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.

Features

• Low power consumption

• Convenient to use

• High sensitivity

• Fully RoHS compliant

!!!Tip More details about Grove modules please refer to Grove System

Specifications

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.

Platforms Supported

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.

• Make sure the sensor contacts your ear skin. This is the signal when we are measuring the heart rate:

In the first 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