Heartbeat/pulse monitor:

• Arduino project to detect/measure pulse/heartbeat rate
  ----------------------------

• code from some online site:
  
  int sensorPin = A0;
  int ledPin = 13; // Or any other digital pin for visualization
  int sensorValue = 0;
  int threshold = 550; // Adjust this threshold based on your sensor and setup
  unsigned long startTime = 0;
  unsigned long endTime = 0;
  int pulseCount = 0;
  float beatsPerMinute = 0;
  float smoothingFactor = 0.3; // Adjust for smoothing
  float smoothedBPM = 0;

  void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  }

  void loop() {
  sensorValue = analogRead(sensorPin);

  if (sensorValue > threshold) {
  digitalWrite(ledPin, HIGH);
  if (startTime == 0) {
  startTime = millis();
  }
  } else {
  digitalWrite(ledPin, LOW);
  if (startTime != 0) {
  endTime = millis();
  pulseCount++;
  unsigned long pulseInterval = endTime - startTime;
  startTime = 0;

  if (pulseInterval > 100) { // Filter out very short intervals (noise)
  beatsPerMinute = 60000.0 / pulseInterval;
  smoothedBPM = (smoothingFactor * beatsPerMinute) + ((1.0 - smoothingFactor) * smoothedBPM);
  Serial.print("BPM: ");
  Serial.println(smoothedBPM);
  }
  }
  }
  delay(1); // Small delay to avoid excessive readings
  }

  -----------------------------

• Links/refs:
  • click bait: relevant short uses KY039 sensor, but you can't hardly get to it:
    https://www.youtube.com/shorts/g97hQr93V7U
  • so-so, strong accent, locked up 4600 - https://www.youtube.com/watch?v=hPzJdDlBiQ0
  • good, measures change in IR as transmitted completely through fingertip, from nail to finger pad:
    https://projecthub.arduino.cc/yashastronomy/diy-infrared-heart-beat-sens...
  • very good, detailed circuit analysis - https://www.instructables.com/Simple-DIY-Pulse-Sensor/
  • seems ok, uses the "pulsesensor" - https://lastminuteengineers.com/pulse-sensor-arduino-tutorial/
  • https://www.circuitmagic.com/arduino/heartbeat-sensor-module-with-arduin...
  • https://forum.arduino.cc/t/homemade-pulse-sensor-for-detecting-hartbeat/...
  • https://www.hackster.io/eguidezhan/heartbeat-sensor-based-on-arduino-uno...
  • https://www.robot-italy.com/en/infrared-emitters-and-detectors.html
  • https://makezine.com/projects/ir-pulse-sensor/
  • uses KY-039 sensor, with IR transmitted through the fingertip. simple, well-done - https://projecthub.arduino.cc/Johan_Ha/from-ky-039-to-heart-rate-8c660b

eof