Arduino capacitance meter

This was a simple project which appeared on the ARduino website – https://www.arduino.cc/en/Tutorial/CapacitanceMeter , to look at the theory visit that page. I was wanting to see how accurate this is and also wanted to test this on other variants such as the Chipkit and the MSP_EXP430G2 to compare performance between these development boards

I selected an Arduino Uno for this.

You will need a Breadboard, 10k Resistor, 220 ohm resistor and some hookup wire
Layout

arduino capacitance

Code

[codesyntax lang=”cpp”]

#define analogPin      0          
#define chargePin      13         
#define dischargePin   11        
#define resistorValue  10000.0F   

unsigned long startTime;
unsigned long elapsedTime;
float microFarads;                
float nanoFarads;

void setup()
{
  pinMode(chargePin, OUTPUT);     
  digitalWrite(chargePin, LOW);  
  Serial.begin(9600);             
}

void loop()
{
  digitalWrite(chargePin, HIGH);  
  startTime = millis();
  while(analogRead(analogPin) < 648){       
  }

  elapsedTime= millis() - startTime;
  microFarads = ((float)elapsedTime / resistorValue) * 1000;          

  if (microFarads > 1)
  {
    Serial.print((long)microFarads);       
    Serial.println(" microFarads");         
  }

  else{
    nanoFarads = microFarads * 1000.0;      
    Serial.print((long)nanoFarads);         
    Serial.println(" nanoFarads");          
    delay(500); 
  }

  digitalWrite(chargePin, LOW);            
  pinMode(dischargePin, OUTPUT);            
  digitalWrite(dischargePin, LOW);          
  while(analogRead(analogPin) > 0){         
  }

  pinMode(dischargePin, INPUT);            
}

[/codesyntax]

results

I tested this with several capacitors, one thing I noticed was with a 470uF capacitor the first reading was off, 402uF reported. After that all the readings were about the 470uF mark. In the screen capture above you can see a 226uF reading

I also tested 10uF,  22uf and 47uF capacitors as well and the readings were pretty accurate. You have to factor in that all capacitiors have a level of tolerance