I am trying to read the Beats per minute through my Arduino based set up and a MAX30102 pulse sensor (datasheet).
The strength of the pulse is much weaker than usual.
Below is the visualization with signal and noise, which shows difference between rat pulse and human pulse.
Actual:
Theoretical:
The above visualizations are achieved through the below code.
/*
MAX30102- Heart Rate Pulse Detection-Module
Home
Based on Arduino Library Example
*/
#include <Wire.h>
#include "MAX30105.h"
MAX30105 particleSensor;
void setup()
{
Serial.begin(19200);
Serial.println("Initializing...");
// Initialize sensor
if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
{
Serial.println("MAX30105 was not found. Please check wiring/power. ");
while (1);
}
//Setup to sense a nice looking saw tooth on the plotter
byte ledBrightness = 0x1F; //Options: 0=Off to 255=50mA
byte sampleAverage = 8; //Options: 1, 2, 4, 8, 16, 32
byte ledMode = 3; //Options: 1 = Red only, 2 = Red + IR, 3 = Red + IR + Green
int sampleRate = 100; //Options: 50, 100, 200, 400, 800, 1000, 1600, 3200
int pulseWidth = 411; //Options: 69, 118, 215, 411
int adcRange = 4096; //Options: 2048, 4096, 8192, 16384
particleSensor.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth,
adcRange); //Configure sensor with these settings
//Arduino plotter auto-scales annoyingly. To get around this, pre-populate
//the plotter with 500 of an average reading from the sensor
//Take an average of IR readings at power up
const byte avgAmount = 64;
long baseValue = 0;
for (byte x = 0 ; x < avgAmount ; x++)
{
baseValue += particleSensor.getIR(); //Read the IR value
}
baseValue /= avgAmount;
//Pre-populate the plotter so that the Y scale is close to IR values
for (int x = 0 ; x < 500 ; x++)
Serial.println(baseValue);
}
void loop()
{
Serial.println(particleSensor.getIR()); //Send raw data to plotter
}
And below is a measure of the BPM measurements of rat and human compared.
Rat BPM:
Human BPM:
Below is the code used to achieve the above.
/*
Optical Heart Rate Detection (PBA Algorithm) using the MAX30105 Breakout
By: Nathan Seidle @ SparkFun Electronics
Date: October 2nd, 2016
https://github.com/sparkfun/MAX30105_Breakout
This is a demo to show the reading of heart rate or beats per minute (BPM) using
a Penpheral Beat Amplitude (PBA) algorithm.
It is best to attach the sensor to your finger using a rubber band or other tightening
device. Humans are generally bad at applying constant pressure to a thing. When you
press your finger against the sensor it varies enough to cause the blood in your
finger to flow differently which causes the sensor readings to go wonky.
Hardware Connections (Breakoutboard to Arduino):
-5V = 5V (3.3V is allowed)
-GND = GND
-SDA = A4 (or SDA)
-SCL = A5 (or SCL)
-INT = Not connected
The MAX30105 Breakout can handle 5V or 3.3V I2C logic. We recommend powering the board
with 5V
but it will also run at 3.3V.
*/
#include <Wire.h>
#include "MAX30105.h"
#include "heartRate.h"
MAX30105 particleSensor;
const byte RATE_SIZE = 4; //Increase this for more averaging. 4 is good.
byte rates[RATE_SIZE]; //Array of heart rates
byte rateSpot = 0;
long lastBeat = 0; //Time at which the last beat occurred
float beatsPerMinute;
int beatAvg;
void setup()
{
Serial.begin(115200);
Serial.println("Initializing...");
// Initialize sensor
if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
{
Serial.println("MAX30105 was not found. Please check wiring/power. ");
while (1);
}
Serial.println("Place your index finger on the sensor with steady pressure.");
particleSensor.setup(); //Configure sensor with default settings
particleSensor.setPulseAmplitudeRed(0x0A); //Turn Red LED to low to indicate sensor is
running
particleSensor.setPulseAmplitudeGreen(0); //Turn off Green LED
}
void loop()
{
long irValue = particleSensor.getIR();
if (checkForBeat(irValue) == true)
{
//We sensed a beat!
long delta = millis() - lastBeat;
lastBeat = millis();
beatsPerMinute = 60 / (delta / 1000.0);
if (beatsPerMinute < 255 && beatsPerMinute > 20)
{
rates[rateSpot++] = (byte)beatsPerMinute; //Store this reading in the array
rateSpot %= RATE_SIZE; //Wrap variable
//Take average of readings
beatAvg = 0;
for (byte x = 0 ; x < RATE_SIZE ; x++)
beatAvg += rates[x];
beatAvg /= RATE_SIZE;
}
}
Serial.print("IR=");
Serial.print(irValue);
Serial.print(", BPM=");
Serial.print(beatsPerMinute);
Serial.print(", Avg BPM=");
Serial.print(beatAvg);
if (irValue < 50000)
Serial.print(" No finger?");
Serial.println();
}
Obviously the measurement of the real BPM is faulted as a healthy subject could never have a BPM like that.
I would like to know how to modify the above code to measure the BPM and to eliminate the noise (In order of priority).
