Description: The Tell Tale Heart Box was my small diorama rendition of an intense scene from Edgar Allen Poe’s short story. It essentially uses the pulse sensor to generate your heart beat and apply it to a solenoid that pushes the floor board up and down (simulating a live pulse and recreating the paranoia felt by the story’s protagonist that in turn causes him to turn himself in to the authorities stopping by his home).
Heart Box uses:
-Pulse Sensor (glued on the backside and ready for use on the back side of the box).
-Solenoid (glued in the center of the box for vertical stance with a floor board glued to the pin).
-3 9V batteries (2 for the solenoid/1 for the Arduino board)
- Bread Board/Arduino Uno/Jumper Cables etc.
more photos coming…
NOTE: I lucked out with this project because the pulse sensor code runs off of one pin to begin with. I simply hooked the solenoid to that pin and had it working from the beginning. That said, the vast majority of this code is the work of Yury Gitman and Joel Murphy and has nothing to do with me.
-Josef
/*
This program reads data from the Pulse Sensor.
Serial output is designed to mate with Processing sketch “P_PulseSensor_xx” series
Serial Protocol initiates datastring with coded ascii character, ends each message with carriage return
We named the variable that holds the heart rate (BPM) after the group Quantified Self.
They backed our Kickstarter campaing at the $600 level and having a variable named after them is one of their rewards.
Go Count Yourself!!! http://quantifiedself.com/
by Joel Murphy & Yury Gitman in Brooklyn, Summer 2011.
*/
// VARIABLES
unsigned long time; // Holds current time for pulse rate calculation
unsigned long lastTime; // Used for calculating time between beats
int Sensor; // Holds current analog Sensor Reading
int lastSensor; // Used to find waveform direction
int Peak; // Holds value of peak in waveform
int Trough; // Holds value of trough in waveform
int beats[10]; // Array to collect time between beats for calculating BPM
int beatCounter = 0; // Used to hold position in beats array
int QuantifiedSelf; // Used to hold the heart rate value (BPM)
int drop; // Holds the amplitude of waveform
int fadeRate = 10; // when arduino finds a heartbeat, it will fade an LED on pin 11 (PWM)
int Fade = 0; // Fade variable will set PWM
boolean falling = false; // used to keep track of waveform direction
// PINS
int LED = 13; // pin 13 – solenoid
int dimLED = 11; // LED on pin 11 fades with each pulse
int PulseSensor = 5; // Pulse Sensor purple wire connected to analog pin 5
void setup()
{
pinMode(LED, OUTPUT); // set the LED pins as outputs
pinMode(dimLED, OUTPUT);
Serial.begin(115200); // start the hardware serial block and set the baud rate
lastTime = millis(); // initialize lastTime variable
}
void loop()
{
Sensor = analogRead(PulseSensor); // take a reading
Serial.print(“s”); // send raw analog data to Processing sketch (or other)
Serial.println(Sensor); // ‘s’ = Raw Sensor Data
// USE WITH LED ON PIN 11 FOR FADE EFFECT
Fade -= fadeRate; // Fade variable set to 255 when heart beat is found
Fade = constrain(Fade,0,255); // these lines fade the LED
analogWrite(dimLED,Fade);
// KEEP TRACK OF THE DIRECTION OF THE WAVEFORM
if (falling == false){ // if the sensor values are rising
if (Sensor lastSensor){ // otherwise, if current reading is bigger, values are still rising
Peak = Sensor; // record the next potential peak
lastSensor = Sensor; // keep track of rising signal
}
}
if (falling == true){ // if the sensor values are falling
if (Sensor > lastSensor){ // if current reading is bigger than last reading
falling = false; // a trough has been reached
Serial.print(“T”); // send trough value to Processing sketch (or other)
Serial.println(Trough); // ‘T’ = Trough in waveform
drop = Peak – Trough; // difference = signal amplitude
Peak = 0; // setting Peak to 0 here helps get rid of noise
// THIS IF STATEMENT IS HOW THE HEARTBEAT IS FOUND IN PULSE SENSOR WAVEFORM
if (drop > 4 && drop <60){ // ignore noise in signal. adjust as needed
timeBeat(); // go work out the BPM
Serial.print("d"); // send the amplitude to Processing Sketch (or other)
Serial.println(drop); // 'd' = amplitude of waveform
digitalWrite(LED,HIGH); // start pin 13 LED blink
Fade = 255; // set fading LED to high brightness
}
}else if (Sensor < lastSensor){ // otherwise, if current reading is smaller weʻre still falling
Trough = Sensor; // record the next potential trough
lastSensor = Sensor; // keep track of falling signal
}
}
delay(20); // break for 20mS. Processing frame-rate = 100.
}// END VOID LOOP
void timeBeat(){
time = millis(); // take note of the current time
beats[beatCounter] = time – lastTime; // record miliseconds since the last pulse in beats array
lastTime = time; // stay up to date!
beatCounter ++; // move array pointer to next position in array
if (beatCounter == 10){ // if we've taken 10 readings, it's time to derive heart rate
QuantifiedSelf = getBPM(); // go derive the heart rate
Serial.print("q"); // send the heart rate to Processing sketch (or other)
Serial.println(QuantifiedSelf); // 'q' = heart rate
beatCounter = 0;
}
}// END OF timeBeat FUNCTION
// This function will return a value for heart rate (Beats Per Minute)
int getBPM(){
int dummy; // used in sorting
int mean; // used in averaging
boolean done = false; // clear sorting flag
// this simple sorting routine will arrange values in the beat array from lowest to highest
while(done != true){
done = true;
for (int j=0; j beats[j + 1]){ // sorting numbers here
dummy = beats[j + 1];
beats [j+1] = beats[j] ;
beats[j] = dummy;
done = false;
}
}
}
// this FOR loop selects the longer beat time values to avoid incorrect heart rate readings
for(int k=1; k<9; k++){ // exclude lowest and highest values from averaging
mean += beats[k]; // add beat times together
}
mean /=8; // averaging
mean = 60000/mean; // devide 60 seconds by average pulse length
return mean; // return beats per minute
}// END OF getBPM function
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