Optical Heart Monitor / Jump Drive Group 6

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Optical Heart Monitor / Jump DriveGroup 6

• Sponsor Calit2
• Mentor Paul Blair, Ph.D.
• Team Kari Nip, Matt Chandrangsu, Jeffrey Chi

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Agenda

• Design Specifications
• Weekly Progress
• Gantt Chart
• Questions

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Pulse Oximeter

• Typically a 2 LED system
• 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
• Only care about heart rate, not oxygenation
  levels.
• Still use a 2 LED device, as it is more readily
  available

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ADC Specs

• 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

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HR Circuitry OpAmp Specifications

• LM358 chip has two independent operational
  amplifiers on it
• 100dB voltage gain
• 3V 32V supply voltage range
• 2mV input offset voltage
• 1MHz bandwidth

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HR Circuitry Sensor

light
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HR Circuitry

• Received a commercial heart rate monitor PCB to
  investigate
• Compared PSPICE simulations to circuit data
• Familiarized with Eagle Layout editor

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HR Circuitry PSPICE Simulation
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HR Circuitry Circuit data
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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

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HR Circuitry Eagle layout
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HR Circuitry Plans

• Continue working with Eagle Layout editor
• Refine PCB layout
• Better component placement
• Shorter traces
• Use of vias to make PCB layout more concise

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Signal Filtering

• Input Signal and Matched Filter

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Signal Filtering

• Convolution of matched filter (f) and input
  signal (g)

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Signal Filtering Plans

• Make filtered function square wave signal
• Develop further understanding of Matlab functions
• Create filtering program in C

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File Allocation Table

• 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/doublesec
  onds)
• 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

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Interfacing with USB

• Completed code to control LEDs on development
  board with button presses.
• Currently researching USB storage code to find
  which functions to leverage.
• Upcoming Tasks
• First Going to merge LED control code with
  storage code.
• Second Implement button press controlled file
  modification

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Gantt Chart