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Cardiac Monitoring System - EKG

Cardiac Monitoring System - EKG

I have used a heartbeat sensor module which senses the heartbeat upon putting a finger on the sensor.

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About this project

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How to go about it:

Heart rate, temperature and blood pressure human are very important parameters of the human body. Doctors use various medical devices like thermometer to check body temperature, blood pressure monitor BP and EKG to check for heartbeat monitoring.

In this project, I built a  heart rate monitoring system, using Arduino, that counts heartbeats in a minute. The system starts  measure the heartbeat once the finger is placed on the sensor.

Working of this project is quite easy but a little calculation for calculating heart rate is required. There are several methods for calculating heart rate, but here we have read only ten pulses. Then we have calculated total heart beat in a minute by applying the below formula:

IBI = sampleCounter - lastBeatTime;
runningTotal /= 10; 
BPM = 60000/runningTotal (runningTotal the last pulse)

When first pulse comes, I start counter by using timer counter function in Arduino that is millis() ;. And take first pulse counter value form millis( );. Then we wait for ten pulses. After getting ten pulses we again take counter value in time2 and then we substract time1 from time2 to take original time taken by five pulses. And then divide this time by 10 times for getting single pulse time. Now we have time for single pulse and we can easily find the pulse in one minute, deviding 600000 ms(60s) by single pulse time.

I used a serial port to transmit the signal pulse in computers to draw electrocardiogram using the Processing language which is built on the Java programming language. With it you can create a user interface easily.

Code

Arduino-codeArduino
This is the code from Arduino and you have to uploaded on your Arduino device.
#include<LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

byte heart[8] = 
{
  0b00000,
  0b01010,
  0b11111,
  0b11111,
  0b11111,
  0b01110,
  0b00100,
  0b00000
};

//  VARIABLES
int pulsePin = 0;                 // Pulse Sensor purple wire connected to analog pin 0
int blinkPin = 13;                // pin to blink led at each beat

// these variables are volatile because they are used during the interrupt service routine!
volatile int BPM;                   // used to hold the pulse rate
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // holds the time between beats, the Inter-Beat Interval
volatile boolean Pulse = false;     // true when pulse wave is high, false when it's low
volatile boolean QS = false;        // becomes true when Arduoino finds a beat.


void setup(){
  pinMode(blinkPin,OUTPUT);         // pin that will blink to your heartbeat!
  Serial.begin(115200);             //The speed of communication
  interruptSetup();                 

  lcd.createChar(1, heart);
  lcd.begin(16,2);  
  lcd.print("Heart Beat ");
  lcd.write(1);
  lcd.setCursor(0,1);
  lcd.print("Monitering");
  pinMode(pulsePin, INPUT);
  delay(1000);
}



void loop(){
  sendDataToProcessing('S', Signal);     // send Processing the raw Pulse Sensor data
  if (QS == true){                       // Quantified Self flag is true when arduino finds a heartbeat
        sendDataToProcessing('B',BPM);   // send heart rate with a 'B' prefix
        QS = false;                      // reset the Quantified Self flag for next time                       
       }
        delay(20);  
}

void sendDataToProcessing(char symbol, int data ){
    Serial.print(symbol);                // symbol prefix tells Processing what type of data is coming
    Serial.println(data);                // the data to send culminating in a carriage return
  }

volatile int rate[10];                    // used to hold last ten IBI values
volatile unsigned long sampleCounter = 0;          // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;           // used to find the inter beat interval
volatile int P =512;                      // used to find peak in pulse wave
volatile int T = 512;                     // used to find trough in pulse wave
volatile int thresh = 512;                // used to find instant moment of heart beat
volatile int amp = 100;                   // used to hold amplitude of pulse waveform
volatile boolean firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = true;       // used to seed rate array so we startup with reasonable BPM


void interruptSetup(){     
  // Initializes Timer2 to throw an interrupt every 2mS.
  TCCR2A = 0x02;     // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
  TCCR2B = 0x06;     // DON'T FORCE COMPARE, 256 PRESCALER 
  OCR2A = 0X7C;      // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
  TIMSK2 = 0x02;     // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
  sei();             // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED      
} 


// THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE. 
// Timer 2 makes sure that we take a reading every 2 miliseconds
ISR(TIMER2_COMPA_vect){                         // triggered when Timer2 counts to 124
    cli();                                      // disable interrupts while we do this
    Signal = analogRead(pulsePin);              // read the Pulse Sensor 
    sampleCounter += 2;                         // keep track of the time in mS with this variable
    int N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

//  find the peak and trough of the pulse wave
    if(Signal < thresh && N > (IBI/5)*3){       // avoid dichrotic noise by waiting 3/5 of last IBI
        if (Signal < T){                        // T is the trough
            T = Signal;                         // keep track of lowest point in pulse wave 
         }
       }
      
    if(Signal > thresh && Signal > P){          // thresh condition helps avoid noise
        P = Signal;                             // P is the peak
       }                                        // keep track of highest point in pulse wave
    
  //  Cautare semnal de puls 
  // signal surges up in value every time there is a pulse
if (N > 250){                                   // avoid high frequency noise
  if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){        
    Pulse = true;                               // set the Pulse flag when we think there is a pulse
    digitalWrite(blinkPin,HIGH);                // turn on pin 13 LED
    IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
    lastBeatTime = sampleCounter;               // keep track of time for next pulse
         
         if(firstBeat){                         // if it's the first time we found a beat, if firstBeat == TRUE
             firstBeat = false;                 // clear firstBeat flag
             return;                            // IBI value is unreliable so discard it
            }   
         if(secondBeat){                        // if this is the second beat, if secondBeat == TRUE
            secondBeat = false;                 // clear secondBeat flag
               for(int i=0; i<=9; i++){         // seed the running total to get a realisitic BPM at startup
                    rate[i] = IBI;                      
                    }
            }
          
   // keep a running total of the last 10 IBI values
    word runningTotal = 0;                   // clear the runningTotal variable    

    for(int i=0; i<=8; i++){                // shift data in the rate array
          rate[i] = rate[i+1];              // and drop the oldest IBI value 
          runningTotal += rate[i];          // add up the 9 oldest IBI values
        }
        
    rate[9] = IBI;                          // add the latest IBI to the rate array
    runningTotal += rate[9];                // add the latest IBI to runningTotal
    runningTotal /= 10;                     // average the last 10 IBI values 
    BPM = 60000/runningTotal;               // how many beats can fit into a minute? that's BPM!
    lcd.clear();
    lcd.print("Heart Beat Rate:");
    lcd.setCursor(0,1);
    lcd.print(BPM);
    lcd.print(" ");
    lcd.write(1);
    QS = true;                              // set Quantified Self flag 
    // QS FLAG IS NOT CLEARED INSIDE THIS ISR
    }                       
}

  if (Signal < thresh && Pulse == true){     // when the values are going down, the beat is over
      digitalWrite(blinkPin,LOW);            // turn off pin 13 LED
      Pulse = false;                         // reset the Pulse flag so we can do it again
      amp = P - T;                           // get amplitude of the pulse wave
      thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
      P = thresh;                            // reset these for next time
      T = thresh;
     }
  
  if (N > 2500){                             // if 2.5 seconds go by without a beat
      thresh = 512;                          // set thresh default
      P = 512;                               // set P default
      T = 512;                               // set T default
      lastBeatTime = sampleCounter;          // bring the lastBeatTime up to date        
      firstBeat = true;                      // set these to avoid noise
      secondBeat = true;                     // when we get the heartbeat back
     }
  
  sei();                                     // enable interrupts when youre done!
}

Schematics

Circuit Diagram
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