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// temp variables
// which analog pin to connect
#define THERMISTORPIN A0
// resistance at 25 degrees C
#define THERMISTORNOMINAL 10000
// temp. for nominal resistance (almost always 25 C)
#define TEMPERATURENOMINAL 25
// how many samples to take and average, more takes longer
// but is more 'smooth'
#define NUMSAMPLES 5
// The beta coefficient of the thermistor (usually 3000-4000)
#define BCOEFFICIENT 3950
// the value of the 'other' resistor
#define SERIESRESISTOR 10000
int samples[NUMSAMPLES];
// conductivity variables
long pulseCount = 0; //a pulse counter variable
unsigned long pulseTime,lastTime, duration, totalDuration;
int samplingPeriod=2; // the number of seconds to measure 555 oscillations
int fivefivefive = 13; // the pin that powers the 555 subcircuit
void setup()
{
Serial.begin(9600);
pinMode(fivefivefive, OUTPUT);
}
void loop()
{
uint8_t i;
float average;
delay(1000); // imagine riffle is doing other stuff (like sleeping)
// now make a conductivity measurement
// temperature ---------------------------------------------
// take N samples in a row, with a slight delay
for (i=0; i< NUMSAMPLES; i++) {
samples[i] = analogRead(THERMISTORPIN);
delay(10);
}
// average all the samples out
average = 0;
for (i=0; i< NUMSAMPLES; i++) {
average += samples[i];
}
average /= NUMSAMPLES;
// convert the value to resistance
average = 1023 / average - 1;
average = SERIESRESISTOR / average;
//Serial.print("Thermistor resistance ");
//Serial.println(average);
float steinhart;
steinhart = average / THERMISTORNOMINAL; // (R/Ro)
steinhart = log(steinhart); // ln(R/Ro)
steinhart /= BCOEFFICIENT; // 1/B * ln(R/Ro)
steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
steinhart = 1.0 / steinhart; // Invert
steinhart -= 273.15; // convert to C
//Serial.print(steinhart);
//Serial.println(" *C");
// conductivity --------------------------------------
//turn on the 555 system
digitalWrite(fivefivefive,HIGH); //turns on the 555 timer subcircuit
pulseCount=0; //reset the pulse counter
totalDuration=0; //reset the totalDuration of all pulses measured
attachInterrupt(1,onPulse,RISING); //attach an interrupt counter to interrupt pin 1 (digital pin #3) -- the only other possible pin on the 328p is interrupt pin #0 (digital pin #2)
pulseTime=micros(); // start the stopwatch
delay(samplingPeriod*1000); //give ourselves samplingPeriod seconds to make this measurement, during which the "onPulse" function will count up all the pulses, and sum the total time they took as 'totalDuration'
detachInterrupt(1); //we've finished sampling, so detach the interrupt function -- don't count any more pulses
//turn off the 555 system
digitalWrite(fivefivefive,LOW);
if (pulseCount>0) { //use this logic in case something went wrong
double durationS=totalDuration/double(pulseCount)/1000000.; //the total duration, in seconds, per pulse (note that totalDuration was in microseconds)
// print out stats
/*Serial.print("sampling period=");
Serial.print(samplingPeriod);
Serial.print(" sec; #pulses=");
Serial.print(pulseCount);
Serial.print("; duration per pulse (sec)=");
*/
// print conductivity value
Serial.print(durationS,4);
Serial.print(", ");
Serial.println(steinhart);
}
}
void onPulse()
{
pulseCount++;
//Serial.print("pulsecount=");
//Serial.println(pulseCount);
lastTime = pulseTime;
pulseTime = micros();
duration=pulseTime-lastTime;
totalDuration+=duration;
//Serial.println(totalDuration);
}
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