still alive? heartbeat (IR)sensor report

Principles: Sense heart rate by using a pair of infrared emitter and reciever, next to each other on top the measuring site on top of the finger. The light bounces from the emitter to the detector across the site. with each heart beat the heart contracts and there is a surge of arterial blood, which momentarily increases arterial blood volume across the measuring site. This results in more light absorption during the surge. if light signals received at the photodetector are looked at 'as a waveform', there should be peaks with each heartbeat and troughs between heartbeats.
(http://www.oximetry.org/pulseox/principles.htm)



Sensors: Infrared Emitters and Detectors
SKU#: SEN-00241
Price: $1.95

Description: Side-looking Infrared Emitters and IR Detectors. These simple devices operate at 940nm and work well for generic IR systems including remote control and touch-less object sensing. Using a simple ADC on any microcontroller will allow variable readings to be collected from the detector. The emitter is driven up to 50mA with a current limiting resistor as with any LED device. The detect is a NPN transistor that is biased by incoming IR light.

datasheet:

IR Emitter (Clear)

IR Detector (Tinted pink)

how it works:

R1	270 ohm resistor
R2	10k resistor
LED1	Infrared LED
Q1	Infrared-sensitive photoresistor

Circuit: (simple one without amplifier)

Dubug process: The signal is sometimes weak, sometimes strong. It may be because of my finger position, my IR sensors which are very fragile or my circuit, or just simply because the signal is weak.

pot is used to set the threshold. So I could detect the heartbeat.

Code:

arduino:

/* I AM ALIVE heart beat led
* by meng li based on the code by Jeff Gray - 2008
* ----------------
* Triggers a one time event when value goes over threshold,
* and a different trigger once the value goes back below the threshold
*/

int an1,an2 = 0;
int redLedPin =13;
boolean triggered = false;

void setup(){
Serial.begin(9600);
pinMode(redLedPin, OUTPUT); // set the red LED pin to be an output
// Serial.println("Starting");
}
void loop(){
// read analog value in
int an2 = analogRead(0);
Serial.print("Y");
Serial.println(an2,DEC);
//threshold
int an1= analogRead(5);
Serial.print("X");
Serial.println(an1,DEC);


if(an1 > an2 && !triggered){
triggered = true;
digitalWrite(redLedPin, HIGH); // turn off the red LED
}
if(an1 <= an2 && triggered){
triggered = false;
digitalWrite(redLedPin, LOW); // turn off the red LED
}
}

processing:

import processing.serial.*;

String buff = "";
int val = 0;
int NEWLINE = 10;
int xPos,yPos,zPos = 0;
int displaySize = 2;
int an1, an2, an3;
//an1 pot; an2 ir;

Serial port;

void setup(){
background(80);
size(800,600);
smooth();

port = new Serial(this, Serial.list()[1], 9600);
}

void draw(){
// new background over old
fill(80,5);
noStroke();
rect(0,0,width,height);

// wipe out a small area in front of the new data
fill(80);
rect(xPos+displaySize,0,50,height);

// check for serial, and process
while (port.available() > 0) {
serialEvent(port.read());
}

}


void serialEvent(int serial) {
print("A"); //header variable, so we know which sensor value is which
println(an1); //send as a ascii encoded number - we'll turn it back into a number at the other end
//Serial.print(10, BYTE); //terminating character

print("B"); //header variable, so we know which sensor value is which
println(an2); //send as a ascii encoded number - we'll turn it back into a number at the other end
//Serial.print(10, BYTE); //terminating character


if(serial != '\n') {
buff += char(serial);
}
else {
int curX = buff.indexOf("X");
int curY = buff.indexOf("Y");


if(curX >=0){
String val = buff.substring(curX+1);
an1 = Integer.parseInt(val.trim());

xPos++;
if(xPos > width) xPos = 0;

sensorTic1(xPos,an1);
}
if(curY >=0){
String val = buff.substring(curY+1);
an2 = Integer.parseInt(val.trim());

yPos++;
if(yPos > width) yPos = 0;

sensorTic2(yPos,an2);
}

// Clear the value of "buff"
buff = "";
}
}

void sensorTic1(int x, int y){
stroke(0,0,255);
fill(0,0,255);
ellipse(x,y,displaySize,displaySize);
}

void sensorTic2(int x, int y){
stroke(255,0,0);
fill(255,0,0);
ellipse(x,y,displaySize,displaySize);
}




Since the signals to different people are different. Some seems have very weak heartbeat or even no signal according to my way of sensing. So I decided to use amplifier to filter and amplify signals.

(thanks to justin downs and yanyan cao at itp)

http://johnhenryshammer.com/TEChREF/opAmps/IRHEARTSCHMATIC.html

Code:

arduino:
// from justin)

#define mask 255 // kill top bits

int potPin = 0; // select the input pin for the pot

int ledPin = 13; // select the pin for the LED

int val = 16706; // variable to store the value coming from the sensor

int val2 =0;

int a =0;

int b =0;

int beats[]= {0,0,0,0,0};// to track last five reads for a pattern

boolean beated = false;

//function dec

boolean getBioData();


void setup() {
pinMode(ledPin, OUTPUT); // declare the ledPin as an OUTPUT
Serial.begin(9600);
}

void loop() {
char check=' ';
val = analogRead(potPin); // read the value from the sensor
if (Serial.read() =='a'){ // check buffer for an 'a'
val2 = val;
b= val & mask;
a =((val2>>8) & mask); //just in case mask
delay(20);
// Serial.print("b"); // debug
// Serial.print(b);
Serial.print(a,BYTE);
Serial.print(b,BYTE);
if (getBioData()){ // call bio function
Serial.print('b',BYTE);
}
else Serial.print('n',BYTE);
}
}
boolean getBioData(){
int beatVal = analogRead(potPin); // read the value from the sensor
beats[4] = beatVal; // put in back of array
int beatDif = beats[5 - 1] - beats[0];
for (int i = 0; i < 5;i++){
beats[i] = beats[i+1]; // push zero out front
}
// check for beat
if ( beatDif > 10 && (beated != true)){
beated = true;
return true;
}
else if( beatDif < 2 ){
beated = false;
return false;
}
else return false;
}


processing:

//CODE USED TO GET DATA AND GRAPH IT FROM THE

// HEART MONITOR ARDUINO CODE

// in Java




import processing.serial.*;


Serial port; // Create object from Serial class

int val; // Data received from the serial port

int WIDTH=800; // set width

int number=0;

int num[] = new int[3];

int points[]= new int[WIDTH]; // points to be drawn from incoming data

char beat=' ';

int beats=0;

int dropNum[] = new int[4]; // array used to compare data not needed

void setup()
{
println(Serial.list());
size(WIDTH, 700);
frameRate(30);
// Open the port that the board is connected to and use the same speed (9600 bps)
port = new Serial(this,Serial.list()[1], 9600);
}

void draw()
{
background(0);// to erase
port.write('a');
if (2 < port.available()) { // wait for three bytes
for (int i=0;i<3;i++){
num[i] = port.read(); // read them into an array
}
//println( num[0]);
//println( num[1]);
number = (num[0] << 8)+num[1]; // num range add two incoming bytes together after shifting
beat = (char) num[2]; // look to see if there is a 'b' to signal a beat
println(beats);
}
stroke(0,255,100); // color stroke
if (beat == 'b'){// sent from arduino
beats++;
}
// draw heart beat data
strokeWeight(1);
points[(WIDTH/2)] = number; // strat drawing half way accross screen give current reading to array
//goes through all points and draws a line between consecutive ones
for (int i=1 ;i points[i]= points[i+1];
line(i,height-points[i-1]-40,i,height-points[i]-40);
}
}




Documentation:
without amplifier:


with amplifier: