Analog Input: Reading a Potentiometer

Read a smoothly-adjustable knob into your sketch using analogRead — the practical, coded version of Lesson 29's ADC theory.

You'll need: a potentiometer (10kΩ is typical), jumper wires, a breadboard, and your Uno.

Wire the potentiometer's two outer legs to 5V and GND, and its middle wiper leg to analog pin A0 — the same three-terminal wiring as the dimmer build in Lesson cb-07, just feeding a microcontroller's analog input instead of an LED branch directly.

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

void loop() {
  int sensorValue = analogRead(A0);
  Serial.println(sensorValue);
  delay(100);
}

analogRead(A0) triggers the Uno's built-in ADC (Lesson 29) to measure the voltage at A0 and returns a number from 0 to 1023 — the Uno's ADC is 10-bit, exactly matching that lesson's example. Turning the knob fully one way should read close to 0; fully the other way, close to 1023.

Serial.begin(9600) and Serial.println() are covered properly in Lesson ard-09, but a quick preview here: they let the board send text back to your computer, viewable in the IDE's Serial Monitor (Tools → Serial Monitor), which is the easiest way to actually watch these changing numbers as you turn the knob.