Capacitance_Meter.ino

#include <LiquidCrystal.h>

/*  RCTiming_capacitance_meter
 *   Paul Badger 2008
 *  Modified by Christian Terjesen in May 2013
 */

#define analogPin      0          // analog pin for measuring capacitor voltage
#define chargePin      13         // pin to charge the capacitor - connected to one end of the charging resistor
#define dischargePin   2         // pin to discharge the capacitor
#define resistorValue  10000.0F   // change this to whatever resistor value you are using
                                  // F formatter tells compliler it's a floating point value

unsigned long startTime;
unsigned long elapsedTime;
float microFarads;                // floating point variable to preserve precision, make calculations
float nanoFarads;


LiquidCrystal lcd(12, 11, 10, 9, 8, 7);



void setup(){
  
  lcd.begin(16, 2);
  pinMode(chargePin, OUTPUT);     // set chargePin to output
  digitalWrite(chargePin, LOW);  
  
 

  Serial.begin(9600);             // initialize serial transmission for debugging
}

void loop(){
  digitalWrite(chargePin, HIGH);  // set chargePin HIGH and capacitor charging
  startTime = millis();
  


  while(analogRead(analogPin) < 648){       // 647 is 63.2% of 1023, which corresponds to full-scale voltage 
  }

  elapsedTime= millis() - startTime;
 // convert milliseconds to seconds ( 10^-3 ) and Farads to microFarads ( 10^6 ),  net 10^3 (1000)  
  microFarads = ((float)elapsedTime / resistorValue) * 1000;   
  Serial.print(elapsedTime);       // print the value to serial port
  Serial.print(" mS    ");         // print units and carriage return


  if (microFarads > 1){
    Serial.print((long)microFarads);       // print the value to serial port
    Serial.println(" microFarads");         // print units and carriage return
    lcd.print((long)microFarads);
    lcd.print(" microFarads");
  }
  else
  {
    // if value is smaller than one microFarad, convert to nanoFarads (10^-9 Farad). 
    // This is  a workaround because Serial.print will not print floats

    nanoFarads = microFarads * 1000.0;      // multiply by 1000 to convert to nanoFarads (10^-9 Farads)
    Serial.print((long)nanoFarads);         // print the value to serial port
    Serial.println(" nanoFarads");          // print units and carriage return
    lcd.print((long)nanoFarads);
    lcd.print(" nanoFarads");
  }
  
  {
  // when characters arrive over the serial port...
  if (Serial.available()) {
    // wait a bit for the entire message to arrive
      delay(100);
    // clear the screen
    lcd.clear();
    // read all the available characters
    while (Serial.available() > 0) {
      // display each character to the LCD
      lcd.write(Serial.read());
    }
  }
  }
 
      
        /* dicharge the capacitor  */
  digitalWrite(chargePin, LOW);             // set charge pin to  LOW 
  pinMode(dischargePin, OUTPUT);            // set discharge pin to output 
  digitalWrite(dischargePin, LOW);          // set discharge pin LOW 
  while(analogRead(analogPin) > 0){         // wait until capacitor is completely discharged
  

  pinMode(dischargePin, INPUT);            // set discharge pin back to input

  } 
lcd.clear();


}