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HEART RATE MEASURMENT USING 8051 MICROCONTROLLER

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sai saketh

on 27 November 2014

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Transcript of HEART RATE MEASURMENT USING 8051 MICROCONTROLLER

HEART RATE MEASUREMENT USING 8051 MICRO CONTROLLER
PROJECT TEAM
PREOJECT MENTOR
Ms.K NAGA SAILAJA
TEAM MEMBER
Keerthana Reddy 12311A1917
Sai Saketh 12311A1954
B.Rajesh 13315A1902
ABSTRACT
The Project describes a technique of measuring the heart rate through a fingertip using a microcontroller. While the heart is beating, it is actually pumping blood throughout the body, and that makes the blood volume inside the finger artery to change. This fluctuation of blood can be detected through an optical sensing mechanism, consisting of a series of infrared light emitting diodes(IR LED) placed side by side.
The signal can be amplified further for the microcontroller to count the rate of fluctuation, which is the heart rate.IR LED transmits an infrared light into the fingertip, a part of which is reflected back from the blood inside the finger arteries. The photo diode senses the portion of the light that is reflected back. Every time the heart beats the amount of reflected infrared light changes, which can be detected by the photo diode. With a high gain amplifier, this amplitude change of the reflected light can be converted into a pulse.

WHAT IS A HEART RATE MONITOR?
A heart rate monitor is a personal monitoring device that allows a subject to measure their heart rate in real time or record their heart rate for later study.
This is widely used in various hospitals for checking the health of the patients.
WHY SHOULD WE MEASURE HEART RATE?
As heart rate represents how healthy the person is we know to regularly check the rate of functioning of heart.
Also,more than 2 million people are at a risk of heart attack.
It would be helpful if these people can check their heart rate easily.
INTRODUCTION
A heart rate monitor is a personal monitoring device that allows a subject to measure their heart rate in real time or record their heart rate for later study.
The sensor unit consists of an infrared light-emitting-diode (IR LED) and a photo diode, placed side by side, and the fingertip is placed over the sensor assembly .
The IR LED transmits an infrared light into the fingertip, a part of which is reflected back from the blood inside the finger arteries. The photo diode senses the portion of the light that is reflected back.
The intensity of reflected light depends upon the blood volume inside the fingertip. So, every time the heart beats the amount of reflected infrared light changes, which can be detected by the photo diode. With a high gain amplifier, this little alteration in the amplitude of the reflected light can be converted into a pulse.
LITERATURE REVIEW
MEATHODS USED TO FIND HEART RATE
1.Stethoscope - inaccurate

Advantages:
-simple way to measure the heart rate.
-Low cost.
-User friendly.
Disadvantages:
Major drawback of this method is,we may not hear the sounds correctly due to the clothing of the patient.


2.ECG(Electrocardiogram):
Advantages:
This method is sophisticated and gives accurate results.This method is performed for diagnostic or research purpose on heart.
Disadvantage:
1)very costly
2)causes discomfort to patients.
Because of the drawbacks which were observed in the above two methods,heart rate was measured using a micro controller.

MICRO CONTROLLER AND WHY NOT MICRPROCESSOR?

A microcontroller is a single-chip microcomputer which contains RAM , ROM , CPU , I/O ports , ADC and other peripherals.
It has fixed amount of RAM , ROM , I/O ports.
It is also called embedded microcontroller because it is designed for embedded systems performing specific tasks only.
Microprocessor only has CPU , ALU, stack pointer, program counter and other registers ,clock timing circuit.
Microprocessor does not have RAM, ROM and I/O ports
It requires large space and it’s cost is higher as compared to microcontroller.
PRINCIPLE
A heartbeat is a contraction of the heart's muscle, forcing blood to move through arteries and there by during contraction the blood in the finger artery will be relatively higher than in the expansion.
This change in blood flow is detected by the sensor assembly.
The photo current is converted into voltage and also amplified by transimpedance amplifier.
The processed signal from Amplification stage is fed into Micro Controller where the the number of pulses are counted from the signal and hence final output is displayed on the Seven Segmented display.
MAJOR COMPONENETS USED IN THE DEVICE
1.IR reciever and transmitter
2.Microcontroller
3.7-segment display unit
1.IR reciever and transmitter(LTH 1550-01)
A phototransistor is a light-sensitive transistor. A common type of phototransistor, called a photo bipolar transistor, is in essence a bipolar transistor encased in a transparent case so that light can reach the base–collector junction. The electrons that are generated by photons in the base–collector junction are injected into the base, and this photodiode current is amplified by the transistor's current gain β (or hfe). While phototransistors have a higher responsitivity for light they are not able to detect low levels of light .
2.Microcontroller AT8051
A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.

Features of AT8051
:
Compatible with MCS-51® Products
8K Bytes of In-System Programmable (ISP) Flash Memory
Endurance: 1000 Write/Erase Cycles
4.0V to 5.5V Operating Range
Fully Static Operation: 0 Hz to 33 MHz
Three-level Program Memory Lock
256 x 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Full Duplex UART Serial Channel
Low-power Idle and Power-down Modes
Interrupt Recovery from Power-down Mode
Watchdog Timer
Dual Data Pointer
Power-off Flag
3.7 segment display unit:
A seven-segment display (SSD), or seven-segment indicator, is a form of electronic display device for displaying decimal numerals
A seven segment display consists of seven LEDs arranged in the form of a squarish ’8′ slightly inclined to the right and a single LED as the dot character. Different characters can be displayed by selectively glowing the required LED segments.
Seven segment displays are of two types, common cathode and common anode. In common cathode type , the cathode of all LEDs are tied together to a single terminal which is usually labeled as ‘com‘ and the anode of all LEDs are left alone as individual pins labeled as a, b, c, d, e, f, g & h (or dot) . In common anode type, the anode of all LEDs are tied together as a single terminal and cathodes are left alone as individual pins.
CIRCUIT DIAGRAM
OUTPUT
The use of this device is very simple. Turn the power on. Place your forefinger tip on the sensor assembly, and press the start button.Do not move your fingure,you will see the LED blinking with heart beats, and after 15 sec, the result will be displayed.
1.PORTABLE:
The equipment is designed to be carried easily carried and used when required.
2.LOW POWER CONSUMPTION:
The components used in the circuit accept input voltage of 5V,so we can conclude that the equipment consumes less power.
3.ACCURATE MEASURMENT:
The circuit is equipped with RC components which reduce the disturbances in the circuitry.
4.FLEXIBILITY:
The microcontroller used in this equipment is ISP programmable. Also the opamp used does not depend on the quantity of the blood that flows.

ADVANTAGES
DISADVANTAGES
1.EXTERNAL DISTURBANCES:
As the sensor assembly is not closed, high intensity light sources can cause disturbances in the readings when the circuit is in operation.
2.COMPLEX:
Since the circuit is built on a vector board, many wires were used so if any fault occurs it would be difficult to identify the area where the defect has occurred.

FUTURE SCOPE
1.Heart rate monitoring in fitness centre.
2.For Athletes.
3.In Rural Areas where medical facilities are limited

REFERENCES
1. www.circuitstoday.com/heart-rate-monitor-using-8051
2. www.ti.com/lit/ds/symlink/lm124-n.pdf
3.http://www.atmel.com/images/doc2487.pdf
4. http://www.hobbyprojects.com/


PROCEDURE
The device senses the heart rate from the finger tip using IR reflection method and displays it on a three digit seven segment display in beats per minute.
The circuit has an accuracy of 4 beats per minute and it is very easy to use.
In medical terms, the technique used here for sensing heart rate is called photoplethysmography.
Photoplethysmography is the process of optically estimating the volumetric measurement of an organ.
When the heart expands (diastole) the volume of blood inside the finger tip increases and when the heart contracts (systole) the volume of blood inside the finger tip decreases.
The resultant pulsing of blood volume inside the finger tip is directly proportional to the heart rate and if you could some how count the number of pulses in one minute, that’s the heart rate in beats per minute (bpm).
For this an IR transmitter /receiver pair is placed in close contact to the finger tip.
When the heart beats, the volume of blood cells under the sensor increases and this reflects more IR waves to sensor and when there is no beat the intensity of the reflected beam decreases.
The pulsating reflection is converted to a suitable current or voltage pulse by the sensor.
The sensor output is processed by suitable electronic circuits to obtain a visible indication.
LTH1550-01 photo interruptor forms the photoplethysmographic sensor here.
LTH1550-01 is simply a IR diode – photo transistor pair in single package.
The front side of the IR diode and photo transistor are exposed and the remaining parts are well isolated.
When the finger tip is placed over the sensor the volumetric pulsing of the blood volume inside the finger tip due to heart beat varies the intensity of the reflected beam and this variation in intensity is according to the heart beat.
When more light falls on the photo transistor it conducts more, its collector current increases and so its collector voltage decreases.
When less light falls on the phototransistor it conducts less, its collector current decreases and so its collector voltage decreases.
This variation in the collector voltage will be proportional to the heart rate.
Any way this voltage variation is so feeble and additional signal conditioning stages are necessary to convert it into a microcontroller recognizable form.
The next part of the circuit consists of a two active low pass filters using opampLM324.
The LM324 is a quad opamp that can be operated from a single rail supply. Resistor R23, R17 and capacitor C5 sets the gain and cut off frequency of the first filter.
The second low pass filter also have the same parameters.
The two low pass filters form a very critical part of the circuit as any noise or false signals passing to the microcontroller stage will produce disastrous results.
The output of the filter stage will be a voltage level fluctuating between 0 and 0.35 volts and this fluctuation is converted into a 0 to 5V swing using the comparator based on the third opamp (IC1c).
The reference voltage of the comparator is set to 0.3V.
When ever the output voltage of the filter stage goes above 0.3V, the output of the comparator goes to zero and whenever the output voltage of the filter stage goes below 0.3V, the output of the comparator goes to positive saturation.
The result will be a neat pulse fluctuating between 0 and 5V at a rate equal to the heart rate.
This pulse is fed to the microcontroller for counting.
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