Capacitance measurement with the Arduino Uno

Step 1: Capacitance Measurement With the Arduino Uno

There are lots of examples of how to do this on the internet, but I’m going to suggest an incredibly simple way to it. Let’s start with the theory.

arduino code

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;

void setup() { pinMode(OUT_PIN, OUTPUT); //digitalWrite(OUT_PIN, LOW); //This is the default state for outputs pinMode(IN_PIN, OUTPUT); //digitalWrite(IN_PIN, LOW);

Serial.begin(9600); }

void loop() { //Capacitor 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 and print result

float capacitance = (float)val * IN_CAP_TO_GND / (float)(MAX_ADC_VALUE - val);

Serial.print(F("Capacitance Value = ")); Serial.print(capacitance, 3); Serial.print(F(" pF (")); Serial.print(val); Serial.println(F(") "));

while (millis() % 500 != 0) ; }

Thank you