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The updated Arduino sketch follows:
#include <EEPROM.h>
const int OUT_PIN = A2;
const int IN_PIN = A0;
//Capacitance between IN_PIN and Ground
//Stray capacitance is always present. Extra capacitance can be added to
//allow higher capacitance to be measured.
const float IN_STRAY_CAP_TO_GND = 24.48; //initially this was 30.00
const float IN_EXTRA_CAP_TO_GND = 0.0;
const float IN_CAP_TO_GND = IN_STRAY_CAP_TO_GND + IN_EXTRA_CAP_TO_GND;
const int MAX_ADC_VALUE = 1023;
//averaging setup
const int numReadings = 10; //the number of readings to be averaged
int readings[numReadings]; // the readings from the analog input
int index = 0; // the index of the current reading
int total = 0; // the running total
int average = 0; // the average
//Bargraph setup
const int ledCount = 10; // the number of LEDs in the bar graph
const int led1 = 2;
const int led2 = 3;
int ledPins[] = {
led1, led2, 4, 6, 7,8,9,10,11, 12 }; // an array of pin numbers to which LEDs are attached
int calLowPin = A4; // use 10k pullup resistor with momentary
int calHiPin = A5; // switch to ground
int calLow = 0;
int calHi = 0;
int calLowVal = 40; // approx range of probe empty
int calHiVal = 80; // to full in pfd
int calSwitch = 5;
void setup()
{
pinMode(calLowPin, INPUT);
pinMode(calHiPin, INPUT);
// initialize all the readings to 0:
for (int thisReading = 0; thisReading < numReadings; thisReading++)
readings[thisReading] = 0;
pinMode(OUT_PIN, OUTPUT);
//digitalWrite(OUT_PIN, LOW); //This is the default state for outputs
pinMode(IN_PIN, OUTPUT);
//digitalWrite(IN_PIN, LOW);
pinMode(calSwitch, OUTPUT);
// loop over the led pin array and set them all to output:
for (int thisLed = 0; thisLed < ledCount; thisLed++) {
pinMode(ledPins[thisLed], OUTPUT);
}
Serial.begin(9600);
}
void loop(){
calLow = digitalRead(calLowPin);
calHi = digitalRead(calHiPin);
//Capacitor(Probe) under test between OUT_PIN and IN_PIN
//Rising high edge on OUT_PIN
pinMode(IN_PIN, INPUT);
digitalWrite(OUT_PIN, HIGH);
int val = analogRead(IN_PIN);
//Clear everything for next measurement
digitalWrite(OUT_PIN, LOW);
pinMode(IN_PIN, OUTPUT);
//Calculate result
float capacitance = (float)val * IN_CAP_TO_GND / (float)(MAX_ADC_VALUE - val);
int sensorval = capacitance;
// subtract the last reading:
total= total - readings[index];
// read from the sensor:
readings[index] = sensorval; //average routine
// add the reading to the total:
total= total + readings[index];
// advance to the next position in the array:
index = index + 1;
// if we're at the end of the array...
if (index >= numReadings)
// ...wrap around to the beginning:
index = 0;
// calculate the average:
average = total / numReadings;
// send it to the computer as ASCII digits
delay(1); // delay in between reads for stability
// read the sensor:
int sensorReading = average;
// map the result to a range from 0 to the number of LEDs:
int ledLevel = map(sensorReading, calLowVal, calHiVal, 0, ledCount);
if (calLow == LOW) { //take empty tank cal reading
digitalWrite(calSwitch, HIGH);
calLowVal = average;
EEPROM.update(0, calLowVal);} //save empty calibration result
else {
digitalWrite(calSwitch, LOW);
}
if (calHi == LOW) { //take full tank cal reading
digitalWrite(calSwitch, HIGH);
calHiVal = average;
EEPROM.update(1, calHiVal);} //save full calibration result
else {
digitalWrite(calSwitch, LOW);
}
// loop over the LED array:
for (int thisLed = 0; thisLed < ledCount; thisLed++) {
// if the array element's index is less than ledLevel,
// turn the pin for this element on:
if (thisLed < ledLevel) {
digitalWrite(ledPins[thisLed], HIGH); // High for transistor input
} // low for low current display
// turn off all pins higher than the ledLevel:
else {
digitalWrite(ledPins[thisLed], LOW); // Low for transistor input
} //High for low current display
if (digitalRead(led1) == 1 && digitalRead(led2) == 0) {
digitalWrite (led1, LOW); //Blink bottom led if it's //Low for xstr input
delay (200); //the only one lit
digitalWrite (led1, HIGH); //High for xstr input
delay (200);
}
}
/*Serial.print("Capacitance Value = ");
Serial.print(sensorval);
Serial.println(" pF ");
Serial.print(" Calibration Low = "); //for debug
Serial.print(calLowVal); //comment out for final upload
Serial.println(" pF ");
Serial.print("Calibration High = ");
Serial.print(calHiVal);
Serial.println(" pF ");*/
while (millis() % 500 != 0);
calLowVal = EEPROM.read(0); //values needed if system was powered
calHiVal = EEPROM.read(1); //down
if (EEPROM.read(0) == 255) { //if new chip
EEPROM.write(0, 40); //approx empty reading of probe
}
if (EEPROM.read(1) == 255) {
EEPROM.write(1, 80); // approx full reading of probe
}
}