Walking Stick With Heart Attack Detection

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Walking Stick With Heart Attack Detection

• ECE 445 Helen Kim
  
• Spring 2005 Choon Lee
• Project 28

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Introduction

• Why did we choose this topic?
• Create an equipment to be used in everydays life
  for a medical purpose
• Obtain the basic idea from Wireless Heart Attack
  Detector with GPS of Fall 2004
• Most heart attack results from coronary artery
  disease (the restriction of blood flow to the
  heart) and it causes instant death of person
• ----The Center for Disease Control

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Why did we choose this topic? (continued)

• Help senior citizens who have health hazardous
  moment most often
• Use a walking stick as the medium asking for
  medical help as well as the main unit of
  detection

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Objective

• Goals of Design
• -The wireless heart attack detector captures
  abnormal heart beat signals.
• -The alert system on the walking stick warns the
  user to realize his health condition.
• -Bluetooth wireless emergency calling system
  calls for help at the moment of heart attack via
  mobile phone.

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Objective (continued)

• Benefits
• Electrocardiogram (ECG) signal transmitted
  wirelessly from the wrist to the main unit on the
  stick. This avoids the inconvenience of the
  attachment of the stick to the wrists.
• Automatic wireless emergency calling system via
  Bluetooth module
• Warning mode giving the users a chance to avoid
  the fatal moment actively

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Original Design Review

• Obtain ECG waveform from both wrists.
• Transmit ECG waveform wirelessly from wrist to a
  receiver on the stick.
• Microcontroller on the stick will run a heart
  attack algorithm to detect possible heart attack.
• Microcontroller will make the users cell phone
  to call 911 if heart attack detected.

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Block Diagram

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Components and Functions

• ECG Analog Circuitry
• to obtain analog ECG waveform from wrists
• 1. Unity-Gain Buffer.
• As Impedance Transformer. Skin impedance is high
  and Op-Amps input impedance is infinity.
• 2. Differential Amplifier.
• Taking the difference between two bio signals
  from both wrists and output the ECG waveform with
  desired gain.

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Components and Functions

• 3. Bandpass Filter
• Lower Cutoff Frequency 0.9 Hz
• Upper Cutoff Frequency -105 Hz
• - This filter removes noise outside the frequency
  range of ECG waveform.
• - Without the filter, no recognizable ECG was
  obtained during testing.

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Components and Functions

• PIC16F877 as A/D Converter and RS232
• 1. A/D Conversion
• Analog ECG signal will be digitized into 8
  bits (0 127).
• 2. RS232
• -Parallel bits of ECG digital data will be
  translated into serial bits for transmission.
• -It is a standard for serial binary data
  interchange between a DTE (Data terminal
  equipment) and DCE (Data communication equipment)

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Components and Functions

• HP-3 Transmitter
• 1. The RS232 output of PIC16F877 will be
• fed into the input of HP transmitter.
• All the above components, ECG analog
  circuitry, PIC16F877 and HP-3 Transmitter will be
  worn on a wrist.

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Schematics
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• The following components will be installed on
  the walking stick.
• 1. HP-3 Receiver
• 2. Javelin Stamp microcontroller
• 3. EB500 Bluetooth Module

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Components and Functions

• HP-3 Receiver
• 1. The receiver will receive digital ECG waveform
  from wrist.
• 2. The receiver will then feed the digital signal
  to Javelin microcontroller.

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Components and Functions

• Javelin Stamp Microcontroller
• 1. Microcontroller will run an algorithm through
  the ECG data to detect heart attack symptoms.

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Components and Functions

• 2. Heart Attack Algorithm
• - Symptoms of Heart Attack
• Weak Amplitude, Irregular Heart
  Pulse and Widened QRS Pulse.
• - Checking Amplitude
• -A baseline is set up by averaging all
  the data points.

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Components and Functions

• -Amplitude is considered weak if it is below
  50 of the baseline.
• -Checking Irregular Heart Beat
• - normal pulse rate is between 35bpm and
  200bpm
• - if pulse rate falls outside of this
  range, then heart attack symptom is
  detected.

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Components and Functions

• -Checking Widened QRS Pulse
• - Normal pulse width should be less than
  36ms.

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Components and Functions

• Alert Level
• - The failure of each of the three symptoms will
  raise the alert level.
• -The threshold of the alert level is set to 10.
• -If threshold is surpassed, emergency call will
  be activated.

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Components and Functions

• LEDs
• -Two LEDs will indicate the alert level.
• -First LED means low risk, which will be turned
  on for alert level between 4 and 6.
• -Second LED means high risk, for alert level
  between 7 and 9.

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Components and Functions

• EB500 Bluetooth Module
• -Javelin Stamp will send some commands to EB500
  to set up a connection between the bluetooth
  module and the cell phone.
• -Bluetooth communication is nothing than just a
  wireless serial cable after the connection is set
  up.

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Components and Functions

• AT commands
• -AT commands direct a phone to dial (D), answer
  (A) and hang up (H).
• -Every AT command starts with AT
  (Attention). This is the command line prefix.

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Components and Functions

• -AT commands to make 911 call
• ATD911 \r
• ATD2173335257 \r (Calling lab)

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Schematics
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Functional Testing

• A/D Testing by inputting a known voltage level
  and checking the corresponding digital value.
• 0.1V - 5
• 1.0V 50
• 2.0V 100
• 2.5V 125
• 8 bits can only go up to 127
• The highest peak of ECG waveform from analog
  circuitry will be amplified to only 2.0V

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Functional Testing

• Collecting ECG waveforms
• -ECG Samples of team members
• -Notice that the amplitude is between 127 and
• -127 for 8 bits A/D.

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More ECG Samples
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More ECG Samples
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Functional Testing

• Heart Attack Algorithm Testing
• One of the ECG samples shown was stored and was
  changed in terms of amplitude, rate and width.
• Javelin Stamp was modified to run with this
  modified data.
• Each of the three thresholds responded
  correspondingly.

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Functional Testing

• Bluetooth Communication Lab Call
• -The communication worked properly and the lab
  phone rang properly.

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Successes Challenges

• Challenges Before Successes
• Each component has to be tested and debugged
  individually before they were combined together.
• TTL logic signal of PIC were captured by scope to
  test the functionality.

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Successes Challenges

• - ECG waveforms were captured by Javelin Stamp to
  test the wireless communication between wrist and
  the stick.
• -Suitable bluetooth module was selected carefully
  by reading data sheets to check certain commands
  to make sure that it is connectable to a cell
  phone.

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Successes Challenges

• The notion of AT commands was obtained by surfing
  online technical forums.
• AT commands were given by somebody met at a
  technical forum.

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Test

• Operation Temperature
• We chose the reasonable range of outer weather.
• Test Range -25C to 50C inside freezer and by
  hair dryer
• Result We could observe that the whole system
  behaved properly.

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Test (continued)

• Transmitter / Receiver
• For our design, we assume the user stays the
  range of area near to the stick.
• Test range between wrist circuitry and the stick
  40 ft
• The javelin still could capture the digital
  signal.

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Recommendations

• Better biosensors that reduce noise when hands
  are moving.
• Better circuit design to reduce power
  consumption.
• Lighter material for the wrist circuitry and the
  main unit on the stick.