My workbench

Here is a picture of my workbench. No project going on here. It all happens at Cegep where I am currently working on my final project. A energy monitoring dashboard based on TI MSP430. I'll talk about it here soon.

Heart Rate Monitor

The first Arduino's project I am working on: A heart rate monitor. I am using this project to exercices with the Arduino platform and experimenting things with Polar technologies. 

 

I have received the Polar Heart Rate Module from Sparkfun yesterday  (http://www.sparkfun.com/commerce/product_info.php?products_id=8660) to replace the Rick Moll's circuit (http://rick.mollprojects.com/hrm/index.html) which is pretty hard to use due to its sensitivity to ambient electromagnetic field(TV, 120V AC cable...) and has a poor range (~30cm). Th module is now more easy to use, the datasheet is pretty clear about the pinout and the connection to a µController. To be able to use coded and non-coded transmitter you only hook-up the HR pin to the interruption output of the Arduino (Digital 2 or 3) which outpout a 1 ms pulse when a pulse is detected without the "coded pulse" as the FPLS pin would do.

Here is my schematic like it was with the Rick Moll's circuit:

Here is my Arduino code which looks to work pretty well with the module:

#define NUMREADINGS 4

#define DEADTIME 2000

int  D3 = 3, D4 = 4, D5 =5, D6 = 6, D7 = 7, D8 = 8;

volatile int onetime;

volatile unsigned long beats = 0, lastTime, period;

int readings[NUMREADINGS];                // the readings from the analog input

int index = 0;                            // the index of the current reading

int total = 0;                            // the running total

int average = 0;                          // the average

void setup()

{

  pinMode(D3, OUTPUT);     //P3 to P8 as output

  pinMode(D4, OUTPUT);

  pinMode(D5, OUTPUT);

  pinMode(D6, OUTPUT);

  pinMode(D7, OUTPUT);

  pinMode(D8, OUTPUT);

  attachInterrupt(0, pulse, RISING);   //call pulse function when an interrupt is detected on Port 2;

  for (int i = 0; i <>

    readings[i] = 0;                      // initialize all the readings to 0

  }

}

void loop()

{

int frequence; 

  

if ((beats > 1) && (onetime != 1)) {                //make sur it passes only one time when a pulse is detected

  frequence = (60000 / period);                    //calculate bpm using time between the two pulses

  if ((frequence >= 40) && (frequence <= 220))  {   //if bpm is between 40 and 220

    total -= readings[index];                       // subtract the last reading

    readings[index] = frequence;

    total += readings[index];                       // add the reading to the total

    index = (index + 1);                            // advance to the next index

    if (index >= NUMREADINGS) {                     // if we're at the end of the array...

      index = 0;                                    // ...wrap around to the beginning

      average = total / NUMREADINGS;                // calculate the average

    }

  }

  onetime = 1;                                      //Puts the one time flag to 1

}

if ((millis() - lastTime) > DEADTIME) {

  average = 0;

  index = 0;

}

ssegment(average);

}

void pulse()

{

  if (beats > 0){

    period =  millis() - lastTime;

  }

  lastTime = millis();

  beats++;

  onetime = 0;                                     //Puts the one time flag to 0 

}

void ssegment(int fc) {  

  int unite, dizaine, centaine;

  unite = (fc % 10);                  //put the first number of the decimal value of bpm in unite variable

  dizaine = (((fc % 100) - unite)/10);//put the second number of the decimal value of bpm in dizaine variable 

  centaine = (((fc % 1000) - dizaine - unite)/100);//put the third number of the decimal value of bpm in centaine variable

  

  

  digitalWrite(D7, LOW);  //address of first number

  digitalWrite(D8, HIGH);

  chiffre(unite);         //send unite to funtion chiffre to be displayed

  delay(1);

  digitalWrite(D7, HIGH);//address of second number

  digitalWrite(D8, LOW);

  chiffre(dizaine);      //send dizaine to funtion chiffre to be displayed

  delay(1);

  digitalWrite(D7, HIGH);//address of third number

  digitalWrite(D8, HIGH);

  chiffre(centaine);     //send centaine to funtion chiffre to be displayed

  delay(1);

  

}

void chiffre(int i) {  //send bcd value of decimal number to ports D3 to D6

  switch(i){

    case 1:

      digitalWrite(D6, HIGH);

      digitalWrite(D3, LOW);

      digitalWrite(D4, LOW);

      digitalWrite(D5, LOW);

      break;

    case 2:

      digitalWrite(D6, LOW);

      digitalWrite(D3, HIGH);

      digitalWrite(D4, LOW);

      digitalWrite(D5, LOW);

      break;

    case 3:

      digitalWrite(D6, HIGH);

      digitalWrite(D3, HIGH);

      digitalWrite(D4, LOW);

      digitalWrite(D5, LOW);

      break;

    case 4:

      digitalWrite(D6, LOW);

      digitalWrite(D3, LOW);

      digitalWrite(D4, HIGH);

      digitalWrite(D5, LOW);

      break;

    case 5:

      digitalWrite(D6, HIGH);

      digitalWrite(D3, LOW);

      digitalWrite(D4, HIGH);

      digitalWrite(D5, LOW);

      break;

    case 6:

      digitalWrite(D6, LOW);

      digitalWrite(D3, HIGH);

      digitalWrite(D4, HIGH);

      digitalWrite(D5, LOW);

      break;

    case 7:

      digitalWrite(D6, HIGH);

      digitalWrite(D3, HIGH);

      digitalWrite(D4, HIGH);

      digitalWrite(D5, LOW);

      break;

    case 8:

      digitalWrite(D6, LOW);

      digitalWrite(D3, LOW);

      digitalWrite(D4, LOW);

      digitalWrite(D5, HIGH);

      break;

    case 9:

      digitalWrite(D6, HIGH);

      digitalWrite(D3, LOW);

      digitalWrite(D4, LOW);

      digitalWrite(D5, HIGH);

      break;

    case 0:

      digitalWrite(D6, LOW);

      digitalWrite(D3, LOW);

      digitalWrite(D4, LOW);

      digitalWrite(D5, LOW);

      break;

   }

}

If you have any question, I will be happy to help you.

Additional Ressources:

- Polar Heart Rate Module RMCM01 on Sparkfun

- Polar Heart Rate Module RMCM01 datasheet

- Information about Arduino

- Rick Moll's project