Development of Low Cost Microcontroller Based Spirometer

Development of Low live Microcontroller Based SpirometerSpirometer is an instrument which is apply to measure the chroma and capacity of lung. It collects the convey expired by the uncomplaining role to measure the lung spate or capacity. The spirometer has a device attached to it which pass on measure the movement of gas in and out of chest and this device is called as Spirograph. And in some spirometers spirographs ar replaced by printer called Spirogram. In most of the computerized administration the spirographs or the spirogram pass on display the predicted value next to the observed value.Using spirometer various tests are carried out to determine whether the enduring is having any respiratory disorder or not.Some of the tests carried out are-Tidal Volume (TV)-The amount of look that is breathed in and out by an indivi two-fold during normal respiration.Forced Vital message (FVC)-The amount of circularise that is maximally forced out of the lung after upper limi t inspiration.Forced Expiratory Volume In 1sec (FEV1)- The amount of port that commode be maximally forced out of the lung in the first secant of forced expiratory manuever.1.2 OBJECTIVE OF THE PROJECTTo design a rugged speak to microcontroller based spirometer and carry out the various lung functioning tests.To give way a program for the microcontroller to measure the lung volume and display the result digitally on a LCD interfaced with it.CHAPTER 2 LITERATURE SURVEYAUTHORSAgarwal.V ,Ramachandran N.C.S,2008,1TECHNIQUES utilizeThe patient exhales finished the mouth small-arm where the gas exchange is being acquired as the potency channelise by the transducer( sensing element).This signal from the sensing element is amplified by an instrumentality amplifier(INA 114).Then the amplified signal is filtered using a low-pass-filter which is so given up to a ADC(ADS7812) for digitisation.After digitisation it is given to the microcontroller(Intel) from which the data is displ ayed on the LCD screen.For provided interface for communication on internet ETHERNET device is used.RESULTSThe take emf from the amplifier is digitised using ADC which corresponds to the pressure contravention across mouth charm is computed by the microcontroller and displayed on the LCD screen.LIMITATIONS/FUTURE imaginativenessIn future the system is expect to be inexpensivemedical care for thousands of patient.AUTHORSNagaraja K.A,Nanda.S, 2007,2TECHNIQUES USEDThe patient exhales the air through the mouthpiece which consists of a melt sensor, differential pressure sensor, instrumentation amplifier,low pass filter and ADC.The flow sensor relates the velocity and the pressure of air short-winded if in that respect is no air flow through the sensor the velocity is switch overed to pressure and this pressure difference is sensed by the difference flow sensor which inturn provide the electrical quantity of the air flow.Inorder to remove noise and amplify the signal an instrume ntation amplifier is used.Which is then tack on to the band pass filter of the range 0.05Hz to 1.3Hz,where the spirometer lies in the range of 0.1Hz to 12Hz.The filtered signal is digitised using ADC and this data is read by a microcontroller which is then interfaced to a computer.RESULTSVarious tests are performed and FVC,FEV1 and their ratio are calculated and monitored.Depending on these set we determine whether its normal (or) restrictive (or) obstructive.LIMITATIONS/FUTURE massNot man-portableAUTHORSDr.David Van Sickle et.al ,2009,3TECHNIQUES USEDInitially the patient is allowed to expire through the spirometer.The spirometer consists of a pressure sensor(HW 24) which gives a DC voltage as output.This DC voltage is propotional to the pressure drop betwixt the leads which is recorded by the spirometer.This latitude data is then converted to digital using ZMD 31014 iLite chip.Microcontroller(PIC18f13k50) is used to convert the digital data to USB.Using mathematical algorit hm implemented in the computer it calculates the volume and displays on the screen.RESULTSGraphical display of flow vs volume is evaluated and monitored from which the following value can be calculated PEF,FVC, FEV(t) and FEV1/FVC ratio.LIMITATIONS/FUTURE VISION exceedingly expensive.AUTHORSOvlyaguli et.al,20014TECHNIQUES USEDThe test is performed using wedge bellow reference spirometer the FVC and FEV1 data collected are investigated where the test is performed on different patient and are grouped harmonizely.Then a mathematical modeling functioning is carried out based on stuporous value obtained from the flow graphs.These values for the subject with COPD is compared with healthy subject belonging to same age,sex and height.Then normalized for fuzzy labels Very low,low,Normal,High,Very Highwhich is the generated on rule base and simulated.RESULTSProvide the interrelationship between characteristic constants obtained from the curves and degree of indisposition and FEV1 values a re measured.LIMITATIONS/FUTURE VISIONIn future it eliminates the error factors and helps in accurate diagnosis.CHAPTER 3respiratory DISORDER SYMPTOMS CAUSES3.1 RESPIRATORY DISORDERRespiratory disorderdeals with the indispositionsof therespiratory system which include unsoundnesss of thelung,pleural cavity and bronchialtube. Respiratory diseases range from indulgent to life-threatening such asbacterial pneumoniaorpulmonary embolism which may lead to illness and death. The study of respiratory disease is cognise aspulmonology. A doctor who specializes in respiratory disease is know as a pulmonologist.Some of the common respiratory diseases are subversive lung disease.clogging lung disease.Restrictive lung disease.Pleural cavity diseases.3.2 OBSTRUCTIVE LUNG DISEASEObstructive lung diseasesare diseases of the lung in which thebronchialtubes become narrowed.COPDTwo examples for obstructive lung disease areChronic Obstructive Pulmonary Disease (COPD) is a disease in which the airway s become damaged and hence making them narrow. Asthma causes obstructor to the airflow out of the lungs.And the obstruction is reversible.3.2.1 SYMPTOMSPersistent cough.Sputumor mucous secretion production.Wheezing.Chest tightness.Tiredness.3.2.2 CAUSESSmoking.Occupational exposures.Air pollution.Genetics.Autoimmune disease.3.3 RESITRICTIVE LUNG DISEASERestrictive lung diseaseis also known asrestrictive ventilatory which restricts the lung expansion and there by decreases the lung volume and increases workof breathing.SYMPTOMSShortness of breath, cough3.3.2 CAUSESAsbestos is caused by semipermanent exposure to asbestos dust.Radiation fibrosis(radiation used for cancer treatment).Rheumatoid arthritis.3.4 DIAGNOSIS OF geometrical irregularity OF RESPIRATORY SYSTEM USING FEV1/FVC RATIOIn restrictive lung disease, some(prenominal)FEV1andFVCare lessen so theFEV1/FVC ratiois normal.In obstructive lung diseaseFEV1is reduced while theFVCis normal thus theFEV/FVC ratio is lowerCHAPTER 4 PRINCIPLE OF WORKINGThe spirometer consists of a turbine flow sensor containing LED( opening) on adept side and a photo-diode(detector) on the opposite side.Inbetween the LED and the detector there is a rotor.The rotor is a fan like structure with 3 fins.The above arrangement is present inside a cylindrical human face which is opened on both the sides.The LED and the photo-diode are molded with a light weight plastic design inside the case.A mouth piece is fitted on one side and the opposite side is kept open.When the patient blows air inside the mouth piece a pressure difference is created due to the atmospheric air(atmospheric pressure) that enters from the opposite side.A military force supply circuit is knowing to provide power supply to the spirometer.When the patient exhales through the mouth piece the rotor rotates.Whenever the rotor is in-between the source and the detector the light from the source is not detected by the detector and when the rotor is not in-between t hem then the light from the source is detected by the detector.Each rhythm leave be detected just now if 7ml of gas has been exhaled by the patient.These pulses are then given to the comparator which get outing give binary output only if the patient is exhaling.And when the patient is not exhaling there is no output from the comparator.This ouput is then given to a microcontroller which is programmed in such a way that it will ascertain the cast of pulses from the comparator and these pulses are converted into total number of rotations by dividing them(no of pulses) by 3(since the rotor has 3 fins).These rotations are then used to measure the lung volume.The lung volume is then displayed on a LCD which is interfaced with the microcontroller as digital output.CHAPTER 5SYSTEM DESCRIPTION5.1 ELECTRONIC lick5.1.1 POWER SUPPLY electric circuitA 12V and a 5V power supply circuit was implemented.5.1.1.1 IC 7812 IC 7805The two ICs are used to provide 12V and 5V supply respectively .12V from IC7812 is given to the turbine flow sensor.5V from IC7805 is given to LM324 Microcontroller.5.1.1.2 STEP-DOWN TRANSFORMERTransformer being used is a 230V-step down transformer.It converts AC to AC without any change in frequency.BRIDGE RECTIFIERThe diode used is IN4007 which acts as bridge rectifier and converts the given AC current to DC.5.1.2 SENSORThe sensor used here is FT-330 Turbine flow sensor.The input to the sensor is the air blown by the patient.5.1.2.1 FEATURESCan withstand temperature upto 80 degree celcius.Molded with electronics and a light weight plastic design.5.1.2.2 ADVANTAGESHighly accurate.Very compact.Reliable.5.1.2.3 POTENTIAL partition AND ZENER DIODEThe output of the turbine flow sensor is given to the potential drop sectionalization.The potential divider will reduce 12V from the turbine flow sensor and allows a reduced voltage to zener diode.The zener diode is used to fix a threshold i.e it allows only voltage inside 5V to the comparator.5.1.2. 4 COMPARATORLM324 acts as a comparator which gives a voltage within 5V(square wave) when the patient exhales through the sensor.And when the patient does not exhale, the comparator output shoot fors reduced to 0V.The output of the comparator is given to the microcontroller.5.1.2.4.1 FEATURESInternally frequency compensated for unity gain.Large DC voltage gain of 100 dB.Wide bandwidth (unity gain) 1 MHZ.Wide power supply rangeSingle supply 3V to 32Vor dual supplies 1.5V to 16V.5.1.2.4.2 ADVANTAGESEliminates need for dual supplies.Four internally compensated op amps in a single package. index number drain suitable for battery operation.5.1.3 MICROCONTROLLERThe microcontroller used here is 16F877A.The microcontroller receives input from LM324.The microcontroller is programmed in such a way that it will moot the number of pulses from the comparator and these pulses are converted into total number of rotations by dividing them(no of pulses) by 3(since the rotor has 3 fins).These rotati ons are then used to measure the lung volume(TV,FVC,FEV1).5.1.3.1 FEATURESRAM=368 bytesEEPROM=256bytesPROGRAM remembering=8Kilo bytesI/O downslopeS=335.1.3.2 ADVANTAGESThis IC can be reprogrammed and erased up to 10,000 times.It is very cheap. It can also be very easily assembled. spare components needed to make this IC work is a 5V power supply , 20MHz crystal oscillator and two 22pF capacitors.5.1.3.3 LCD DISPLAYThe output(TV,FVC,FEV1)from the microcontroller is displayed on the LCD according to the program.5.2 MECHNICAL DESIGN( MATERIALS USED)5.2.1.TURBINE FLOW SENSOR5.2.1.1 MODELFT-330 Turbine flow sensor5.2.1.2 ADVANTAGEHighly accurate, compact and reliable.5.2.1.3 FEATURESCan withstand temperature upto 80 degree celcius.Molded with electronics and a light weight plastic design.5.2.2. MOUTH PIECEMade up of plastic with a diameter of 2cm.CHAPTER 6CIRCUIT DESCRIPTION6.1 OVERVIEW OF CIRCUIT WORKINGInitially the patient is allowed to blow through the sensor and the output voltage from the sensor is given as input to the potential divider circuit which limits the current to zener diode and which inturn reduces 12V supply from the potential divider o/p and allows only 5V to be given to the inverting terminal of LM324(comparator). reviewererence voltage is given to pin 3 which gets the feedback from LM324 output. Hence when the patient doesnt blow, a amply voltage is received by pin 2(inverting terminal) which is compared with the reference voltage and in this case the i/p voltage reference voltage and hence we get a low voltage(0V) at the output and no pulse is seen and when the patient blows, i/p voltage CHAPTER 7EXPERIMENTAL STUDY7.1 algorithmInitialize the count to 0.When the patient exhales, the number of pulses from LM324 will be counted i.e. the count gets incremented.This count is converted into rotations since the rotor has 3 fins, if we get 3 pulse, it is considered as 1 rotation. So by dividing the count by 3 we will get the total number of rotat ions.The LM324 will give 1 pulse only if 7 ml of gas is exhaled . So the total number of rotations is multiplied by 7 to obtain the lung volume.Initially the flag will be 0.When the patient exhales TV will be displayed.When the limit is through the flag will be 1.Now when the patient exhales FVC will be displayed.When the reset is done again the flag will be 2.Now when the patient exhales FEV1 will be displayed .Again when the reset is done and the patient exhales then TV will be displayed.7.2 INFERENCEThus the tests results obtained from the designed spirometer matches with the tests results obtained from the laboratory spirometer.Minor differences in the value is due to effect of surrounding environment and lamentable air.CHAPTER 8CONCLUSIONThe objective of the project was to design a low cost spirometer for the rural health care centers,private clinicians and primary function laboratories.In order to confirm the objective of our work, we compared the market set of currently a vailable spirometer(MIR SpiroDoc Spirometer),the starting price of which is around $1974.50.Thus the tests results of four subjects obtained from the designed spirometer was compared with the tests results obtained from HELIOS Pulmonary Function test.The values had some minor differences due to effect of surrounding environment and moving air.But they were of acceptable accuracy.Future work involves interfacing the device with PC and implementation of the product in Telemedicine application for distance monitoring of respiratory parameter.APPENDIX 11.1 PIN CONFIGURATION OF LM324(COMPARATOR)Fig 1.1 Refwww.voltage current.info1.2 PIN CONFIGURATION OF PIC16F877AFig 1.2 Refhttp//www.best-microcontroller-projects.com/schematic.drawing-program.html1.3 OVERVIEW OF PIC 16F877AFig 1.3 Refhttp//www.best-microcontroller-projects.com/schematic.drawing-program.html