Arduino Basics — Pwm Pulse Width Modulation — 30 Days Lost in Space Help Center

Simulate analog output using digital pins. Control LED brightness, motor speed, and servo positions with analogWrite().

What is PWM?

PWM (Pulse Width Modulation) rapidly switches a pin between HIGH and LOW to simulate voltages between 0V and 5V. The ratio of ON time to total time is the duty cycle.

Duty Cycle

0%:   |___________________________|  = 0V
25%:  |██████_____________________| = 1.25V
50%:  |█████████████______________|  = 2.5V
75%:  |██████████████████_________| = 3.75V
100%: |████████████████████████████| = 5V

analogWrite()

analogWrite(pin, value);
// value: 0 (always off) to 255 (always on)

Note: Despite the name, analogWrite() is digital. It produces a square wave, not a true analog voltage.

PWM Pins

Only pins marked with ~ support PWM:

| HERO Board | PWM Pins | |------------|----------| | Available | 3, 5, 6, 9, 10, 11 |

Applications

| Application | Value Range | |-------------|------------| | LED brightness | 0-255 | | Motor speed | 0-255 | | Servo position | (use Servo library) | | Speaker tone | (use tone() instead) |

PWM Frequency

Arduino PWM runs at:

490 Hz on pins 3, 9, 10, 11
980 Hz on pins 5, 6