Sanath

WIRELESS ELECTRONIC
STETHOSCOPE
BASED ON ZIGBEE
K SANATH KRISHNA HOLLA
4SF10EC041
1SCEM DEPT OF ECE3/27/2014

•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
6
Transmitter
SCEM DEPT OF ECE3/27/2014

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
13
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.

24
THANK YOU

COMPONENT
SPECIFICATIONS
27
[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
29
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
30
Power amplifier(LM386)
Supply voltage- 22V
Power dissipation- 1.25W
Input voltage- ±0.4V
Operating temp. rang- 0˚C~+70˚C
Output power- 325mW

31
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)
Range
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?
34
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

35
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).

36
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

38
• 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.

39
For prototype we would like to check for three
conditions
• Valve diseases
• Arrhythmia
• Typhoid

40
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.

41
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).

42
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

Sanath

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