Taylor Holmes, Jason Partin, William Rody, Malcolm Stagg
Recap of Project
• A biometric device which functions as:
– Pedometer
– Calorie Counter
– Heart Rate Monitor
– Temperature Monitor
• Data will be used by students in a physics class
for calculating power and work
Objective Review
• Be able to measure and display heart rate
• Be able to measure and display temperature
• Be able to measure and display number of
steps taken
• Be able to calculate work done by user
• Implement green energy
Hardware
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Accelerometers (as a pedometer)
Pulse Sensor
Thermistors
Solar cells
Li-ion battery
Surface Mount Devices (SMDs)
• Super – tiny parts (0.3mm x 0.5mm)
• We will be soldering these to our PCB by
ourselves!
PCB Design
• 1.5” x 1.5” actual size
Original Design
PCB Changes
• Updated our schematic to correct some errors
and use an updated charge circuit
• Updated the PCB to pass the Design Rule
Check, which is required for fabrication
• “Metal pours” for lower ground resistance and
lower signal noise
• Improved parts placement
• Silkscreen labels for soldering
PCB Changes
• 1.5” x 1.5” actual size
Updated Design
(Submitted for Manufacture)
Coding
• To this point, we have:
– Found a library (FatFS) for creating a file system on
the flash memory
– Found TI USB interface libraries
– Found library code for Sharp Memory LCD
– Worked with TI Code Composer Studio to gain
familiarity with the tools
Enclosure Concept (from last semester)
Rough dimensional conjecture for the interior compartment
8 mm
Transparent lid
(acrylic or
transparent
polymer)
Enclosure Accomplishments
• 3D-Printed a prototype enclosure
• Used the Stratasys
Dimension Elite
(communication studio)
Enclosure Challenges
• We need more interior room,
but a less bulky enclosure!
• We’re currently working
on optimizing internal
real estate
• Also need to figure out
what went wrong with
the current printout
Pulse Sensor
• Low power optoisolator in a
small package
• Specs:
– Voltage = 3V to 5V
– Current = 4mA at 5V
Pulse Sensor
• LED illuminates the skin
• A phototransistor
senses the light’s
reflection
– Outputs an analog
waveform to the
microcontroller
(Taylor’s pulse from fingertip)
Pulse Sensor
• Additional challenges
– Filtering the signal
– Coding the GPIO pins of our microcontroller
Pedometer Objectives
• Count within ±1 step
for every 10 steps
taken
• Eliminate as many
“false steps” as
possible
Pedometer Progress and Goals
• Parts change (ADXL-345)
• Waiting on PCB to run tests
• Problem Identification
• Set On/Off Mode to help accuracy
• More useful for experimental purpose
Thermometer
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Measure skin temperature around the wrist
Measure before and after exercise
Uses 10k NTC Thermistor in voltage divider
3 Equations
𝑋
1023
∗ 3𝑉
– 𝑅𝑇 = 𝑅1
𝑉𝑖𝑛
𝑉𝑜𝑢𝑡
–𝑉=
1
𝑇
− 𝑅1
– = 𝐴 + 𝐵𝑙𝑛 𝑅𝑇 + 𝐶 ln 𝑅𝑇
3
Thermometer
• Testing hasn’t started yet
• Anticipate contact problem
• Adjustable Wrist Strap
Solar Cell
KXOB22-12X1
• 2 monocrystalline solar cells
• KXOB22-12X1 instead of KXOB22-01X8
• Why?
– Greater IV-Curve
– 18.6mW
– Isc = 50mA
LTC3105
Boost Converter
• Step up DC/DC converter
• Wide Vin range: 225mV to 5V
Voltage Regulator
TPS78330
• TPS78330 instead of the LTC3100
• Why?
– 5 pins (smaller & simple)
– Fixed Output (3V)
– Fewer Components
To Do List & Challenges
• Create an effective strap for the thermistor
• Integrate all the systems with the
microcontroller (Coding)
• Solder all systems and test them
• Create a smoother, more space-efficient
enclosure