In this article, we will discuss pulse sensor and Arduino Uno and build a full responsive Heart Rate Monitor using character LCD, Amped Pulse Sensor Amped and Arduino Compatible Plug and Play Heart Rate Sensors.
It can be used by students, artists, athletes, manufacturers, games and mobile developers who can easily incorporate live heart rate data into their projects.
The pulse sensor adds amplification and noise cancellation circuitry to the hardware. Obviously faster and easier to obtain reliable pulse readings. Pulse Sensor Amps can use 3V or 5V Arduino.
I am going to share a project that is very handy people can make at home. You can monitor your heart rate at home and I want to share it on the guide and on youtube so that people can have a cheap DIY reliable heart rate monitor. Go to the next step in schematics, codes, and parts lists.
Specification of project
Diameter = 0.625″ (~16mm)
Overall thickness = 0.125″ (~3mm)
Working Voltage = 3V to 5V
Working Current = ~4mA at 5V
Collect the Hardware
For this project, you just need few things such as
- Arduino Uno Board.
- Pulse Sensor Arduino
- Jumper Wires
- LCD
- Potentiometer 10K
- 2 LEDs
- Breadboard
Wired Up Everything
Connect the wired as mention below
Connect Pulse Sensor to Arduino Uno Board as following:
- to +5V
- to GND
S tO A0
Connect LCD to Arduino Uno Board as following:
VSS to GND
VDD to +5
RS to 12
RW to GND
E to D11
D4 to D5
D5 to D4
D6 to D3
D7 to D2
A/VSS to +5V
K/VDD to GND
Connect 10K Potentiometer to LCD as following (refer image for potentiometer pinout) :
GND to GND
Data to v0
VCC to +5V
Connect LED to Arduino as follows:
LED1 (RED, blinkPin) to D13
LED2 (GREEN, fadeRate) to D8
Final Connection
So final connection will look like this
Upload the Source Code
After the wired up everything connects it up to your computer upload the source code Arduino so if you are very new to Arduino programming then I will suggest you to read my previous article for beginner, here Beginner guide for Arduino
Add the zip library from here Github
Upload code via Arduino ide
////////////////Technical Ustaad /////////////////////////
#include <LiquidCrystal.h>
// Variables
int pulsePin = 0; // Pulse Sensor purple wire connected to analog pin 0
int blinkPin = 13; // pin to blink led at each beat
int fadePin = 8; // pin to do fancy classy fading blink at each beat
int fadeRate = 0; // used to fade LED on with PWM on fadePin
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// Volatile Variables, used in the interrupt service routine!
volatile int BPM; // int that holds raw Analog in 0. updated every 2mS
volatile int Signal; // holds the incoming raw data
volatile int IBI = 600; // int that holds the time interval between beats! Must be seeded!
volatile boolean Pulse = false; // “True” when User’s live heartbeat is detected. “False” when not a “live beat”.
volatile boolean QS = false; // becomes true when Arduoino finds a beat.
// Regards Serial OutPut — Set This Up to your needs
static boolean serialVisual = true; // Set to ‘false’ by Default. Re-set to ‘true’ to see Arduino Serial Monitor ASCII Visual Pulse
volatile int rate[10]; // array to hold last ten IBI values
volatile unsigned long sampleCounter = 0; // used to determine pulse timing
volatile unsigned long lastBeatTime = 0; // used to find IBI
volatile int P = 512; // used to find peak in pulse wave, seeded
volatile int T = 512; // used to find trough in pulse wave, seeded
volatile int thresh = 525; // used to find instant moment of heart beat, seeded
volatile int amp = 100; // used to hold amplitude of pulse waveform, seeded
volatile boolean firstBeat = true; // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = false; // used to seed rate array so we startup with reasonable BPM
void setup()
{
pinMode(blinkPin,OUTPUT); // pin that will blink to your heartbeat!
pinMode(fadePin,OUTPUT); // pin that will fade to your heartbeat!
Serial.begin(115200); // we agree to talk fast!
interruptSetup(); // sets up to read Pulse Sensor signal every 2mS
// IF YOU ARE POWERING The Pulse Sensor AT VOLTAGE LESS THAN THE BOARD VOLTAGE,
// UN-COMMENT THE NEXT LINE AND APPLY THAT VOLTAGE TO THE A-REF PIN
// analogReference(EXTERNAL);
}
// Where the Magic Happens
void loop()
{
serialOutput();
if (QS == true) // A Heartbeat Was Found
{
// BPM and IBI have been Determined
// Quantified Self “QS” true when arduino finds a heartbeat
fadeRate = 255; // Makes the LED Fade Effect Happen, Set ‘fadeRate’ Variable to 255 to fade LED with pulse
serialOutputWhenBeatHappens(); // A Beat Happened, Output that to serial.
QS = false; // reset the Quantified Self flag for next time
}
ledFadeToBeat(); // Makes the LED Fade Effect Happen
delay(20); // take a break
}
void ledFadeToBeat()
{
fadeRate -= 15; // set LED fade value
fadeRate = constrain(fadeRate,0,255); // keep LED fade value from going into negative numbers!
analogWrite(fadePin,fadeRate); // fade LED
}
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
}
void serialOutput()
{ // Decide How To Output Serial.
if (serialVisual == true)
{
arduinoSerialMonitorVisual(‘-‘, Signal); // goes to function that makes Serial Monitor Visualizer
}
else
{
sendDataToSerial(‘S’, Signal); // goes to sendDataToSerial function
}
}
void serialOutputWhenBeatHappens()
{
if (serialVisual == true) // Code to Make the Serial Monitor Visualizer Work
{
Serial.print(“*** Heart-Beat Happened *** “); //ASCII Art Madness
Serial.print(“BPM: “);
Serial.println(BPM);
lcd.clear();
lcd.print(“BPM: “);
lcd.print(BPM);
}
else
{
sendDataToSerial(‘B’,BPM); // send heart rate with a ‘B’ prefix
sendDataToSerial(‘Q’,IBI); // send time between beats with a ‘Q’ prefix
}
}
void arduinoSerialMonitorVisual(char symbol, int data )
{
const int sensorMin = 0; // sensor minimum, discovered through experiment
const int sensorMax = 1024; // sensor maximum, discovered through experiment
int sensorReading = data; // map the sensor range to a range of 12 options:
int range = map(sensorReading, sensorMin, sensorMax, 0, 11);
// do something different depending on the
// range value:
switch (range)
{
case 0:
Serial.println(“”); /////ASCII Art Madness
break;
case 1:
Serial.println(“—“);
break;
case 2:
Serial.println(“——“);
break;
case 3:
Serial.println(“———“);
break;
case 4:
Serial.println(“————“);
break;
case 5:
Serial.println(“————–|-“);
break;
case 6:
Serial.println(“————–|—“);
break;
case 7:
Serial.println(“————–|——-“);
break;
case 8:
Serial.println(“————–|———-“);
break;
case 9:
Serial.println(“————–|—————-“);
break;
case 10:
Serial.println(“————–|——————-“);
break;
case 11:
Serial.println(“————–|———————–“);
break;
}
}
void sendDataToSerial(char symbol, int data )
{
Serial.print(symbol);
Serial.println(data);
}
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
// NOW IT’S TIME TO LOOK FOR THE HEART BEAT
// 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(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;
}
}
if(firstBeat) // if it’s the first time we found a beat, if firstBeat == TRUE
{
firstBeat = false; // clear firstBeat flag
secondBeat = true; // set the second beat flag
sei(); // enable interrupts again
return; // IBI value is unreliable so discard it
}
// 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!
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 = false; // when we get the heartbeat back
}
sei(); // enable interrupts when youre done!
}// end isr
/////////////////////////////////////////////////////////
DONE!
Now just open the terminal of Arduino UNO by pressing “Ctrl”+ “Shift” + “M” keys simultaneously in 115200 port as shown in figure
NOTE : DO NOT connect the Pulse Sensor to your body while your computer or arduino is being powered from the mains AC line. That goes for charging laptops and DC power supplies.
Here is the test video for this project
