Wie man auf dem oberen Oszilloskop-Bild zudem sehen kann, ist das aufgenommene Signal relativ klein bzw. der Transistor sehr empfindlich, um das schwache Signal aufnehmen zu können.Um ein optimales Ergebnis zu erhalten, empfehlen wir das Modul zum messen so vorzubereiten, wie im folgenden Bild gezeigt:
[[Datei:KY-0039_1.jpg|620x574px|none|620x574px]]
[[Datei:KY-0039_2.jpg|620x517px|none|620x517px]]
==Codebeispiel Arduino==
<pre class="brush:cpp"> //////////////////////////////////////////////////////////////////////// Pulse Monitor Test Scriptint sensorPin = 0;/// Copyright (c)2015 Dan Truongdouble alpha = 0/// Permission is granted to use this software under the MIT/// licence, with my name and copyright kept in source code/// http://http://opensource.75;org/licenses/MITint period = 100;///double change = 0/// KY039 Arduino Heartrate Monitor V1.0;(April 02, 2015)double minval = 0//////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////// @param[in] IRSensorPin Analog pin on which IR detector is connected/// @param[in] delay (msec) delay between calls to this method.0It is/// best to call it at least 5 times per beat, aka/// no slower than 150msec for 70bpm. An ideal value/// is 60ms or faster to handle up to 200 BPM.////// @brief/// True if heartbeat is detected on the sensor./// This code is trivial and just does a peak detection, instead of/// trying to detect the heart's pulse waveform./// Note: I am fudging sensor data with the delay to make the integer/// math after that uses constants, somewhat independant of the sleep/// delay used in the main loop. Otherwise if maxValue decays too slow/// or too fast, it causes glitches and false beat detection.////////////////////////////////////////////////////////////////////////#define HBDEBUG(i) i//#define HBDEBUG(i)int rawValue;void setup boolheartbeatDetected(int IRSensorPin, int delay)
{
static int maxValue = 0; static bool isPeak = false; HBDEBUG(Serial.begin print(9600maxValue); Serial.print("xp, ")); bool result = false; rawValue = analogRead(IRSensorPin); // Separated because analogRead() may not return an int rawValue *= (1000/delay); HBDEBUG(Serial.print(isPeak); Serial.print("p, ")); HBDEBUG(Serial.print(rawValue); Serial.print("r, ")); HBDEBUG(Serial.print(maxValue); Serial.print("m, ")); // If sensor shifts, then max is out of whack. // Just reset max to a new baseline. if (rawValue * 4L < maxValue) { maxValue = rawValue * 0.8; HBDEBUG(Serial.print("RESET, ")); rawValue = rawValue *4L; HBDEBUG(Serial.print(rawValue); Serial.print("rw, ")); } // Detect new peak if (rawValue > maxValue - (1000/delay)) { // Only change peak if we find a higher one. if (rawValue > maxValue) { maxValue = rawValue; } // Only return true once per peak. if (isPeak == false) { result = true; HBDEBUG(Serial.print(result); Serial.print(", *")); } isPeak = true; } else if (rawValue < maxValue - (3000/delay)) { isPeak = false; // Decay max value to adjust to sensor shifting // Note that it may take a few seconds to re-detect // the signal when sensor is pushed on meatier part // of the finger. Another way would be to track how // long since last beat, and if over 1sec, reset // maxValue, or to use derivatives to remove DC bias. maxValue-=(1000/delay); } HBDEBUG(Serial.print("\n")); return result;
}
////////////////////////////////////////////////////////////////////////// Arduino main code////////////////////////////////////////////////////////////////////////int ledPin=13;int analogPin=0; void loop setup()
{
static double oldValue = 0 // Built-in arduino board pin for the display LED pinMode(ledPin,OUTPUT); static double oldChange = 0 // Init serial console Serial.begin(9600); Serial.println("Heartbeat detection sample code.");}
const int rawValue delayMsec = analogRead (sensorPin); double value = alpha * oldValue + (1 - alpha) * rawValue60;// 100msec per sample
Serial// The main loop blips the LED and computes BPMs on serial port.print void loop(rawValue){ static int beatMsec = 0; Serial.print (",") int heartRateBPM = 0; Serial.println (valuerawValue); if (heartbeatDetected(analogPin, delayMsec)) { oldValue heartRateBPM = value60000 / beatMsec; digitalWrite(ledPin,1);
// Print msec/beat and instantaneous heart rate in BPM Serial.print(rawValue); Serial.print(", "); Serial.println(heartRateBPM); beatMsec = 0; } else { digitalWrite(ledPin,0); } // Note: I assume the sleep delay is way longer than the // number of cycles used to run the code hence the error // is negligible for math. delay (perioddelayMsec); beatMsec += delayMsec;
}
</pre>