Boa dia meus caros. É o seguinte, estou aqui com algumas dúvidas relativamente a um código sobre um sensor de pulsação, fui desenvolvendo o código com ajuda da net e cheguei à conclusão de que tenho de substituir por um potenciómetro (se der) ou então fazer uma função para detectar se a pulsacao ja esta calibrada para iniciar um outro sistema. Isto porque?
No resto do trabalho, dependendo do valor do batimento cardiaco obtido pelo sensor, tenho de activar uma bomba. Imaginemos que o valor é abaixo de 50bpm e a bomba tem de ser activada. O meu problema é que com o sensor de pulsação, primeiro que aquilo calibre bem a pulsação real, aquilo anda com os valores para cima e para baixo desde 0 até 200 durante uns segundos, o que faria com que activasse logo a bomba e isso não quero.
Já tentei meter isto com um potenciómetro, mas não estou a conseguir fazer nada. Dá-me sempre o valor de zero.
Vou deixar aqui o código que tenho, para se alguém me conseguir ajudar.

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
int pulsePin = 0;                                // Pulse Sensor purple wire connected to analog pin 0
int blinkPin = 11;                       // 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
int ledsinal = 8;

// 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 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! AQUI
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


void setup(){
pinMode(blinkPin,OUTPUT);                // pin that will blink to your heartbeat!
pinMode(fadePin,OUTPUT);                 // pin that will fade to your heartbeat!
pinMode(ledsinal,OUTPUT);
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(){

ledFadeToBeat();
led();
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
}

int led() {

if (BPM1 > 70) {
digitalWrite(ledsinal, HIGH);}
else{

         digitalWrite(ledsinal, LOW);}}