circuit Board (PCB) Layout
Buck Converter Reference Design (TPS62120)
Test Points & Jumpers
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Phase 1 Results
PCB layout error
Successful operation
Buck converter measurements
Phase 1 AFE output using CardioSim II
40.00
45.00
50.00
55.00
60.00
65.00
0.09 0.9 9 90
Ga
in (
dB
)
Frequency (Hz)
Measured Bode Plot of System Bandwidth
Bandwidth: 0.7 Hz – 23 Hz Passband Gain: 64 dB
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Phase 1 Results
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Phase 2
Fixed PCB trace error
Battery Connector
Thumb Pad Test
LDO vs. Buck Converter Comparison
RLD switch
Increased System Bandwidth to 50 Hz
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Phase 2 Results
Successful implementation of thumb pad sensors
Power circuit comparison
Increase bandwidth to 50 Hz for more ECG spectral content
TPS7A4201 TPS62120
Input Voltage (V) 9.5 9.5
Input Current (mA) 0.74 0.43
Input Power (mW) 7.03 4.08
Output Voltage (V) 4.93 5.12
Output Current (mA) 0.67 0.71
Output Power (W) 3.30 3.63
Efficiency (%) 47.00 88.98
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Phase 2 Results
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Phase 3
LDO for Power solution
Thumb pads orientation
Organized layout
Selectable bandwidth 50 Hz or 100Hz
Created holes for board mounting
Battery on bottom of board
LED power indicator 6/3/2013 16 Design Team 3
Phase 3 Results
Selectable output filters
Labeled sub-circuits for demonstration purposes
Battery life of 211 hrs
Optimized thumb pad position
Improved connections for inputs and outputs
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Phase 3 Results
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Acrylic Display
Mount AFE on standoffs
Display Stellaris at 45 degrees
SolidWorks 3D model
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Code Modifications
Larger timebase options including 100 ms/div and above
Smoother screen updating
Default settings changed for optimized ECG viewing
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Demonstration
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Future Design Improvements
Implement a FFT for digital filtering on the Stellaris
Calculate BPM from FFT and display on LCD screen
Design the analog system using higher-order filters
Integrating Stellaris display board and AFE board into one PCB
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Questions?
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