arduino-voltmeter

arduino-voltmeter.ino

long readVcc() 
{ 
  long result; 
  // Read 1.1V reference against AVcc 
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1); 
  delay(2); // Wait for Vref to settle 
  ADCSRA |= _BV(ADSC); // Convert 
  while (bit_is_set(ADCSRA,ADSC)); 
  result = ADCL; 
  result |= ADCH<<8; 
  result = 1126400L / result; // Back-calculate AVcc in mV 
  return result; 
}

const int analogIn = A0;
double avgVoltage = 0;
double Voltage = 0;
int RawValue= 0;

void setup() 
{ 
  Serial.begin(9600);
}

void loop() 
{ 
  Serial.print("Vcc = ");
  Serial.print(readVcc());
  Serial.print(" mV \t");
  RawValue = analogRead(analogIn);
  Voltage = ((RawValue / 1023.0) * readVcc()) / 1000;
  avgVoltage = Voltage / 1.025;
  Serial.print("Measured voltage = ");
  Serial.print(avgVoltage,2); 
  Serial.println(" V");
  delay (1000);
}