Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 40 | Bilateral Earlobe Pulse Timing Measurement Device |
Joshua Joseph Mark Schmitt Zhikuan Zhang |
Shiyuan Duan | ||
| # Bilateral Earlobe Pulse Timing Measurement Device # Team Members Zhikuan Zhang (zhikuan2) Joshua Joseph (jgj3) Mark Schmitt (markfs2) # Problem Pulse transit time (PTT) is widely used as a non invasive indicator of cardiovascular dynamics but most existing systems measure PTT at a single peripheral location There is currently a lack of low cost synchronized hardware tools that enable bilateral pulse timing measurements such as comparing pulse arrival times between the left and right earlobes Without a dedicated time synchronized multi channel sensing platform it is difficult to study or validate whether body posture head orientation or environmental conditions introduce measurable bilateral timing differences This project addresses the need for a custom PCB based physiological sensing device that can reliably acquire synchronized ECG and bilateral PPG signals and serve as a general purpose measurement tool for this under studied topic # Solution This project proposes a PCB based multi channel physiological sensing system consisting of one ECG channel placed near the chest and two PPG channels placed on the left and right earlobes The system is designed as a measurement and validation tool rather than a research discovery platform The PCB focuses on low noise analog front end design precise time synchronization and multi channel data acquisition ECG R peaks are used as a timing reference and pulse arrival times from both PPG channels are compared under controlled conditions such as neutral posture head tilt or side lying # Solution Components ## Subsystem 1 ECG Analog Front End Function Acquire a clean ECG signal to provide a reliable cardiac timing reference Components Instrumentation amplifier such as AD8232 or equivalent ECG analog front end Analog high pass and low pass filtering stages Driven right leg circuit for common mode noise reduction Surface ECG electrodes Output Digitized ECG waveform with clearly detectable R peaks ## Subsystem 2 Dual PPG Sensing Channels Function Measure pulse waveforms at the left and right earlobes simultaneously Components Two identical PPG sensors such as MAX30102 or discrete LED and photodiode design Transimpedance amplifiers for photodiode current sensing Anti aliasing filters Optical shielding for ambient light rejection Output Two synchronized PPG waveforms suitable for pulse arrival time extraction ## Subsystem 3 Time Synchronized Data Acquisition and Control Function Ensure accurate relative timing between ECG and both PPG channels Design considerations All channels are sampled by a single microcontroller ADC or synchronized ADCs Shared clock source using a low ppm crystal oscillator Hardware level timestamping of samples Avoid reliance on BLE timing for synchronization BLE used only for data transfer if implemented Components Microcontroller such as STM32 or ESP32 Low drift crystal oscillator Shared sampling clock architecture # Criterion For Success Requirement 1 ECG signal acquisition Validation Clearly visible ECG waveform with identifiable R peaks Elevated heart rate observable after light exercise Requirement 2 PPG signal acquisition for both earlobes Validation Stable and repeatable PPG waveforms captured simultaneously from left and right earlobes Requirement 3 Channel time synchronization Validation Relative timing jitter between channels below predefined threshold such as less than 1 ms Consistent timing results across repeated measurements Requirement 4 Bilateral pulse timing comparison Validation ECG referenced pulse arrival times successfully computed for both earlobes under at least two different body conditions # Scope and Complexity Justification This project involves significant circuit level hardware design including low noise analog front ends synchronized multi channel data acquisition and mixed signal PCB integration The system complexity is appropriate for a senior design project and aligns with course expectations The project is inspired by experience working as a research assistant in a biological sensing laboratory and is positioned as a hardware measurement tool rather than a research discovery platform |
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