the code of Finger Measuring Heartbeat Sensor Module for Ard

 KY-039 Finger Measuring Heartbeat Sensor Module for Arduino(http://www.icstation.com/product_info.php?products_id=3276)
Description
Phototransistor on the other side of the finger, phototransistor used to obtain the flux emitted, when the blood pressure pulse by the finger when the resistance of the phototransistor will be slight changed.

We chose a very high resistance resistor R1, because most of the light through the finger is absorbed,it is desirable phototransistor sensitive enough.Resistance can be selected by experiment to get the best results.
The most important is to keep the shield stray light into the phototransistor. For home lighting that is particularly important because the lights at home mostly based 50HZ or 60HZ fluctuate, so faint heartbeat will add considerable noise.

ARDUINO test code:
// Pulse Monitor Test Script
int ledPin = 13;
int sensorPin = 0;
double alpha = 0.75;
int period = 20;
double change = 0.0;
void setup ()
{
pinMode (ledPin, OUTPUT);
Serial.begin (115200);
}
void loop ()
{
static double oldValue = 0;
static double oldChange = 0;
int rawValue = analogRead (sensorPin);
double value = alpha * oldValue + (1 - alpha) * rawValue;

Serial.print (rawValue);
Serial.print (",");
Serial.println (value);
oldValue = value;
delay (period);
}

http://www.icstation.com/product_info.php?products_id=3276