next topic »

[on:]

Hi,

im wondering how i can make a simple funktion that reads the analoge value from a pulse sensor (i bought a premade sensor already), then writes high to a digital port. So lets say that the pulse is moving between 100 & 120, id like the avr to understand that this is the normal pulse, when the pulse leaves the pattern — either becoming higher or lowe id like the avr to detect the change in the patterns and write high (then low again) to a digital port. After writing low id like to detect the new pulse pattern and then detect when the pulse brakes the pattern.

Thank you
/S

[Reply #1 on:]

use them:

analogread
map
digitalwrite

[Reply #2 on:]

(i bought a premade sensor already)

But, you're not going to tell us which one. Well, then, how are we supposed to write your code to read it?

either becoming higher or lowe id like the avr to detect the change in the patterns and write high (then low again) to a digital port.

Are you going to be able to see an LED that is turned on only for a new nanoseconds? Or is there supposed to be some interval between HIGH and LOW?

You want the same pin lit up for high and low pulse? 100 IS high, by the way. Typical resting pulse is more like 72.

[Reply #3 on:]

What sort of speeds are you talking about.  If it's a commercial sensor can you provide a pointer to the model and/or specs?

Also, moving between 100 and 120 "whats"?  Volts, nano-seconds, feet above mean sea level?

John

[Reply #4 on:]

Sorry, quite new to this.

i bought this
http://pulsesensor.com/
The idea is to start with a led then hook up a relay, basically i want to write high and low to a digital port (perhaps keep it as high for one second, before it becomes low again), lets say nr 13.

Ok, i just took 100 as an example. So id like the function to detect when the pulse leaves the resting interval.

I worked a bit with the code found here
http://pulsesensor.myshopify.com/pages/pulse-sensor-amped-arduino-v1dot1
but couldn't figure out how to spot the big changes in the pulse which would trigger pin nr 13.

/S

[Reply #5 on:]

but couldn't figure out how to spot the big changes in the pulse which would trigger pin nr 13.

Did you read the code walk through link? They do a pretty good job of describing the relationship between the code and the physical phenomenon being measured.

[Reply #6 on:]

Hi again, yes i did read the walk through link, the problem is that i don't under stand how to bring the code together — i also understand that it dose exactly what i want.
I got the sensor running but then it just blinks in the pase of the pulse..
/
S-P

[Reply #7 on:]

I got the sensor running but then it just blinks in the pase of the pulse..

So, you need to count the number of pulses in some period of time, and calculate beats per minute. Then, do something when beats per minute is above your threshold. Or below it.

[Reply #8 on:]

You can read analog pulses on digital pins by having the pulse charge a resistor-capacitor circuit and time how many loops until it drains from HIGH to LOW. That is the way that all cheap A/D converters (PC joystick port) work.

What size resistor and capacitor? Hehehe, I'm not the guy to ask as I don't know the best answer!

[Reply #9 on:]

I got the sensor running but then it just blinks in the pase of the pulse..

So, you need to count the number of pulses in some period of time, and calculate beats per minute. Then, do something when beats per minute is above your threshold. Or below it.

Isn't that what the sample code is doing, the code which is described on http://pulsesensor.myshopify.com/pages/pulse-sensor-amped-arduino-v1dot1? Which is the code ive been trying to compile.

Im running the code below to

Code:

//  VARIABLES
int pulsePin = 0;                 // Pulse Sensor purple wire connected to analog pin 0
int blinkPin = 13;                // pin to blink led at each beat
int fadePin = 5;                  // pin to do fancy classy fading blink at each beat
int fadeRate = 0;                 // used to fade LED on with PWM on fadePin


// these variables are volatile because they are used during the interrupt service routine!
volatile int BPM;                   // used to hold the pulse rate
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // holds the time between beats, the Inter-Beat Interval
volatile boolean Pulse = false;     // true when pulse wave is high, false when it's low
volatile boolean QS = false;        // becomes true when Arduoino finds a beat.


void setup(){
  pinMode(blinkPin,OUTPUT);         // pin that will blink to your heartbeat!
  pinMode(fadePin,OUTPUT);          // pin that will fade to your heartbeat!
  Serial.begin(115200);             // we agree to talk fast!
  interruptSetup();                 // sets up to read Pulse Sensor signal every 2mS
   // UN-COMMENT THE NEXT LINE IF YOU ARE POWERING The Pulse Sensor AT LOW VOLTAGE,
   // AND APPLY THAT VOLTAGE TO THE A-REF PIN
   //analogReference(EXTERNAL);   
}



void loop(){
  sendDataToProcessing('S', Signal);     // send Processing the raw Pulse Sensor data
  if (QS == true){                       // Quantified Self flag is true when arduino finds a heartbeat
        fadeRate = 255;                  // Set 'fadeRate' Variable to 255 to fade LED with pulse
        sendDataToProcessing('B',BPM);   // send heart rate with a 'B' prefix
        sendDataToProcessing('Q',IBI);   // send time between beats with a 'Q' prefix
        QS = false;                      // reset the Quantified Self flag for next time   
     }
 
  ledFadeToBeat();
 
  delay(20);                             //  take a break
}


void ledFadeToBeat(){
    fadeRate -= 15;                         //  set LED fade value
    fadeRate = constrain(fadeRate,0,255);   //  keep LED fade value from going into negative numbers!
    analogWrite(fadePin,fadeRate);          //  fade LED
  }


void sendDataToProcessing(char symbol, int data ){
    Serial.print(symbol);                // symbol prefix tells Processing what type of data is coming
    Serial.println(data);                // the data to send culminating in a carriage return
  }

[Reply #10 on:]

Im running the code below

No, you aren't. That code won't even compile. There are functions missing.

Defining a pin number, and then hoping that somehow, magically, data from that pin will be read and transformed into something useful is a waste of hoping. Save that for something more fun.

[Reply #11 on:]

I can recall many times when code would run and the results were interpreted completely wrong. To be honest, I've done it with every bug I've had any trouble with.

[Reply #12 on:]

Im running the code below

No, you aren't. That code won't even compile. There are functions missing.

Defining a pin number, and then hoping that somehow, magically, data from that pin will be read and transformed into something useful is a waste of hoping. Save that for something more fun.

Well — im not defining a pin then just hoping… I wish I was, since my problem would be more easily solved(!?) — by just stop hoping and actually start transforming data…

I guess you mean that the '  interruptSetup();' isn't found? It has to be included; which it is by creating a subfolder within the same folder as the other code is located. the namne of the new folder would be 'Interrupt' where a file called 'Interrupt.ino' is located and contains:

Code:

volatile int rate[10];                    // used to hold last ten IBI values
volatile unsigned long sampleCounter = 0;          // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;           // used to find the inter beat interval
volatile int P =512;                      // used to find peak in pulse wave
volatile int T = 512;                     // used to find trough in pulse wave
volatile int thresh = 512;                // used to find instant moment of heart beat
volatile int amp = 100;                   // used to hold amplitude of pulse waveform
volatile boolean firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = true;       // used to seed rate array so we startup with reasonable BPM


void interruptSetup(){     
  // Initializes Timer2 to throw an interrupt every 2mS.
  TCCR2A = 0x02;     // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
  TCCR2B = 0x06;     // DON'T FORCE COMPARE, 256 PRESCALER
  OCR2A = 0X7C;      // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
  TIMSK2 = 0x02;     // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
  sei();             // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED     
}


// THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE.
// Timer 2 makes sure that we take a reading every 2 miliseconds
ISR(TIMER2_COMPA_vect){                         // triggered when Timer2 counts to 124
    cli();                                      // disable interrupts while we do this
    Signal = analogRead(pulsePin);              // read the Pulse Sensor
    sampleCounter += 2;                         // keep track of the time in mS with this variable
    int N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

//  find the peak and trough of the pulse wave
    if(Signal < thresh && N > (IBI/5)*3){       // avoid dichrotic noise by waiting 3/5 of last IBI
        if (Signal < T){                        // T is the trough
            T = Signal;                         // keep track of lowest point in pulse wave
         }
       }
     
    if(Signal > thresh && Signal > P){          // thresh condition helps avoid noise
        P = Signal;                             // P is the peak
       }                                        // keep track of highest point in pulse wave
   
  //  NOW IT'S TIME TO LOOK FOR THE HEART BEAT
  // signal surges up in value every time there is a pulse
if (N > 250){                                   // avoid high frequency noise
  if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){       
    Pulse = true;                               // set the Pulse flag when we think there is a pulse
    digitalWrite(blinkPin,HIGH);                // turn on pin 13 LED
    IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
    lastBeatTime = sampleCounter;               // keep track of time for next pulse
         
         if(firstBeat){                         // if it's the first time we found a beat, if firstBeat == TRUE
             firstBeat = false;                 // clear firstBeat flag
             return;                            // IBI value is unreliable so discard it
            }   
         if(secondBeat){                        // if this is the second beat, if secondBeat == TRUE
            secondBeat = false;                 // clear secondBeat flag
               for(int i=0; i<=9; i++){         // seed the running total to get a realisitic BPM at startup
                    rate[i] = IBI;                     
                    }
            }
         
    // keep a running total of the last 10 IBI values
    word runningTotal = 0;                   // clear the runningTotal variable   

    for(int i=0; i<=8; i++){                // shift data in the rate array
          rate[i] = rate[i+1];              // and drop the oldest IBI value
          runningTotal += rate[i];          // add up the 9 oldest IBI values
        }
       
    rate[9] = IBI;                          // add the latest IBI to the rate array
    runningTotal += rate[9];                // add the latest IBI to runningTotal
    runningTotal /= 10;                     // average the last 10 IBI values
    BPM = 60000/runningTotal;               // how many beats can fit into a minute? that's BPM!
    QS = true;                              // set Quantified Self flag
    // QS FLAG IS NOT CLEARED INSIDE THIS ISR
    }                       
}

  if (Signal < thresh && Pulse == true){     // when the values are going down, the beat is over
      digitalWrite(blinkPin,LOW);            // turn off pin 13 LED
      Pulse = false;                         // reset the Pulse flag so we can do it again
      amp = P - T;                           // get amplitude of the pulse wave
      thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
      P = thresh;                            // reset these for next time
      T = thresh;
     }
 
  if (N > 2500){                             // if 2.5 seconds go by without a beat
      thresh = 512;                          // set thresh default
      P = 512;                               // set P default
      T = 512;                               // set T default
      lastBeatTime = sampleCounter;          // bring the lastBeatTime up to date       
      firstBeat = true;                      // set these to avoid noise
      secondBeat = true;                     // when we get the heartbeat back
     }
 
  sei();                                     // enable interrupts when youre done!
}// end isr

As i said, im a newbie and im trying to gain some understanding of how i can bring it together.

Best

[Reply #13 on:]

Yes, that was the missing part, where the magic actually happens. What it is doing is looking for the high spots in the wave form that actually indicate a beat. It computes the time between the last two beats, if there are more than 2 beats detected, and computes a rate based on the time. The last 10 rates are stored in the (global) rate array.

You should be able to simply access the last value in that array to make your decision(s).

[Reply #14 on:]

I've been messing around with it for a while now, but having a hard time understanding how access the function. what i tried now was

Code:

digitalWrite(diffPin,HIGH);
delay(2000);     
digitalWrite(diffPin,LOW);             // turn off pin 13 LED
     }

it's located in the end of the code below, any idea how i can do this?

Code:

//  VARIABLES
int pulsePin = 0;                 // Pulse Sensor purple wire connected to analog pin 0
int diffPin = 7  ;                // pin to blink led at each beat
int fadePin = 13;                  // pin to do fancy classy fading blink at each beat
int fadeRate = 0;                 // used to fade LED on with PWM on fadePin


// these variables are volatile because they are used during the interrupt service routine!
volatile int BPM;                   // used to hold the pulse rate
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // holds the time between beats, the Inter-Beat Interval
volatile boolean Pulse = false;     // true when pulse wave is high, false when it's low
volatile boolean QS = false;        // becomes true when Arduoino finds a beat.


void setup(){
  pinMode(diffPin,OUTPUT);         // pin that will blink to your heartbeat!
  pinMode(fadePin,OUTPUT);          // pin that will fade to your heartbeat!
  Serial.begin(115200);             // we agree to talk fast!
  interruptSetup();                 // sets up to read Pulse Sensor signal every 2mS
   // UN-COMMENT THE NEXT LINE IF YOU ARE POWERING The Pulse Sensor AT LOW VOLTAGE,
   // AND APPLY THAT VOLTAGE TO THE A-REF PIN
   //analogReference(EXTERNAL);   
}



void loop(){
  sendDataToProcessing('S', Signal);     // send Processing the raw Pulse Sensor data
  if (QS == true){                       // Quantified Self flag is true when arduino finds a heartbeat
        fadeRate = 255;                  // Set 'fadeRate' Variable to 255 to fade LED with pulse
        sendDataToProcessing('B',BPM);   // send heart rate with a 'B' prefix
        sendDataToProcessing('Q',IBI);   // send time between beats with a 'Q' prefix
        QS = false;                      // reset the Quantified Self flag for next time   
     }
     
     

 
  ledFadeToBeat();
 
  delay(20);                             //  take a break
}


void ledFadeToBeat(){
    fadeRate -= 15;                         //  set LED fade value
    fadeRate = constrain(fadeRate,0,255);   //  keep LED fade value from going into negative numbers!
    analogWrite(fadePin,fadeRate);          //  fade LED
  }


void sendDataToProcessing(char symbol, int data ){
    Serial.print(symbol);                // symbol prefix tells Processing what type of data is coming
    Serial.println(data);                // the data to send culminating in a carriage return
  }









volatile int rate[10];                    // used to hold last ten IBI values
volatile unsigned long sampleCounter = 0;          // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;           // used to find the inter beat interval
volatile int P =512;                      // used to find peak in pulse wave
volatile int T = 512;                     // used to find trough in pulse wave
volatile int thresh = 512;                // used to find instant moment of heart beat
volatile int amp = 100;                   // used to hold amplitude of pulse waveform
volatile boolean firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = true;       // used to seed rate array so we startup with reasonable BPM


void interruptSetup(){     
  // Initializes Timer2 to throw an interrupt every 2mS.
  TCCR2A = 0x02;     // DISABLE PWM ON DIGITAL PINS 3 AND 11, AND GO INTO CTC MODE
  TCCR2B = 0x06;     // DON'T FORCE COMPARE, 256 PRESCALER
  OCR2A = 0X7C;      // SET THE TOP OF THE COUNT TO 124 FOR 500Hz SAMPLE RATE
  TIMSK2 = 0x02;     // ENABLE INTERRUPT ON MATCH BETWEEN TIMER2 AND OCR2A
  sei();             // MAKE SURE GLOBAL INTERRUPTS ARE ENABLED     
}


// THIS IS THE TIMER 2 INTERRUPT SERVICE ROUTINE.
// Timer 2 makes sure that we take a reading every 2 miliseconds
ISR(TIMER2_COMPA_vect){                         // triggered when Timer2 counts to 124
    cli();                                      // disable interrupts while we do this
    Signal = analogRead(pulsePin);              // read the Pulse Sensor
    sampleCounter += 2;                         // keep track of the time in mS with this variable
    int N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

//  find the peak and trough of the pulse wave
    if(Signal < thresh && N > (IBI/5)*3){       // avoid dichrotic noise by waiting 3/5 of last IBI
        if (Signal < T){                        // T is the trough
            T = Signal;                         // keep track of lowest point in pulse wave
         }
       }
     
    if(Signal > thresh && Signal > P){          // thresh condition helps avoid noise
        P = Signal;                             // P is the peak
       }                                        // keep track of highest point in pulse wave
   
  //  NOW IT'S TIME TO LOOK FOR THE HEART BEAT
  // signal surges up in value every time there is a pulse
if (N > 250){                                   // avoid high frequency noise
  if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){       
    Pulse = true;                               // set the Pulse flag when we think there is a pulse
   // digitalWrite(diffPin,HIGH);                // turn on pin 13 LED
    IBI = sampleCounter - lastBeatTime;         // measure time between beats in mS
    lastBeatTime = sampleCounter;               // keep track of time for next pulse
         
         if(firstBeat){                         // if it's the first time we found a beat, if firstBeat == TRUE
             firstBeat = false;                 // clear firstBeat flag
             return;                            // IBI value is unreliable so discard it
            }   
         if(secondBeat){                        // if this is the second beat, if secondBeat == TRUE
            secondBeat = false;                 // clear secondBeat flag
               for(int i=0; i<=9; i++){         // seed the running total to get a realisitic BPM at startup
                    rate[i] = IBI;                     
                    }
            }
         
    // keep a running total of the last 10 IBI values
    word runningTotal = 0;                   // clear the runningTotal variable   

    for(int i=0; i<=8; i++){                // shift data in the rate array
          rate[i] = rate[i+1];              // and drop the oldest IBI value
          runningTotal += rate[i];          // add up the 9 oldest IBI values
        }
       
    rate[9] = IBI;                          // add the latest IBI to the rate array
    runningTotal += rate[9];                // add the latest IBI to runningTotal
    runningTotal /= 10;                     // average the last 10 IBI values
    BPM = 60000/runningTotal;               // how many beats can fit into a minute? that's BPM!
    QS = true;                              // set Quantified Self flag
    // QS FLAG IS NOT CLEARED INSIDE THIS ISR
    }                       
}

  if (Signal < thresh && Pulse == true){     // when the values are going down, the beat is over
    //  digitalWrite(diffPin,LOW);            // turn off pin 13 LED
      Pulse = false;                         // reset the Pulse flag so we can do it again
      amp = P - T;                           // get amplitude of the pulse wave
      thresh = amp/2 + T;                    // set thresh at 50% of the amplitude
      P = thresh;                            // reset these for next time
      T = thresh;
     }
 
  if (N > 2500){                             // if 2.5 seconds go by without a beat
      thresh = 512;                          // set thresh default
      P = 512;                               // set P default
      T = 512;                               // set T default
      lastBeatTime = sampleCounter;          // bring the lastBeatTime up to date       
      firstBeat = true;                      // set these to avoid noise
      secondBeat = true;                     // when we get the heartbeat back
     }

  if ( (Signal > thresh) && (Pulse == false) && (N > (IBI/5)*3) ){     

digitalWrite(diffPin,HIGH);
delay(2000);     
digitalWrite(diffPin,LOW);           
     }

  sei();                                     // enable interrupts when youre done!
}// end isr