Grove - Ear-clip Heart Rate Sensor

The Heart Rate Ear clip kit contains a ear clip and a receiver module. The heart rate measure kit can be used to monitor heart rate of patient and athlete. The result can be displayed on a screen via the serial port and can be saved for analysis. The entire system is a high sensitivity, low power consumption and portable.
Model: MED03212P

Features

Low power consumption
Convenient to use
High sensitivity
Fully RoHS compliant

Specification

Item	Min	Typical	Max	Unit
Voltage	3.0	5.0	5.25	V
Work Current	6.5			mA
Length of ear clip wire	120			cm
Measures Range	≥30/min			-

Application Ideas

Heart rate monitor.

Usage

The following sketch demonstrates a simple application of using the Ear-clip Heart Rate Sensor to measure heart rate.

Connect this module to the digital port D2 on Grove-Base shield. And connect Grove-LED to Digital port 4.
Plug the Base Shield into Arduino/Seeeduino.

Copy and paste code below to a new Arduino sketch.

// Function: This program can be used to measure heart rate, the lowest pulse in the program be set to 30.
//         Use an external interrupt to measure it.
// Hardware: Grove - Ear-clip Heart Rate Sensor, Grove - Base Shield, Grove - LED
// Arduino IDE: Arduino-1.0
// Author: FrankieChu		
// Date: Jan 22, 2013
// Version: v1.0
// by www.seeedstudio.com
#define LED 4//indicator, Grove - LED is connected with D4 of Arduino
boolean led_state = LOW;//state of LED, each time an external interrupt 
								//will change the state of LED
unsigned char counter;
unsigned long temp[21];
unsigned long sub;
bool data_effect=true;
unsigned int heart_rate;//the measurement result of heart rate

const int max_heartpluse_duty = 2000;//you can change it follow your system's request.
						//2000 meams 2 seconds. System return error 
						//if the duty overtrip 2 second.
void setup()
{
	pinMode(LED, OUTPUT);
	Serial.begin(9600);
	Serial.println("Please ready your chest belt.");
	delay(5000);
	arrayInit();
	Serial.println("Heart rate test begin.");
	attachInterrupt(0, interrupt, RISING);//set interrupt 0,digital port 2
}
void loop()
{
	digitalWrite(LED, led_state);//Update the state of the indicator
}
/*Function: calculate the heart rate*/
void sum()
{
 if(data_effect)
    {
      heart_rate=1200000/(temp[20]-temp[0]);//60*20*1000/20_total_time 
      Serial.print("Heart_rate_is:\t");
      Serial.println(heart_rate);
    }
   data_effect=1;//sign bit
}
/*Function: Interrupt service routine.Get the sigal from the external interrupt*/
void interrupt()
{
    temp[counter]=millis();
	Serial.println(counter,DEC);
    Serial.println(temp[counter]);
    switch(counter)
	{
		case 0:
			sub=temp[counter]-temp[20];
			Serial.println(sub);
			break;
		default:
			sub=temp[counter]-temp[counter-1];
			Serial.println(sub);
			break;
	}
    if(sub>max_heartpluse_duty)//set 2 seconds as max heart pluse duty
	{
		data_effect=0;//sign bit
		counter=0;
		Serial.println("Heart rate measure error,test will restart!" );
		arrayInit();
	}
    if (counter==20&&data_effect)
    {
		counter=0;
		sum();
    }
    else if(counter!=20&&data_effect)
    counter++;
    else 
    {
		counter=0;
		data_effect=1;
    }
    
}
/*Function: Initialization for the array(temp)*/
void arrayInit()
{
	for(unsigned char i=0;i < 20;i ++)
	{
		temp[i]=0;
	}
	temp[20]=millis();
}

Upload the code, please click here if you do not know how to upload.
Make sure the sensor contacts your ear skin. This is the signal when we are measuring the heart rate:

In the left of the figures which is a waveform diagram of the detected heartbeat, A high pulse comes when beating. Note: If the serial monitor return an error message, please change the position of the sensor.

Resources

Grove - Ear-clip Heart Rate Sensor Demo code

Support

If you have questions or other better design ideas, you can go to our forum or wish to discuss.