Knob Dimmer

Part of the Outputs section of Coddy's Arduino journey. Lesson 5 of 24.

A knob gives analogRead() a number from 0 to 1023, and analogWrite() wants 0 to 255. The two ranges do not match, so convert one into the other with map():

int reading = analogRead(A0);
int brightness = map(reading, 0, 1023, 0, 255);
analogWrite(9, brightness);

Knob down gives 0 and the LED is off; knob up gives 1023, which becomes 255, fully on. Every position in between gives a brightness in between.

Writing the reading straight to the LED does not work: analogWrite() only takes 0 to 255, so a reading like 600 comes out as the wrong brightness.

Challenge

Easy

The knob is on A0 and the LED on pin 9. Make the knob set the brightness:

read the knob
turn the reading into 0 to 255 with map()
write it to the LED, then wait 10 ms

Press Run and turn the knob, then Check.

Try it yourself

const int knobPin = A0;
const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // read the knob, map it to 0..255 and write it to the LED
}

Test yourself

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

All lessons in Outputs

Practice on your own: Arduino playground