My workbench

noreply@blogger.com (Francis Poisson-Gagnon) — Sun, 31 Jan 2010 20:09:00 +0000

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

noreply@blogger.com (Francis Poisson-Gagnon) — Wed, 01 Apr 2009 19:03:00 +0000

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

22 Wire Electronics

My workbench

Heart Rate Monitor