Heart Rate Pulse Sensor – BPM Meter using OLED & ESP32

Introduction

Pulse sensors are used in several projects for athletes, gaming, home appliances, and mobile phone developers where there is a need for reading heart rate data. In this tutorial, I’ll focus on one of the low-power plug-and-play pulse sensors for Arduino.

What is a Pulse Sensor?

A pulse sensor is a device used to detect a change in the volume of a blood vessel that occurs when the heart pumps blood. This volume change is called a pulse wave and is the basis of determining heart rate.

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5$ PCB Prototype

Hardware Components

You will require the following hardware for the Heart Rate Monitor.

S.no	Component	Value	Qty
1.	Arduino UNO	–	1
2.	USB Cable Type A to B	–	1
3.	DC Power for Arduino	–	1
4.	Pulse Sensor	–	1
5.	Jumper Wires	–	1

Pulse Sensor Overview

The Pulse Sensor Amped is a plug-and-play heart-rate sensor for Arduino. It can be used by students, artists, athletes, makers, and game & mobile developers who want to easily incorporate live heart-rate data into their projects.It essentially combines a simple optical heart rate sensor with amplification and noise cancellation circuitry making it fast and easy to get reliable pulse readings. Also, it sips power with just 4mA current draw at 5V so it’s great for mobile applications.

Pulse Sensor Pinout

Pulse Sensor with Arduino

I’ll now show you a simple practical application of this sensor where you can display the pulse waveform and the corresponding heart rate in beats per minute (BMP) reading on an SSD1306 OLED.

Before proceeding you should know how to use the SSD1306 OLED with Arduino and in case you need assistance on this issue you can visit my other tutorial where I have written in-depth about the SSD1306 OLED and its use with Arduino:

• Interfacing SSD1306 OLED with Arduino.

The setup is as shown in the schematic below. The SSD1306 OLED uses I2C communication and therefore we simply connect the SDA and SCL to A4 and A5 for Arduino UNO

Schematic

Make connections according to the circuit diagram given below.

Wiring / Connections

Arduino	Pulse Sensor	OLED
5V	VCC	VCC
GND	GND	GND
A0	SIG
A4		SCL
A5		SDA

Installing Arduino IDE

First, you need to install Arduino IDE Software from its official website Arduino. Here is a simple step-by-step guide on “How to install Arduino IDE“.

Installing Libraries

Before you start uploading a code, download and unzip the following libraries at /Progam Files(x86)/Arduino/Libraries (default), in order to use the sensor with the Arduino board. Here is a simple step-by-step guide on “How to Add Libraries in Arduino IDE“.

• SSD1306

Code

Now copy the following code and upload it to Arduino IDE Software.

#include <Adafruit_SSD1306.h>
 
#define OLED_Address 0x3C        
Adafruit_SSD1306 oled(128, 64);  

int x=0;
int lastx=0;
int lasty=0;
int LastTime=0;
int ThisTime;
bool BPMTiming=false;
bool BeatComplete=false;
int BPM=0;
#define UpperThreshold 518
#define LowerThreshold 509

void setup() {
  oled.begin(SSD1306_SWITCHCAPVCC, OLED_Address);
  oled.clearDisplay();
  oled.setTextSize(2);
}


void loop() 
{
  if(x>127)  
  {
    oled.clearDisplay();
    x=0;
    lastx=x;
  }

  ThisTime=millis();
  int value=analogRead(0);
  oled.setTextColor(WHITE);
  int y=60-(value/16);
  oled.writeLine(lastx,lasty,x,y,WHITE);
  lasty=y;
  lastx=x;
  // calc bpm

  if(value>UpperThreshold)
  {
    if(BeatComplete)
    {
      BPM=ThisTime-LastTime;
      BPM=int(60/(float(BPM)/1000));
      BPMTiming=false;
      BeatComplete=false;
      tone(8,1000,250);
    }
    if(BPMTiming==false)
    {
      LastTime=millis();
      BPMTiming=true;
    }
  }
  if((value<LowerThreshold)&(BPMTiming))
    BeatComplete=true;
    
    // display bpm
  oled.writeFillRect(0,50,128,16,BLACK);
  oled.setCursor(0,50);
  oled.print(BPM);
  oled.print(" BPM");
  oled.display();
  x++;
}

Applications

• Athletes
• Gaming
• Home appliances
• Mobile phone developers etc

Conclusion.

We hope you have found this Heart Rate Monitor Circuit very useful. If you feel any difficulty in making it feel free to ask anything in the comment section.