Potentiometer: analogRead to PWM

Why it’s here

Scale an analog reading into a PWM output.

How it works

The 10-bit input spans 0–1023, while PWM spans 0–255. Integer division by four maps the first range to the second. PWM changes the proportion of time spent HIGH, not the HIGH voltage itself.

Try it

1. Open this experiment
2. Run the example. Set the input to 0, 512 and 1023, and compare each reading with the PWM value and LED brightness.

Connections

• A0 — Potentiometer wiper
• 5V / GND — Potentiometer ends
• D9 ~ — LED through resistor

Example sketch

void setup() {
  pinMode(9, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int reading = analogRead(A0);
  analogWrite(9, reading / 4);
  Serial.println(reading);
}

Check your understanding

What PWM value does an input of 512 produce here?