Download Optical Heart Monitor / Jump Drive - HEIG-VD

Optical Heart Monitor /
Jump Drive
Group 6
Sponsor: Calit2
Mentor: Paul Blair, Ph.D.
Team: Kari Nip, Matt Chandrangsu,
Jeffrey Chi
Agenda
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Design Specifications
Weekly Progress
Gantt Chart
Questions
Pulse Oximeter
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Typically a 2 LED system
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One red LED (660nm wavelength), one infared
LED (910nm).
Absorption of these wavelengths is different in
oxyhemoglobin and deoxygenated hemoglobin.
We only use 1 LED
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Only care about heart rate, not oxygenation
levels.
Still use a 2 LED device, as it is more readily
available
ADC Specs
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10 Bit resolution
65-260 µs Conversion Time
Up to 15 ksps at Maximum Resolution
Through Nyquist theory, the maximum signal
input frequency is 7.5 kHz
Input heart beat signal (approx. 60 Hz)
Previous data found at 250 sps
HR Circuitry: OpAmp Specifications
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LM358 chip – has two independent
operational amplifiers on it
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100dB voltage gain
3V – 32V supply voltage range
2mV input offset voltage
1MHz bandwidth
HR Circuitry: Sensor
light
HR Circuitry
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Received a commercial heart rate monitor
PCB to investigate
Compared PSPICE simulations to circuit data
Familiarized with Eagle Layout editor
HR Circuitry: PSPICE Simulation
HR Circuitry: Circuit data
HR Circuitry: Simulation vs. lab
At the maximum points of both output and
input signal:
Voltage gain (simulated) = 13.655
Voltage gain (circuit) = 9.337
HR Circuitry: Eagle layout
HR Circuitry: Plans
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Continue working with Eagle Layout editor
Refine PCB layout
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Better component placement
Shorter traces
Use of vias to make PCB layout more concise
Signal Filtering
Input Signal and Matched Filter
y  a1eb1 (t t1 )  a2eb2 (t t2 )
2
2
Signal Filtering
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Convolution of matched
filter (f) and input signal
(g)
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 f  g   n   f  m  g  n  m
m 
Signal Filtering: Plans
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Make filtered function square wave signal
Develop further understanding of Matlab
functions
Create filtering program in C
File Allocation Table
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0-10 File name (8 bytes) with extension (3 bytes)
11 Attribute - a bitvector. Bit 0: read only. Bit 1: hidden. Bit 2:
system file. Bit 3: volume label. Bit 4: subdirectory. Bit 5: archive.
Bits 6-7: unused.
12-21 Reserved (see below)
22-23 Time (5/6/5 bits, for hour/minutes/doubleseconds)
24-25 Date (7/4/5 bits, for year-since-1980/month/day)
26-27 Starting cluster (0 for an empty file)
28-31 Filesize in bytes
Interfacing with USB
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Completed code to control LED’s on
development board with button presses.
Currently researching USB storage code to
find which functions to leverage.
Upcoming Tasks:
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First: Going to merge LED control code with
storage code.
Second: Implement button press controlled file
modification
Gantt Chart