Knob Reading to Volts

Part of the Inputs section of Coddy's Arduino journey. Lesson 9 of 22.

A reading of 1023 means 5V, so each step is 5 / 1023 of a volt. Multiply to turn a reading into volts:

int reading = analogRead(A0);
float volts = reading * 5.0 / 1023.0;
Serial.println(volts);

The decimal points matter. reading * 5 / 1023 uses only whole numbers, so it is integer division and drops the fraction: a reading of 512 gives 2, not 2.5. 5.0 makes the math keep its decimals.

The order matters too: reading / 1023 * 5.0 divides two whole numbers first, which is 0 for every reading below 1023.

Serial.println() shows a float with two decimals, like 2.50.

Challenge

Easy

The knob is on A0. Print the voltage on the pin:

read A0 into an int
turn it into volts in a float: reading * 5.0 / 1023.0
print the volts, then wait 100 ms

Press Run, turn the knob, then Check.

Try it yourself

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

void loop() {
  int reading = analogRead(A0);
  // turn the reading into volts, print them, wait 100 ms
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Inputs

Practice on your own: Arduino playground