Sanath

WIRELESS ELECTRONIC

STETHOSCOPE

BASED ON ZIGBEE

K SANATH KRISHNA HOLLA

4SF10EC041

1SCEM DEPT OF ECE 3/27/2014

•INTRODUCTION

•WORKING

•BLOCK DIAGRAM

•FUNCTIONS

•FEATURES

•APPLICATIONS

•ADVANTAGES

•DISADVANTAGES

•FUTURE ENHANCEMENTS

•CONCLUSION

•REFERENCES

CONTENTS


Introduction

• The Stethoscope is an acoustic medical device for

listening to internal sounds in human body which

is known, in medical terms, as auscultation.

• Heart sound auscultation is one of the most

basic ways to assess the state of the cardiac

function.

• The heart sounds and murmers are band limited

to about 100-1000Hz.


Working

• The electronic stethoscope is based on

embedded processor.

• The data can be transmitted through wireless

transmission using Zigbee module.

• A microphone is used to pick up the sound of

the heart beat.

• Acoustic stethoscope can be changed into a

digital stethoscope by inserting an electric

microphone into its head.


Working(cont..)

• Heart sounds are processed, sampled and sent

wirelessly using Zigbee module so that multiple doctors

can do auscultation.

• PC connectivity is provided through serial port where

from audio and video can be made available through

LAN and internet for telemedicine consultation.


BLOCK DIAGRAM

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Transmitter

SCEM DEPT OF ECE 3/27/2014

System design

• System design consists of two parts that is transmitter and

receiver.

• The transmitter system consists of the following hardware

components :

1) Front end circuitry – sensor, preamplifier, filter and power

amplifier with variable gain

2) microcontroller

3) zigbee module.


Frontend circuitry• Front end circuitry is signal acquisition and

preprocessing system .

• First part is a sensor that can be used in the chest

piece of an electronic stethoscope to convert body

sounds into an electronic signal

• Microphones are the common choice of sensor for

sound recording. The output of the microphone is fed

to signal pre-processing module.

• The role of signal pre-processing circuit is to adjust the

signal from sensor with a series of amplification and

filtering so that it meets the follow-up A/D sampling

demands and the signal-noise ratio is improved.


Fig4: Signal Pre-processing Circuit


Microcontroller

• The output of signal Pre-processing Circuit is

converted into digital form by ADC.

• 12 bit ADC of microcontroller is used. Here

PIC18f2423 microcontroller is used. Some

features are as follows:-

o 0-40 MHz Operating frequency

o 16 K bytes flash program memory

o 768 bytes data memory

o 12-bit ADC (10 input channels)

o Serial communication :- SSP and USART


Zigbee module

• For wireless transmission zigbee module JN5148 is

preferred.

• It is ultra low power, high performance device.

• It‟s operating frequency is 2.4GHz and data rate is 250

kbps


PC Connectivity

• Signal from system ( that is analog signal ) is given to

PC through input pin for storage purpose .

• The audio signal is stored in form of .wav file for further

analysis.

• The audio video interface is provided using web camera

through internet for proper positioning of stethoscope.

• The LAN support is also provided for the system using

JAVA


BLOCK DIAGRAM

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Receiver


System design

• The hardware design of receiver consists of zigbee

module, microcontroller, DAC, Power amplifier.

• Zigbee module captures the signal in the air and

transmits to microcontroller.

• The received signal is in digital form ,hence we have to

first convert it into analog.

• The signal from microcontroller is given to 12 bit digital

to analog converter.


Cont…

• Here PIC16f873 microcontroller is used.

• Signal from microcontroller is given to 12 bit DAC

MCP4822.

• The MCP4822 devices are designed to interface directly

with the Serial Peripheral Interface (SPI) port available

on many microcontrollers.

• Then this analog signal is amplified by power amplifier

with gain control same as at transmitter side


Features

• Low level heart and lung sounds are amplified

with clear audibility so that in noisy area also

proper auscultation is possible.

• Noise reduction takes place by filter that‟s why

accuracy increases.

• There is gain control facility provided by power

amplifier and frequency selection facility provided

by filter design.


Continued..

• Heart sound can be stored on PC and accessed through

internet to consult with other physician.

• Using Zigbee, wireless auscultation is possible and

patient can be monitored by multiple physicians at a

time.


Applications

• Can be used to continuous monitor aged people

• For patients having heart diseases

• For initial test of typhoid

• Check and monitor fever and infection related diseases


Advantages

• It can amplify the sound in a noisy environment.

• Most electronic stethoscopes have a microphone in the

head that projects sound, earphones to higher volume.

• Can be used as a wireless or recording device.


Disadvantages

• The electronic stethoscope requires batteries, and

these batteries may die some time unexpectedly.

• Their might be error at the receiver due to the overflow

at the receiver.


Future enhancements

• Improve detection of errors.

• Add battery status.

• Include overflow control.


Conclusion

• It is possible to record and visualize the signal

successfully. Moreover, the validation of the signal is

done.

• Heart beat signals are sensed, sent, displayed,

monitored, stored, reviewed and analysed with ease.

• It will help to improve the accuracy of the

cardiovascular diseases diagnosis.


References

1) Habit Wang, Jian Chen, Choi Samjin, “Heart Sound Measurement And

Analysis System with Digital Stethoscope”, International Conference on

Biomedical Engineering and Informatics, 2009.

2) Anh Dinh &Tao Wang, „Bandage-Size Non-ECG Heart Rate Monitor Using

ZigBee Wireless Link‟, International Conference On Bioinformatics and

Biomedical Technology (ICBBT) ,Page 160-163, 2010.

3) Yang Tang ; Guitao Cao; Hao Li; Kanjie Zhu “The Design of Electronic

Heart Sound Stethoscope Based on Bluetooth”, 2010 4th International

Conference on Bioinformatics and Biomedical Engineering (iCBBE) Digital

Object Identifier: 10.1109/ICBBE.2010.5516342 Publication Year: 2010 ,

Page(s): 1 - 4 Cited by: page 1

4) Yi Luo, “Portable Bluetooth Visual Electrical Stethoscope Research”, 11th

International Conference on Communication Technology Proceeding (ICCTP)

2008.


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THANK YOU


COMPONENT

SPECIFICATIONS

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[1] Sensor (condenser microphone)

Sensitivity: -44± 3dB -46± 3dB

Frequency: 20-16000Hz

Max operation voltage: 10.0V

Standard operation: 2.0V

Current consumption: Max 0.5mA


Condenser microphone

•Condenser Microphone, is a parallel plate capacitor and

works on the principle of a variable capacitance.

• It consists of two plates, one fixed (called the back

plate) and the other moveable (called Diaphragm) with a

small gap between them.

• An electric potential charges the plate. When sound

strikes the diaphragm it starts moving,

thereby changing

the capacitance between the

plates which in turn results

in a variable electric current to flow.


COMPONENT

SPECIFICATIONS

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Preamplifier(LM741)

Supply voltage- 18V

Power dissipation- 500mw

Operating temp. range- 0~+70 C

Supply current- 1.5 to 2.8mA

Power consumption- 50 to 85mW


COMPONENT

SPECIFICATIONS

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Power amplifier(LM386)

Supply voltage- 22V

Power dissipation- 1.25W

Input voltage- ±0.4V

Operating temp. rang- 0˚C~+70˚C

Output power- 325mW


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Number of

Converters:

2

Resolution: 12 bit

Interface Type: SPI, Serial (3-

Wire, Microwire)

Number of DAC

Outputs:2

Supply Voltage -

Max:

5.5 V

Supply Voltage -

Min:

2.7 V

MCP4822


PIC microcontroller 8051 microcontroller

Based on RISC Based on CISC

Uses Harvard architecture Uses Von-Neumann architecture

Has built in A/D converter No A/D converter in it

Has about 35 to 75 instructions Has 250 instructions

Allows 12bit processing at a time. Allows 8bit processing at a time.


THE IEEE 802 WIRELESS SPACE

Data Rate (Mbps)

Ran

ge

ZigBee

802.15.4

15.4cWPAN

WLAN

WMAN

WWAN

WiFi

802.11

0.01 0.1 1 10 100 1000

Bluetooth

802.15.1


Why zigbee over Bluetooth?

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Parameter Bluetooth Zigbee

Range Up to 10metres 1.5 to 2km

Frequency band 2.4 to 2.485 GHz 2.4 GHz

Power consumption High Very low

Topology Star Mesh, tree, star, cluster

Complexity High Low

Device types Mobile Stationary

Application Industrial control and monitoring building automation, home control and automation

Wireless connectivity between devices such as phones, laptops


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1. Zigbee aims at automation whereas

Bluetooth aims at connectivity of mobile

devices in close proximity.

2. Zigbee uses low data rates, low power

consumption on small packet devices while

blue tooth uses higher data rates, higher

power consumption on large packet devices.

3. Zigbee networks support longer range

devices and more in number compared to

Bluetooth networks whose range is small.

4. Given Zigbee‟s almost instant network join

times(30 milliseconds) its more suitable for

critical applications while Bluetooth‟s longer

join time is detrimental (3 seconds).


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Acoustic Electronic

Sound of heart beat cannot

be heard in a noisy

environment.

It can amplify the sound in a

noisy environment.

Consists of a chest piece

,hollow tube and the ear

buds.

Most electric

stethoscopes have a

microphone in the head that

projects sound, earphones to

higher volume.

Can be used just as a normal

stethoscope.

Can be used as a wireless or

recording device.

Diaphragm-200Hz to 600Hz(

used for lung sounds)

Bell-20Hz to 550Hz(used for

heart sounds)

Frequency range-16Hz to

20KHz


SSP DEFINES HOW TO SET UP VIRTUAL SERIAL PORTS

AND CONNECT TWO BLUETOOTH ENABLED

DEVICES.USAGE SCENARIOS

A SCENARIO WOULD BE USING TWO DEVICES, SUCH

AS PCS OR LAPTOPS, AS VIRTUAL SERIAL PORTS AND

THEN CONNECTING THE TWO DEVICES

VIA BLUETOOTH TECHNOLOGY.

• The full range of human hearing extends from 20-

20000 hz. The accepted frequency range of human

heart sounds is about 20-200hz and the accepted

frequency range of human lung sounds is about

25-1500hz.

• Diaphragm material polyurethane-coated silicone


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• Technical parameters

• Typical joining a networkÂ using Bluetooth takes three

seconds while for ZigBee it is 30 milliseconds.

• Depending on radio class, Bluetooth has a network

range of 1 to 100 meters while Zigbee is up to 70 meters

with a maximum network speed of 1M bit per second to

250 M bit per second respectively.

• Bluetooth has a protocol stack size of 250 Kilo bytes

and 28K bytes for Zigbee.

• Batteries for blue tooth devices are rechargeable

whereas for Zigbee they are not re chargeable but longer

lasting.

• Bluetooth is a protocol known for exchanging almost all

types of data such as text, multimedia. On the contrast,

Zigbee protocol is precisely for operational instructions

and not much variety of data is known to be exchanged

using it.


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For prototype we would like to check for three

conditions

• Valve diseases

• Arrhythmia

• Typhoid


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Valve diseases

In adults, abnormal heart murmurs most often are

caused by acquired heart valve disease.

A heart murmur is an extra or unusual sound

heard during a heartbeat. Murmurs range from

very faint to very loud.

Normal heartbeats make a "lub-DUPP" or "lub-

DUB" sound. Doctors can hear these sounds and

heart murmurs using a stethoscope.


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Arrhythmia

An arrhythmia (ah-RITH-me-ah) is a problem

with the rate or rhythm of the heartbeat.

During an arrhythmia, the heart can beat too

fast, too slow, or with an irregular rhythm.

A heartbeat that is too fast is called

tachycardia (TAK-ih-KAR-de-ah). A heartbeat

that is too slow is called bradycardia (bray-

de-KAR-de-ah).


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Typhoid

Initial stages of typhoid can be detected using this

device

During typhoid the pulse rate increases by 10 for

every degree increase in body temperature

So when ever this condition occurs an alarm will

be sent to the concern person


•The LM386 is a power amplifier designed for use in low voltage consumer applications.

The gain is internally set to 20 to keep external part count low, but the addition of an

external resistor and capacitor between pins 1 and 8 will increase the gain to any value

from 20 to 200. The inputs are ground referenced while the output automatically biases to

one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating

from a 6 volt supply, making the LM386 ideal for battery operation.

• Pins 1 and 8 control gain. When not connected (NC), the amplifier gain is 20. Adding a

10uF capacitor between them gives a gain of 200. Intermediate values are also possible,

as described in the datasheet.

• Pins 2 is the negative input – GND in our case.

• Pin 3 is the positive input – i.e. the actual signal to be amplified. There is a 10K

potentiometer before it, which adjusts the input signal level, acting as a volume control.

• Pins 4 (GND) and 6 (Vs) provide the supply voltage for the amplification. For this setup a

4x AA NiMh battery pack is used, which provides ~5V.

• Pin 5 is the output. It is biased to 1/2 of the supply voltage Vs. In simple terms, this

means that the signal there has two components: An AC component, which is the

amplified input signal, plus a DC component of 1/2 Vs = 2.5V. This biased voltage

cannot be fed directly to a speaker, but is exactly what we need for a μC sound sensor.

The 250uF electrolytic capacitor filters out the DC component and the remaining AC

goes to the speaker.

• The 0.05uF capacitor and 10 ohm resistor pair from pin 5 to ground turns out to be

called a“Boucherot cell” or “Zobel Network” and is used to prevent high frequency

oscillations.

3/27/2014 SCEM DEPT OF ECE 44

http://en.wikipedia.org/wiki/Boucherot_cell



http://en.wikipedia.org/wiki/Zobel_network




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