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### Topic: How to measure the voltage peak from pulse sensor? (Read 2198 times)previous topic - next topic

#### mentaikosauceboy

##### Jan 24, 2020, 10:00 am
So my project requires me to find the voltage peak from the pulse sensor.

1) How can i measure my voltage peak(The highest amplitude from the graph)

2)How can i take the average value of the Voltage peak?
Lets just say,there are 10 peaks in this waveform.

I am using Arduino Uno and Pulse sensor for heart rate.

Really appreciate if anyone can help me out!

#### mentaikosauceboy

#1
##### Jan 25, 2020, 01:16 pm
Hi all,how can i collect my voltage peak with my sensor?

The attached is the graph from serial plotter.

My requirement in code is to collect the average voltage peak for every 10 seconds or so.

#### UKHeliBob

#2
##### Jan 25, 2020, 01:42 pm
Topics merged

Why did you start a new topic on the same subject ?
Please do not send me PMs asking for help.  Post in the forum then everyone will benefit from seeing the questions and answers.

#### Idahowalker

#3
##### Jan 25, 2020, 02:18 pm
int someHighestValue = 0;

int some NewValue = 0;

if NewValue > someHighestValue then someHighestValue = NewValue.

#### mentaikosauceboy

#4
##### Jan 25, 2020, 03:50 pm
How can i measure my peak voltage then?

#### Idahowalker

#5
##### Jan 25, 2020, 04:17 pm
Well, you could hook the signal up to the Analog To Digital converter pin on the Uno, sample the signal and then do the thing.

#### ballscrewbob

#6
##### Jan 25, 2020, 04:20 pm
@mentaikosauceboy

Other post/duplicate DELETED
Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.
Continued cross posting could result in a time out from the forum.

Could you take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google (who would have thunk it ! ) or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

#### Idahowalker

#7
##### Jan 25, 2020, 06:41 pm
The attached is the graph from serial plotter.

My requirement in code is to collect the average voltage peak for every 10 seconds or so.

Have you done anything with the millis() function? There is a lot of information on this site about millis()

#### gilshultz

#8
##### Jan 26, 2020, 02:48 am
You need a peak detector circuit that integrates the signal so you can read it with the A/D. Below is a simple one. The capacitor controls how long the sample will survive, the resistor discharges the capacitor. The combination of RC will allow you to adjust the sample to what you want.

There are a lot of on line Peak Detector information. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

#### mentaikosauceboy

#9
##### Jan 28, 2020, 06:10 pmLast Edit: Jan 28, 2020, 06:17 pm by mentaikosauceboy
Hi all thankyou for your kind replies..

I am currently using this code.. How can i go about collecting my max and min vals.. using threshold as I am collecting heart-rate signals/pulse.. and also the MAX and MIN values..!

Code: [Select]

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

//  Variables
int pulsePin = A0;
int voltagePeak = 0;

// Volatile Variables, used in the interrupt service routine!
volatile int BPM;                   // int that holds raw Analog in 0. updated every 2mS
volatile int Signal;                // holds the incoming raw data
volatile int IBI = 600;             // int that holds the time interval between beats! Must be seeded!
volatile boolean Pulse = false;     // "True" when User's live heartbeat is detected. "False" when not a "live beat".
volatile boolean QS = false;        // becomes true when Arduoino finds a beat.

// Regards Serial OutPut  -- Set This Up to your needs
static boolean serialVisual = true;   // Set to 'false' by Default.  Re-set to 'true' to see Arduino Serial Monitor ASCII Visual Pulse

volatile int rate[10];                      // array to hold last ten IBI values
volatile unsigned long sampleCounter = 0;          // used to determine pulse timing
volatile unsigned long lastBeatTime = 0;           // used to find IBI
volatile int P = 512;                      // used to find peak in pulse wave, seeded
volatile int T = 512;                     // used to find trough in pulse wave, seeded
volatile int thresh = 525;                // used to find instant moment of heart beat, seeded
volatile int amp = 100;                   // used to hold amplitude of pulse waveform, seeded
volatile boolean firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
volatile boolean secondBeat = false;      // used to seed rate array so we startup with reasonable BPM

void setup()
{
Serial.begin(115200);             // we agree to talk fast!
lcd.begin(16,2);
lcd.print("Extracting...");
lcd.setCursor(0,0);
lcd.print("Extracting...");
interruptSetup();                 // sets up to read Pulse Sensor signal every 2mS
// IF YOU ARE POWERING The Pulse Sensor AT VOLTAGE LESS THAN THE BOARD VOLTAGE,
// UN-COMMENT THE NEXT LINE AND APPLY THAT VOLTAGE TO THE A-REF PIN
//   analogReference(EXTERNAL);
}

//  Where the Magic Happens
void loop()
{
serialOutput();

if (QS == true) // A Heartbeat Was Found
{
// BPM and IBI have been Determined
// Quantified Self "QS" true when arduino finds a heartbeat
serialOutputWhenBeatHappens(); // A Beat Happened, Output that to serial.
QS = false; // reset the Quantified Self flag for next time
}

delay(20); //  take a break
}

{
}

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
}

void serialOutput()
{   // Decide How To Output Serial.
if (serialVisual == true)
{
arduinoSerialMonitorVisual('-', Signal);   // goes to function that makes Serial Monitor Visualizer
}
else
{
sendDataToSerial('S', Signal);     // goes to sendDataToSerial function
}
}

void serialOutputWhenBeatHappens()
{
if (serialVisual == true) //  Code to Make the Serial Monitor Visualizer Work
{
voltagePeak = P;
//Serial.print("*** Heart-Beat Happened *** ");  //ASCII Art Madness
Serial.print("BPM: ");
Serial.println(BPM);
//lcd.setCursor (0,1);
Serial.print("Voltage Peak");
Serial.println(voltagePeak);
lcd.setCursor(16,2);
lcd.print("BPM: ");
lcd.println(BPM);
lcd.clear();
lcd.setCursor(0, 1);
lcd.print("Voltage Peak:");
lcd.println(voltagePeak);
}
else
{
sendDataToSerial('B',BPM);   // send heart rate with a 'B' prefix
sendDataToSerial('Q',IBI);   // send time between beats with a 'Q' prefix
}
}

void arduinoSerialMonitorVisual(char symbol, int data )
{
const int sensorMin = 0;      // sensor minimum, discovered through experiment
const int sensorMax = 1024;    // sensor maximum, discovered through experiment
int sensorReading = data; // map the sensor range to a range of 12 options:
int range = map(sensorReading, sensorMin, sensorMax, 0, 11);
// do something different depending on the
// range value:
switch (range)

void sendDataToSerial(char symbol, int data )
{
Serial.print(symbol);
Serial.println(data);
}

ISR(TIMER2_COMPA_vect)
{
cli();
sampleCounter += 2;
int N = sampleCounter - lastBeatTime;

if(Signal < thresh && N > (IBI/5)*3)
{
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;
}

//  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;
IBI = sampleCounter - lastBeatTime;
lastBeatTime = sampleCounter;

if(secondBeat)
{
secondBeat = false;
for(int i=0; i<=9; i++)
{
rate[i] = IBI;
}
}

if(firstBeat)
{
firstBeat = false;
secondBeat = true;
sei();
return;
}
// keep a running total of the last 10 IBI values
word runningTotal = 0;

for(int i=0; i<=8; i++)
{                // shift data in the rate array
rate[i] = rate[i+1];
runningTotal += rate[i];
}

rate[9] = IBI;
runningTotal += rate[9];
runningTotal /= 10;
BPM = 60000/runningTotal;
QS = true;
// QS FLAG IS NOT CLEARED INSIDE THIS ISR
}
}

if (Signal < thresh && Pulse == true)
{
Pulse = false;
amp = P - T;
thresh = amp/2 + T;
P = thresh;
T = thresh;
}

if (N > 2500)
{
thresh = 512;
P = 512;
T = 512;
lastBeatTime = sampleCounter;
firstBeat = true;
secondBeat = false;
}

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