An Overview Of Sa Node Controls Engineering Essay

An Overview Of Sa Node Controls Engineering Essay

SA node controls the rate of Black Marias muscular contractions which enables the bosom to go around the blood throughout the organic structure harmonizing to the demand. Small fluctuations in the bosom round are non harmful but in some instances due to misfunctioning of the bosom ‘s electrical system, the bosom rate varies drastically ensuing in different types of arrhythmias. These cardiac arrhythmias are serious upsets which should be treated instantly. Arrhythmias like bradycardia ( low bosom rate ) can be treated utilizing Pacemakers. Pacesetters can be implanted in the patient ‘s bosom for for good exciting the bosom. It is used for patients for whom the SA node is no longer working decently. External Pacesetters are besides available which is used to handle impermanent bosom rate fluctuations. It is used for a short period of clip before the engrafting the Internal Pacemakers in the bosom. In order to understand the demand of pacesetters, it is necessary to understand the operation of the bosom and its electrical system.


Heart is a pumping device which is used to go around the blood throughout the organic structure. It has four Chamberss viz. Right Atrium, Left Atrium, Right Ventricle and Left Ventricle. The right atrium receives the deoxygenated blood from the full organic structure through the superior vein cava and inferior vein cava. The left atrium receives oxygenated blood from the lungs through the pneumonic venas. When the atrium contracts the blood flows to the corresponding ventricle. This is due to atrial depolarisation. When the left ventricle contracts, the oxygenated blood is supplied to all tissues in the organic structure through the aorta. This is due to ventricular depolarisation. Similarly, the deoxygenated blood is pumped to the lungs for oxygenation through the pneumonic arteria during the contraction of right ventricle. This is due to ventricular repolarization.

The Electrical conductivity system of the bosom consists of SA node, AV node, Bundle of His, Purkinje Fibers. The Chamberss of the bosom should be stimulated electrically for contraction. The stimulations are provided by the SA node ( Natural Pacemaker of the bosom ) which is located in the right atrium of the bosom near the entryway of the superior vein cava. Although all the bosom cells have the ability to bring forth electrical pulsations which can excite the bosom, SA node triggers the bosom. The fact that SA node produces pulsations at a higher rate when compared to other possible cells which can excite contraction, contributes to this phenomena. The contraction of assorted Chamberss of the bosom is characterized in a really specific mode. As the electric pulsations pass through each chamber of the bosom, they are stimulated to contract. The SA node first triggers the right and left atrium to contract. Then the urges travel to the AV node which is located between the atria and the ventricles. From AV node, the pulsations travel to the package of his. The pulsations travel to the single ventricles through the right and left bundle subdivision and make the Purkinje fibres. If the SA node fails, so the AV node Acts of the Apostless as the primary pacesetter. If the AV node fails, so the Purkinje fibres takes the duty. The SA node receives blood supply from right and left coronary arterias. Under ischemic conditions, the decease of the affected cells will halt the SA node from triping the bosom round.

There is a period of clip following the stimulation of bosom musculus during which no other action potency can trip the bosom muscles. This period is known as Absolute or Effective Refractory Period ( ERP ) of bosom. It is usually around 0.4 sec. ERP is maintained every bit high as possible in order to keep tachycardia and to organize the musculus contraction. The anti-arrhythmic drugs taken by the patients normally prolongs the ERP.

Figure: 1 – Electrical SYSTEM OF HEART


The electrical activity of the bosom muscles is recorded as Electrocardiogram ( ECG ) . It can be acquired non-invasively from the surface of the organic structure by following specific lead constellations. The electrical current generated in the bosom due to depolarisation and repolarization is spread non merely within the bosom but besides throughout the organic structure. So, ECG can be easy acquired from the surface of the organic structure through electrodes. ECG has four basic constituents viz. , P wave, QRS composite, T moving ridge and U wave. P wave occurs during atrial contraction due to atrial depolarisation. The continuance of the P wave scopes from 0.08- 0.1 sec. During the atrial depolarisation, the urge from the SA node spreads throughout the atrium. The clip period between the oncoming of the P moving ridge and the beginning of the QRS composite is about 0.12- 0.2 sec. During the zero possible period between the P moving ridge and QRS composite, the impulse travels within the AV node and the Bundle of His.QRS complex occurs during ventricular contraction due to ventricular depolarisation. The continuance of the QRS complex scopes from 0.06-0.1 sec. T wave occurs during ventricular relaxation due to ventricular repolarization. Sometimes, a little positive U moving ridge occurs following the T moving ridge due to the last leftovers of the ventricular repolarization.



3.1.1. Normal Electrocardiogram:

Figure: 3 – Convention ECG

Heart rateis the figure ofheartbeatsper unit oftimewhich is expressed as beats per minute ( beats per minute ) . Heart Rate varies as the organic structure ‘s demand for O alterations, such as duringexercise or slumber. The measuring of bosom rate is carried bymedical professionalsto aid in thediagnosisand trailing of medical conditions. It is besides used by persons, such asathletes, who are interested in supervising their bosom rate to derive maximal efficiency from their preparation.

TheR waveto R moving ridge interval ( RR interval ) is the opposite of the bosom rate. Typical healthy resting bosom rate in grownups is 60-80 beats per minute which is referred to be normal bosom rate, with rates below 60 beats per minute referred to asbradycardia and rates above 100 beats per minute referred to astachycardia. But, jocks have resting bosom rate in the scope 45-50 beats per minute.

3.1.2. Missed Electrocardiogram:

Figure: 4 -MISSED ECG

This can be detected when the R-R interval is twice the existent R-R interval ( for normal topics ) .Heart pulses girls at some intervals and does non follow the premature bosom round.

3.1.3. Bradychardia:

Figure: 5 – Bradycardia

This is a critical decrease of bosom rate and characterized by usually directed abnormally broad P moving ridges and normal PR interval. Whenever the R-R interval exceeds 1 sec the bosom rate goes below 60 and the status is referred to as Bradychardia. There are three types of Bradychardia conditions based on the features of the ECG moving ridge, they are Sinus bradychardia, Atrio-ventricular nodal bradychardia and ventricular bradychardia severally. They are discussed below.

3.1.4. Sinus bradycardia:

Figure: 6 – Fistula BRADYCARDIA

Sinus bradycardias are besides called as Atrial bradychardias. This bradychardia status is normally found in immature and healthy grownups. The symptoms represent with the individual’srespirations. Inspiration causes lessening in the bosom ‘s rate of contraction.Expirationcauses an addition in the bosom ‘s rate of contraction. This is thought to be caused by alterations in the pneumogastric tone duringrespiration.

Sinus bradycardia is a sinus beat of less than 60 beats per minute. It is a common status found in both healthy persons and those who are considered wellconditioned jocks. The ground for this is that their bosom musculus has become conditioned to hold a higher shot volume and therefore requires fewer contractions to go around the same volume of blood.

Sick fistula syndromecovers conditions that include terrible sinus bradycardia, sinoatrial block, fistula apprehension, and bradycardi-tachycardia syndrome ( atrial fibrillation, waver, and paroxysmal supraventricular tachycardia ) .

3.1.5. Atrio ventricular nodal bradycardia:


An atrio ventricular nodal bradycardia or AV junction beat is normally caused by the absence of the electrical urge from thesinus node. This normally appear on anEKGwith a normal QRS complexaccompanied with an upside-down P wave either before, during, or after the QRS composite.

An AV junctional flight is a delayed pulse arising from anectopicfocus someplace in theAV junction. It occurs when the rate ofdepolarizationof the SA node falls below the rate of the AV node.This dysrhythmia besides may happen when the electrical urges from the SA node fail to make the AV node because of SA or AV block.This is a protective mechanism for the bosom, to counterbalance for a SA node that is no longer managing the gait devising activity, and is one of a series of backup sites that can take over pacesetter map when the SA node fails to make so. This would show with a longerPR interval. A junctional flight composite is a normal response that may ensue from inordinate pneumogastric tone on the SA node. Pathological causes include sinus bradycardia, fistula apprehension, fistula issue block, or AV block.

3.1.6. Ventricular bradycardia:


This image shows an ECG of a individual with an unnatural beat ( arrhythmia ) called an atrioventricular ( AV ) block. P waves show that the top of the bosom received electrical activity. Each P moving ridge is normally followed by the tall ( QRS ) waves. QRS waves reflect the electrical activity that causes the bosom to contract. When a P moving ridge is present and non followed by a QRS moving ridge ( and bosom contraction ) , there is an auriculoventricular block, and a really slow pulsation ( bradycardia ) .


More than 60 % people fall victim to bosom onslaughts in most of the states around the Earth every twelvemonth and 1000s more are critically injured in accidents. Taking attention of these patients in particular attention units involves the use of specialised equipments like pacesetters along the other of import 1s.

In the past few old ages electronic pacesetter systems have become the of import 1 in salvaging lives of cardiac patients whose normal pacing maps have been impaired. Depending on the exact nature of a cardiac disfunction, a patient may necessitate impermanent unreal tempo during the class of intervention or lasting tempo in order to take an active, productive life after intervention.

A device capable of bring forthing unreal tempo urges and presenting them to the bosom is known as a pacesetter system ( normally called a pacesetter ) and consists of a pulse generator and appropriate electrodes. Pacesetters are available in a assortment of signifiers. They are chiefly divided into two types External pacesetters and Internal pacesetters severally.

4.1. External Pacesetter:

For patients with impermanent bosom jobs such as those encountered in the coronary patients, external pacesetters are used. It is besides used when the SA node is found to excite the bosom at a lower rate. They are besides used for impermanent direction of certain arrhythmias that occur in the patients during critical postoperative periods and in the patients during cardiac surgery, particularly if the surgery involves the values or septum. An external pacesetter normally consists of an externally worn pulse generator connected to electrodes located on or within the myocardium. External pacesetters, which include all types of pulse generators located outside the organic structure, are usually connected through wires introduced into the right ventricle via a catheter. The pulse generator may be strapped to the lower arm of a patient who is confined to bed, or worn at the middle of an ambulatory patient.

Depending on the manner of operation, there are two types of pacesetter as listed below

  1. Asynchronous pacesetter & A ;
  2. Synchronous pacesetter

4.1.1. Asynchronous Pacesetter:

This type of pacesetter is intended for patients holding lasting bosom blocks. The rate is preset. It can be varied externally within the scope of 60 PPM to 180 PPM. Since this pacesetter functions irrespective of the patient ‘s natural bosom beat it poses a possible danger because of competition between the patient ‘s beat and that of the pacesetter.


4.1.2. Synchronous Pacesetter:

In patients who have normal bosom map most of the clip, asynchronous tempo can be highly unsafe, working against their ain physiological pacesetter with the danger of exciting in the vulnerable period of the T moving ridge, a status that can ensue in fibrillation. The demand pacesetter consists of an ECG amplifier and a conventional pacesetter end product pulse circuit that has been modified to let end product from the ECG amplifier to suppress the pulsation generator. This pacesetter senses R-waves and its timing and logic circuits count out an elapsed clip interval following an R-wave or antecedently induced pulsation. If the intrinsic R-wave does non look before the elapsed clip interval, the ventricle is stimulated. If an R-wave is received, the counter is reset once more. This type of pacesetter is used for patients with bradycardia, and it ensures a pulse no slower than its set rate.

Figure: 10 – Tempo Pulsation FROM SYNCHRONOUS PACEMAKER

4.2. INTERNAL Pacesetter:

Internal pacesetter are implanted within the pulse generator placed in a surgically formed pocket below the right or left collarbone, in the left subcostal country, or in adult females, beneath the left or right major pectoral muscles musculus. Internal leads connect to electrodes that straight contact the interior of the right ventricle or the surface of the myocardium. The exact location of the pulse generator depends chiefly on the type of the electrode used, he nature of the cardiac disfunction, and the method ( manner ) of pacing that may be prescribed.Since there are no external connexions for using power, the pulse generator must be wholly self contained, with a power beginning capable of continuously runing the unit for a period of old ages.


A broad assortment of electrodes can be used to mensurate bio electric events but about all can be classified as belonging to one of three basic types ;

  1. Micro electrodes
  2. Skin surface electrodes
  3. Needle electrodes

All three types of bio potency electrodes have the metal-electrolyte interface. In each instance, an electrode potency is developed across the interface, relative to the exchange of ions to the metal and the electrolytes of the organic structure.


They are used to mensurate bio electric potencies near or within a individual cell.Microelectrodes are electrodes with tips sufficiently little to perforate a individual cell in order to obtain readings from within the cell. The tip must be little plenty to allow incursion without damaging the cell. This action is normally complicated by the trouble of accurately positioning an electrode with regard to a cell. Because of their little surface country, they have electric resistances good up into the megohms. For this ground, amplifiers with highly high electric resistances are required to avoid lading the circuit and to minimise the effects of little alterations in interface electric resistance.


Skin surface electrodes are used to obtain bio electric potencies from the surface of the organic structure. They are available in assorted size. Although any type of surface electrode can be used to feel ECG, EMG, EEG potencies, the larger electrodes are normally associated with ECG, since localisation of the measuring is non of import. Smaller electrodes are used in EEG and EMG measurings. Assorted types of disposable electrodes have been introduced in recent old ages to extinguish the demand for cleansing and attention after each usage. In general, disposable electrodes are of the drifting type with simple snap connections by which the leads, which are reclaimable, are attached. Although, some disposable electrodes can be reused several times, their cost is normally low plenty that cleaning for reuse is non warranted. They come pre gelled, ready for immediate usage.


To cut down interface electric resistance and, accordingly, motion artefacts, some electroencephalographers use little subdermal acerate leafs to perforate the scalp for EEG measurings. They are besides used to mensurate EMG potencies from a specific group of musculuss. They are less susceptible to motion artefacts when compared with surface electrodes as they create an interface beneath the surface of the tegument. By doing direct contact with the subdermal tissue or the intercellular fluids, these electrodes besides seem to hold lower electric resistances than surface electrodes of comparable interface country. Even though needle electrodes have less gesture artefacts, surface electrodes are used to get ECG because surface electrodes are more convenient for the patient.Most of the surface electrodes are inexpensive and reclaimable.


ECG detectors measure the time-varying magnitude of electric Fieldss emanating from the bosom. ECG values are measured by puting non-invasive electrodes at the surface of the patient ‘s tegument. For a 3-lead ECG detector, the electrodes need to be placed in a trigon ( Einthoven Triangle ) on the patient ‘s thorax as shown in the figure 11. Each corner of the trigon corresponds to one of the limbs: left manus, right manus, left pes. With the bipolar system, one limb is connected to the positive terminus of the amplifier and another limb to its negative terminus. Three limbs ( right arm-RA, left arm-LA and left leg/foot-LL ) are used. The right leg was used as “ Earth ” , to minimise intervention.

Figure: 11 – Einthoven TRIANGLE

We have the undermentioned bipolar leads:

  • Lead I: RA ( – ) to LA ( + )
  • Lead II: RA ( – ) to LL ( + )
  • Lead III: LA ( – ) to LL ( + )

We have taken the signal across RA and LA ( LEAD I ) and given it as input to the amplifier.


Bioelectric signals have really high input electric resistance. To halt the signal fading, we use Instrumentation Amplifier ( AD 624 ) which besides has high input electric resistance. It should hold high addition and low end product electric resistance.In order to take the common manner signals, it should hold a high Common Mode Rejection Ratio ( CMRR of approximately 90 dubnium ) .The possible at the surface of the organic structure ranges from 0 – 10 millivolts so the amplifier should hold high addition ( 1000 ) . We use a differential amplifier to magnify the bioelectric signals that occur as a possible difference between two electrodes, the bioelectric signals are applied between the inverting and non-inverting inputs of the amplifier. The signal is hence amplified by the differential addition of the amplifier. For the intervention signal, nevertheless, both inputs appear as though they were connected together to a common input beginning. Therefore, the common manner intervention signal is amplified merely by the much smaller common manner addition. The electrode impedances organize a electromotive force splitter with the input electric resistance of the differential amplifier. If the electrode electric resistances are non indistinguishable, the intervention signals at the inverting and non-inverting inputs of the differential amplifier may be different, and the coveted grade of cancellation does non take topographic point. Because, the electrode electric resistances can ne’er be made precisely equal, the high common manner rejection ratio of a differential amplifier can merely be realized if the amplifier has an input impedance much higher than the electric resistance of the electrodes to which it is connected. There are different lead constellations such as 3-Lead, 5-Lead, 12-Lead for geting ECG Signal. We have used 3-Lead system Lead – I Configuration.


Figure: 13 – Amplifier End product


LabVIEW( short for Laboratory Virtual Instrumentation Engineering Workbench ) is a platform and development environment for Visual Programming Language from National Instruments. LabVIEW is a graphical scheduling environment used by 1000000s of applied scientists and scientists to develop sophisticated measuring, trial, and control systems utilizing intuitive graphical icons and wires that resemble a flow chart.

LabVIEW offers unrivaled integrating with 1000s of hardware devices and provides 100s of constitutional libraries for advanced analysis and informations visual image. The LabVIEW platform is scalable across multiple marks and runing systems. LABVIEW is a GUI ( Graphical User Interface ) which can be used for processing of signals, images and other signifiers of informations. One of the most powerful characteristics LabVIEW offers applied scientists and scientists is its graphical scheduling environment.

With LabVIEW, one can plan custom practical instruments by making a graphical user interface on the computing machine screen through which one can:

  • Operate the instrumentality plan
  • Control selected hardware
  • Analyze acquired informations
  • Display consequences

One can custom-make front panels with boss, buttons, dials, and graphs to emulate control panels of traditional instruments, create custom trial panels, or visually stand for the control and operation of procedures. The similarity between standard flow charts and graphical plans shortens the acquisition curve associated with traditional, text-based linguistic communications.

The behaviour of the practical instruments can be determined by linking icons together to make block diagrams, which are natural design notations for scientists and applied scientists. With graphical scheduling, one can develop systems more quickly than with conventional scheduling linguistic communications, while retaining the power and flexibleness needed to make a assortment of applications.

We have used Lab position to get the signal, filtering and make other processing of the ECG signal. The existent clip signal is given into every bit input to ELVIS I which acts as the DAQ ( informations acquisition system ) .The block diagram of the Lab position execution is as shown in figure 14.



  • The ECG signal from the amplifier ( utilizing AD 624 ) is given as input to DAQ for geting the signal in Lab position package.
  • FFT of the ECG signal is obtained and viewed. We can see the frequence content of the ECG signal from the FFT obtained. WE can besides see the presence of 50 Hz power line intervention in the FFT of natural ECG.
  • A Smoothing filter with following specifications – Traveling norm, Rectangular filter with a half breadth of 20 is constructed. The Smoothed ECG is viewed. Smoothing Filter is used to take noise and 50 Hz power line intervention.
  • The Smoothened signal is given as input to the Butterworth Band Pass Filter of order 2 and a low cutoff frequence of 5Hz and high cut off frequence of 15Hz.Band Pass Filter is used to divide the QRS composite from the ECG Signal.
  • The end product of the Band Pass Filter is differentiated and squared inorder to heighten the QRS composite from the staying part of the wave form.
  • The bosom rate is calculated utilizing timing and tone measuring block. The block gives the frequence of repeat of the QRS composite. The frequence value is converted into clip value by taking opposite of it. Heart rate is calculated as follows.

    Heart Rate = 60/R-R Interval


    R-R Interval = 760ms

    Heart Rate = 60/760ms

    = 78.94 Beat generations /Minute

  • If the deliberate bosom rate is below the normal value, so pacing pulsations are produced.This is done by utilizing a instance construction.
  • The instance construction turns on merely when the instance is true ( Heart Rate is below normal value ) .Inside the instance construction we have a square moving ridge generator. The end product of the square moving ridge generator is differentiated and squared. We get a pulsation as a consequence of these operations.
  • The rate and amplitude at which the pulsations are produced can be modified easy at tally clip utilizing controls.
  • Whenever the bosom rate is normal, False status is selected.
  • For false status, we set the amplitude and frequence of the square moving ridge as nothing so that the pacesetter is switched off.
  • The Pacing Pulses generated can besides be taken out as an parallel electromotive force from the ELVIS and can be viewed in a DSO. Merely voltages in the scope +10 Vs to -10 Vs can be taken out from LABVIEW through ELVIS.



We have implemented the instance construction and other blocks by analyzing the general tutorials given in LV BASICS 1 MANUAL and LABVIEWBASICSII_85_ENG CLAD.




The amplifier which is used in package execution ( AD 624 ) is besides used here. It is followed by a filter. The amplifier end product is about 550 millivolt. A Filter is a circuit that is defined to go through a specified set of frequences while rarefying all signals outside this set. Filter webs may be either active or inactive. Passive filter webs contain merely resistances, inductances and capacitances. Active filters employ transistors or op As plus resistances, inductances and capacitances. Inductors are frequently used in active filters, because they are bulky and dearly-won and may hold big internal resistive constituents. Band Pass Filters pass merely a set of frequences while rarefying all frequences outside the set. A simple high base on balls filter followed by a low base on balls filter will organize a set base on balls filter. We have used a set base on balls filter ( 0.5Hz – 40 Hz ) to take high frequence signals like EMG and low frequence constituents like Base Line Wandering and gesture artefacts. We have used a 2nd order Butterworth Filter with -40 db/decade roll-off.

For Low Pass Filter, we used 0.5 Hz as the cut off frequency.C1 is chosen as a convenient value between 100 pF and 0.1AµF.For High Pass Filter, we used 40 Hz as the cut off frequence. We have implemented a Band Pass Filter harmonizing to the design given in OPERATIONAL AMPLIFIERS AND LINEAR INTEGRATIONAL CIRCUITS.



A Notch Filter transmits frequences in the base on balls set and culls unsought frequences in the halt set. In applications where low degree signals must be amplified, there may be present one or more of an mixture of unwanted noise signals. Examples are 50, 60 0r 400 Hz frequences from power lines, 120 Hz rippling from full – moving ridge rectifiers, or even higher frequences from regulated exchanging – type power supplies or clock oscillators. If both signals and signal frequence noise constituent are passed through a notch filter, merely the desired signals will go out from the filter. The noise frequence is “ notched out ” . We have designed a active notch filter ( utilizing LM 324 ) to take 50 Hz Power Line Interference. The amplitude of the acquired ECG signal is about 1 – 2 V. We got noise – free ECG for existent clip signal acquisition as shown below.




In order to pull out the QRS Complex from the ECG signal obtained, we use a set base on balls filter with halfway frequence of 17 Hz and band breadth of 6 Hz. The QRS signal obtained from the set base on balls filter is rectified for comparing with the threshold electromotive force generated by the sensing circuit. The filtered and rectified ECG is stored on a capacitance. This filtered and rectified ECG is compared with the fraction of this electromotive force. Whenever a threshold electromotive force is exceeded, the QRS pulsation is detected. After the sensing of every QRS pulsation, the capacitance recharges to a new threshold value after every pulsation.

Figure: 21 – Circuit FOR QRS DETECTION


Monostable Multivibrator generates a individual end product pulse in response to an input signal. It is besides known as One Shot Multivibrator. The clip period of the end product pulsation depends merely on the external constituents ( resistances and capacitances ) connected to the op-amp. The continuance of the input triping pulsation can be longer or shorter than the expected pulsation. The continuance of the end product pulsation is represented by the T. Since T can be changed merely by altering the resistances and capacitances, the one shooting multivibrators can be considered as a pulsation stretcher. This is because the breadth of the pulsation can be longer than the input pulse. In a stable or standby province, the end product of the multivibrator is zero or low-level logic. The end product of the multivibrator is forced to travel high ( E?Vcc ) when an external trigger is given. The end product stays zero until the following triggering pulsation is given. Then the rhythm repeats. The monostable multivibrator has merely one stable province. Hence, the name monostable.

The QRS sensor gives a pulsation for QRS detected which is given as an input trigger for a monostable multivibrator. This monostable multivibrator is used to bring forth a positive pulsation ( amplitude – 5V ) of desired pulsation breadth for every input triping ( negative border triping ) from the QRS sensor. We had used 555 Timer as a monostable multivibrator.

Figure: 22-MULTIVIBRATOR End product

Therefore, the parallel subdivision of the undertaking gets over with multivibrator. The end product of the multivibrator is processed utilizing PIC18F 4550 Microcontroller. It marks the beginning of the accountant subdivision.


PIC is a household of Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1640 originally developed by General Instrument ‘s Microelectronics Division. The name PIC ab initio referred to “ Programmable Interface Controller ” , but shortly thenceforth was renamed “ Programmable Intelligent Computer ” .

Movies are popular with developers and hobbyists likewise due to their low cost, broad handiness, big user base, extended aggregation of application notes, handiness of low cost or free development tools, and consecutive scheduling ( and re-programming with brassy memory ) capableness.

10.1. PIC 18F4550

Like all Microchip PIC18 devices, PIC18F4550 household are available as both standard and low-tension devices. Standard devices with Enhanced Flash memory, designated with an “ F ” in the portion figure ( such as PIC18F4550 ) , accommodate an operating VDD scope of 4.2V to 5.5V.Low-voltage parts, designated by “ LF ” ( such as PIC18LF4550 ) , map over an drawn-out VDD scope of 2.0V to 5.5V.

Our undertaking uses a standard PIC 18F4550.Hence this microcontroller uses a brassy plan memory of 24K bytes.It is a 8-bit microcontroller and so they handle informations as 8-bit balls. Movies have a set of registries that function as general intent random-access memory. Particular purpose control registries for on-chip hardware resources are besides mapped into the information infinite. The addressability of memory varies depending on device series and in PIC 18F4550 external codification memory is straight addressable which is an exceeding characteristic compared to baseline and mid line nucleus devices.

Movies have a hardware call stack, which is used to salvage return references. The hardware stack is non package accessible on earlier devices, but this changed with the 18F4550 device. Hardware support for a general intent parametric quantity stack was missing in early series, but this greatly improved in the 18F4550, doing the this device architecture more friendly to high degree linguistic communication compilers.

10.1.1. Core characteristics

All of the devices in thePIC18F 455 series household integrate a scope of characteristics that can significantly cut down power ingestion during operation. Cardinal points include:

  • Alternate Run Modes:By timing the accountant from the Timer1 beginning or the internal oscillator block, power ingestion during code executing can be reduced by every bit much as 90 % .
  • Multiple Idle Modes:The accountant can besides run with its CPU nucleus disabled but the peripherals still active. In these provinces, power ingestion can be reduced even further, to every bit small as 4 % of normal operation demands.
  • On-the-Fly Mode Switch:The power managed manners are invoked by user codification during operation, leting the user to integrate power-saving thoughts into their application ‘s package design.
  • Low Consumption in Key Faculties:The power demands for both Timer1 and the Watchdog Timer are minimized.

PIC18F 4550 has enhanced brassy plan memory, high computational public presentation at an economical monetary value. These characteristics make these microcontrollers a logical pick for many high – public presentation, power sensitive applications. It has an in built parallel to digital convertor. We have used MP LAB IDE, which is really efficient Windowss compatible package to plan for PIC microcontrollers. It provides high degree flexibleness for programming. It contains everything a coder needs to compose, edit, compile, nexus and debug the microcontroller.



Each codification developed is tested utilizing PIC 18 Simulator IDE. The Simulator gives an first-class environment for the PIC microcontroller household. It gives all the needed installations to enable the system interior decorators to get down undertakings right from the abrasion and complete them with easiness and assurance.

Many external embedded buildind blocks can be simulated.Some of it ‘s characteristics are:

  1. 8 ten LED Board.
  2. Keyboard Matrix
  3. LCD Module
  4. Oscilloscope
  5. Signal Generator
  6. 7 Segment LED Display Panel

Figure: 24- PIC 18 SIMULATOR IDE

The Code is encrypted in the accountant utilizing PIC KIT 2. The cryptography for PIC microcontroller is similar to C scheduling.

The microcontroller is the existent pacesetter of the undertaking. We have used the microcontroller for bring forthing pacing pulsations in both synchronal and asynchronous manner.


In asynchronous pacesetter the tempo pulsations are produced at a preset rate, irrespective of the current bosom rate. We have produced pacing pulsations at three different rates ( 60, 70, 80 ) .The amplitude of the tempo pulsation can be adjusted from 0-5V utilizing a suited potentiometer.

Figure: 25-CONTROLLER OUTPUT FOR ASYNCHRONOUS MODE ( Pulse Rate 60, 70, 80 )

10.4. Synchronous MODE Operation:

In Synchronous manner operation, the Pacemaker produces the tempo pulses merely when the SA node fails to excite the bosom for a given period of clip. Once the SA node starts to excite the bosom usually, the operation of the synchronal pacesetter Michigans. The end product of the monostable multivibrator is given to the microcontroller. The monostable multivibrator produces positive pulsation for each ECG moving ridge.

The microcontroller is used to mensurate the clip interval between these pulsations. Once the clip interval between any two pulsations exceeds 1000 MS, the accountant is programmed to bring forth a stimulating pulsation. The Refractory period of the bosom muscles play a critical function here. If S A node produces a pulsation instantly after 1000msec, it will non be considered by the bosom as a stimulation because it falls within the Effective Refractive Period of the Heart. The Heart muscles respond to the stimulations merely if appears after the Effective Refractive Period say 400msec.The clip interval between two square pulsation is measured and is used for bosom rate computation.


The bosom rate is displayed utilizing a Seven Segment Display. The bosom rate value obtained is converted to a BCD value. This BCD value is tapped from a 8-bit port of the microcontroller. The seven section show is controlled by IC 4511.The BCD value obtained from the microcontroller is given as input to the IC 4511.We have used common cathode seven section shows. The end product of IC4511 to the corresponding BCD inputs is as shown in the tabular array below.



11. Decision:

12. Appendix:

12.1. PIN DIAGRAM AND THEIR Explanation:

AD 624:

LM 324:

2, 6, 10, 13 – Inverting Input signal Terminals

3, 5, 9, 12 – Non-inverting Input Terminals

1, 7, 8, 14 – End product Terminals

555 Timer:

Ninety-nine 4511:

Seven Segment Display:


The pin inside informations of PIC18F4550 are explained below in item.

This pin is used to wipe out the memory locations inside the PIC ( i.e. when we want to re-program it ) . In normal usage it is connected to the positive supply rail.


These are the supply pins VDD is the positive supply and VSS is negative supply, or 0v.The maximal supply electromotive force is 6V and minimal electromotive force is 2V.

OSC1/CLK1 and OSC2/CLK2:

These pins are where we connect an external clock, which is crystal oscillator so that the microcontroller has some sort of timing.


Depending on the device selected and characteristics enabled, there are up to five ports available. Some pins of the I/O ports are multiplexed with an alternate map from the peripheral characteristics on the device. In general, when a peripheral is enabled, that pin may non be used as a general intent I/O pin. Each port has three registries for its operation. These registries are:

  • TRIS registry ( data way registry )
  • PORT registry ( reads the degrees on the pins of the device )
  • LAT registry ( end product latch )

The Data Latch registry ( LATA ) is utile for readmodify- write operations on the value driven by the I/O pins.


Port A is an 8-bit broad, bi directional port. The corresponding informations way registry is TRISA. Puting a TRISA spot ( = 1 ) will do the corresponding PORTA pin an input ( i.e. , put the corresponding end product driver in a high-impedance manner ) . Uncluttering a TRISA spot ( = 0 ) will do the corresponding PORTA pin an end product ( i.e. , put the contents of the end product latch on the selected pin ) . Reading the PORTA registry reads the position of the pins ; composing to it will compose to the port latch.

The RA4 pin is multiplexed with the Timer0 faculty clock input to go the RA4/T0CKI pin. The RA6 pin is multiplexed with the chief oscillator pin ; it is enabled as an oscillator or I/O pin by the choice of the chief oscillator in Configuration Register 1H. When non used as a port pin, RA6 and its associated TRIS and LAT spots are read as ‘0 ‘ . RA4 is besides multiplexed with the USB faculty ; it serves as a receiving system input from an external USB transceiver.

Several PORTA pins are multiplexed with parallel inputs, the parallel VREF+ and VREF- inputs and the comparator electromotive force mention end product. The operation of pins RA5 and RA3: RA0 as A/D convertor inputs is selected by clearing/setting the control bits in the ADCON1 registry On a Power-on Reset, RA5 and RA3: RA0 are configured as parallel inputs and read as ‘0 ‘ . RA4 is configured as a digital input.


PORTB is an 8-bit broad, bidirectional port. The corresponding informations way registry is TRISB. Puting a TRISB spot ( = 1 ) will do the corresponding PORTB pin an input ( i.e. , put the corresponding end product driver in a high-impedance manner ) . Uncluttering a TRISB spot ( = 0 ) will do the corresponding PORTB pin an end product ( i.e. , put the contents of the end product latch on the selected pin ) .

Each of the PORTB pins has a weak internal pull-in. A individual control spot can turn on all the pull-in. This is performed by uncluttering spot, RBPU.

On a Power-on Reset, RB4: RB0 are configured as parallel inputs by default and read as ‘0 ‘ ; RB7: RB5 are configured as digital inputs. Four of the PORTB pins ( RB7: RB4 ) have an interruption- alteration characteristic. Merely pins configured as inputs can do this interrupt to happen. Any RB7: RB4 pin configured as an end product is excluded from the interruption- alteration comparing. Pins, RB2 and RB3, are multiplexed with the USB peripheral and serve as the differential signal end products for an external USB transceiver RB4 is multiplexed with CSSPP, the bit choice map for the Streaming Parallel Port


PORTC is a 7-bit broad, bidirectional port. The corresponding informations way registry is TRISC. Puting a TRISC spot ( = 1 ) will do the corresponding PORTC pin an input ( i.e. , put the corresponding end product driver in a high-impedance manner ) . Uncluttering a TRISC spot ( = 0 ) will do the corresponding PORTC pin an end product ( i.e. , put the contents of the end product latch on the selected pin ) . In PIC18F4550 device, the RC3 pin is non implemented.

PORTC is chiefly multiplexed with consecutive communicating faculties, including the EUSART, MSSP faculty and the USB faculty Pins RC4 and RC5 are multiplexed with the USB faculty.

Unlike other PORTC pins, RC4 and RC5 do non hold TRISC spots associated with them. As digital ports, they can merely work as digital inputs. When configured for USB operation, the informations way is determined by the constellation and position of the USB faculty at a given clip.

On a Power-on Reset, these pins, except RC4 and RC5, are configured as digital inputs. To utilize pins RC4 and RC5 as digital inputs, the USB faculty must be disabled.


PORTD is an 8-bit broad, bidirectional port. The corresponding informations way registry is TRISD. Puting a TRISD spot ( = 1 ) will do the corresponding PORTD pin an input ( i.e. , put the corresponding end product driver in a high-impedance manner ) . Uncluttering a TRISD spot ( = 0 ) will do the corresponding PORTD pin an end product ( i.e. , Put the contents of the end product latch on the selected pin ) .

Each of the PORTD pins has a weak internal pull-in. A individual control spot, RDPU ( PORTE & lt ; 7 & gt ; ) , can turn on all the pull-ins. PORTD can besides be configured as an 8-bit broad Streaming Parallel Port ( SPP )

12.2. Plan:

12.2.1. Code for Asynchronous Pacesetter:

# include & lt ; p18f4550.h & gt ;

# include & lt ; delays.h & gt ;

nothingness chief ( )


TRISB=0x00 ;

PORTB=0x00 ;

OSCCONbits.IRCF2=1 ;

OSCCONbits.IRCF1=1 ;

OSCCONbits.IRCF0=1 ;


while ( 1 )


PORTB=0x01 ;

Delay1KTCYx ( 20 ) ;

PORTB=0x00 ;

Delay10KTCYx ( 200 ) ;



12.2.2. Code for Synchronous Pacemaker and bosom rate:

# include & lt ; p18f4550.h & gt ;

# include & lt ; delays.h & gt ;

long int I, tungsten, J, HR ;

nothingness chief ( nothingness ) {

OSCCONbits.IRCF2=1 ;

OSCCONbits.IRCF1=1 ;

OSCCONbits.IRCF0=1 ;




while ( 1 ) {

if ( PORTBbits.RB7==0 )


for ( i=0 ; i & lt ; =130000 ; i++ )


if ( PORTBbits.RB7==1 )

interruption ;


j=i/100 ;

HR=60000/j ;

PORTD= ( HR/10 ) *6+HR ;




12.2.3. Explanation of Functions used:

Delay 10KTCYx ( unsigned char int ) ;

The missive ten in the map name above bases for ‘times ‘ or ‘multiplication ‘ . It is non to be replaced by a figure as done in other map names.

Unit of measurement is a 8 spot value in the scope ( 0,255 ) .Unit=0is tantamount to Unit =256.

TCY stands for ‘instruction rhythm ‘ . The internal frequence of PIC 18 F4550 is 8 MHz.

So TCY=4/8Aµs=0.5 Aµs


Delay 10KTCYx ( 200 ) ;

This statement gives a hold of 1000000 Aµs ( 10*1000*200*0.5 ) which is equal to one second.

13. Mentions:

  1. Leslie Cromwell, “ Biomedical Instrumentality and measuring ” , Prentice hall of India, New Delhi, 2007.
  2. Joseph J. Carr and John M. Brown, “ Introduction to Biomedical Equipment Technology ” , Pearson Education, 2004.
  3. John G. Webster, “ Medical Instrumentation Application and Design ” , John Wiley and boies, New York, 2004
  4. Principles of Biomedical Instrumentation and Measurement By Richard Aston
  5. Biomedical signal Analysis ( A Case Study Approach ) – Rangaraj.M.Rangayyan
  6. Digital Signal System-Level Design Using Lab VIEW BY Nasser kehtarnavaz and Namjin Kim
  7. LV Basics 1 Manual
  8. LabVIEWBasicsII_85_eng CLAD
  9. External Pacemaker- Jigar O Patel.
  10. Biomedical signal Analysis ( A Case Study Approach ) – Rangaraj. M. Rangayyan.
  11. Operational Amplifiers and Linear Integrational Circuits – Robert F. Coughlin & A ; Frederick F.Driscoll.
  12. Linear Integrated Circuits – Roy Chowdry.
  13. PIC Microcontrollers -Know it all Di Jasio, Wilmshrust, Ibrahim, Morton, Bates, J.Smith, D.W.Smith, Hellebeyck.
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