portable heart rate monitor arrhythmia detector l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Portable Heart Rate Monitor & Arrhythmia Detector PowerPoint Presentation
Download Presentation
Portable Heart Rate Monitor & Arrhythmia Detector

Loading in 2 Seconds...

play fullscreen
1 / 35

Portable Heart Rate Monitor & Arrhythmia Detector - PowerPoint PPT Presentation


  • 616 Views
  • Uploaded on

Portable Heart Rate Monitor & Arrhythmia Detector. Enyinnaya Egejuru December 3, 2008 Senior Design Project. Instructor: Prof. Swenson. TA: Bob Schoonover. Section 1. Introduction . Objective.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Portable Heart Rate Monitor & Arrhythmia Detector' - paul


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
portable heart rate monitor arrhythmia detector

Portable Heart Rate Monitor & Arrhythmia Detector

EnyinnayaEgejuru

December 3, 2008

Senior Design Project

Instructor: Prof. Swenson

TA: Bob Schoonover

objective
Objective

Design a portable monitoring system able to acquire a biological signal (ECG) and detect abnormality from the regular sinus rhythm

  • Provide Immediate notification of abnormalities
  • Low cost and low power
  • Accessibility
  • User friendliness
project significance market
Project Significance/Market

This portable system will be useful whenever there is need for a low cost and low power monitoring system.

Possible markets:

  • Third world countries
          • Poor Medical Infrastructure, facilities and equipment
          • Unreliable power supply
  • Quick, portable monitoring
          • Warfront
the natural pacemaker
The Natural Pacemaker
  • The Sino-Atrial node (SA node) is a group of cells positioned on the wall of the right atrium
  • Cells in the SA node depolarize simultaneously resulting in contraction
  • Atrial contraction leads to the P-wave and the ventricular contraction leads to the QRS complex
block diagram
Block Diagram

MSP430FG4618

AD622

LM358

ALARM

electrodes signal acquisition
Electrodes (Signal Acquisition)
  • Interface between body and measuring/monitoring device.
  • Serve as transducer to change ionic current in body to electrical current
  • Electrolyte gel (AgCl) used to maintain good contact to skin
  • Pair used to measure potential difference between 2 parts of the body
ecg signal amplifier
ECG Signal Amplifier

AD622 Instrumentation amplifier chosen for initial signal amplification. Heart beat signal ranges from 1mV – 4mV, need amplification to about 1V

ecg signal amplifier cont d
ECG Signal Amplifier Cont’d
  • Gain of 10 from signal source, RG should be 5.62KΩ:
slide12

Biosignal from electrodes

Signal from Instrumentation Amplifier

analog filters
Analog Filters

Filters are used to attenuate certain frequencies

  • 0.05Hz High Pass Filter: Filters voltage drift to reduce baseline wander and amplifier saturation
  • 130Hz Low Pass Filter: Remove high frequency noise and muscle artifact

Cutoff Frequency determined by:

analog filters cont d
Analog Filters Cont’d
  • For High Pass: RC ≈ 3. Hence, Rhp = 100KΩ, Chp = 30µF
  • For Low Pass: RC ≈ .001. Hence, Rlp = 10KΩ Clp = 100pF
  • Further amplification (factor of 100) is done using a LM358 OP AMP
ecg signal after amplification
ECG Signal After Amplification

This signal shows a real BioSignal coming from a test subject

msp430fg4618
MSP430FG4618
  • Low supply-voltage range, 1.8V-3.6V
  • Ultralow power consumption
  • Five power saving modes
  • Wake up from standby mode in less than 6µs
  • 16 bit RISC architecture
  • 12 Bit A/D and 12 Bit D/A converters
  • 16 bit Timer_A
  • 116KB+256B Flash or ROM memory, 8KB RAM
msp430fg4618 mcu software
MSP430FG4618 MCU Software

The figure above is a block diagram showing the function of the MCU

digital filter design
Digital Filter Design

The MCU uses a high pass and a low pass filter

  • Fastest Deflection is the QRS complex. It lasts for about 20ms and has a frequency of 6Hz-30Hz
  • FIR filters were used because they are more stable
  • 17 tap FIR filter was implemented. Although higher taps would be better, we are working with limited resources
  • Filter design done using Matlab
digital low pass filter
Digital Low Pass Filter

This filter was built using the filterbuilder functionality of Matlab. Coefficients are determined and convolution is performed

digital high pass filter
Digital High Pass Filter

This filter was built using the filterbuilder functionality of Matlab. Coefficients are determined and convolution is performed

heart rate calculation
Heart Rate Calculation
  • Sample rate of 512 Hz. Allowing up to 10 samples or QRS complex.
  • Tracking of timescale using a variable (pulseperiod)
  • Output of QRS discriminator compared against threshold
  • Due to real-time need, pulseperiod is accumulated over 3 beats

Heartrate per minute = 1/[pulseperiod/(3 x 512 x 60)] = 92160/pulseperiod

notification
NOTIFICATION

The Winbond® ISD17120 ChipCorder® is a highquality, fully integrated, single-chip multimessage voice record and playback device Ideally suited to a variety of electronic systems

  • 120sec messages at 8Khz sampling frequency
  • PWM class D speaker driver
  • LED blinking notification during playback
  • Multiple message addressing
  • Playback enabled by signal from MCU
  • Great sound quality during voice playback using 54c6
ecg simulation
ECG Simulation
  • Was able to get ECG simulated WAV files
  • Testing of circuit for tachycardia and bradycardia could be easier as database has records of such arrhythmias
  • WAV files are transferred to circuit via a modified speaker phone. The right and left ear pieces correspond to the right arm and left arm
lcd heart rate display
LCD Heart Rate Display
  • New feature added to design
  • LCD displays a readable heartrate to user. This helped me in testing and figuring out what was going on in the MCU
other testing
Other Testing
  • Oscilloscope reading at each amplification stage
  • Setting test levels for tachycardia and bradycardia to check response of notification pin
  • Using an LED to tell when heartbeat has gone above or below normal
  • Artifact from movement and electrodes
successes
Successes
  • Adequately acquire Biosignal
  • Adequately amplify Biosignal
  • Proper ADC conversion
  • Semi Functional Heart Rate counter
  • Proper notification functionality
  • Adding new feature (LCD for rate display)
  • Using Low Power components for battery operation
  • Used a new device in ECE445 (MSP430) and also performed core functionality in MCU
  • Low power. System powered with a 3V battery (2x1.5)
challenges
Challenges
  • Sophisticated QRS/Thresholding algorithm with the amount of resources we have in a microcontroller
  • Poor Skin/Electrode interface
  • Artifact
  • Amplifier issues
          • Offset voltages
          • Open Lead wires
          • Electric field interference
recommendations
Recommendations
  • Digital 60Hz Notch Filter to reduce power line noise
  • A more sophisticated algorithm for QRS detection and heart rate calculation exists, but requires more resources (which will affect battery life) and is challenging to implement in a microcontroller
thanks to
Thanks to…
  • Dr. Gary Swenson Instructor
  • Bob Schoonover TA
  • Kenneth Gentry ECE415 Instructor
  • ECE Parts Shop personnel
  • ECE Stores personnel
  • Spencer Brady ECE420 TA
  • My Fellow ECE445-its