Fluctuating voltage value in print console

Projects Programming
15

I just want to make my own code work and understand that before i try other codes.

When i start the serial monitor the voltage shows correct smooth and fine the first seconds. But after some seconds, its begin to fluctuate by approx 0.1V.

I hvae mounted an 10uF electrolytic capacitor between ground and analog input, but that does not smooth out the readings. But when i adjust the input voltage i can se the values change more slowly. But it does not fix the voltage readings.

But why does the voltage sows nice and smooth for some seconds when i start the serial monitor and resets the board?

This is my last code:

int voltPin = A0;


void setup() {
  Serial.begin(9600);
  pinMode(voltPin, INPUT);

}

void loop() {

  int numReads = 5;
  int senseSum = 0;

  for (int k = 0; k < numReads; k++) {
    senseSum += analogRead(voltPin);
    delay(1);
  }

  int senseAve = senseSum / numReads;
  float voltage = senseAve * (17.1 / 1023.0);
  Serial.print("Battery Voltage: ");
  Serial.print(voltage);
  Serial.println("V");
  delay(100);
}