Arduino PWM Frequency Calculator

Calculated Frequency: 490.20 Hz
Time Period: 2.04 ms

What is the Arduino PWM Frequency Calculator?

Pulse Width Modulation (PWM) is a vital technique used in Arduino microcontrollers to simulate analog signals using digital outputs. By toggling a digital pin on and off at very high speeds, you can control the power delivered to devices like LEDs, DC motors, and servos. This calculator allows engineers and hobbyists to determine the exact output frequency and time period based on the internal clock speed, hardware prescalers, and specific timer resolutions.

How to Calculate Arduino PWM Frequency

The frequency of a PWM signal on an Arduino (like the Uno, Nano, or Mega) is determined by the system clock (usually 16MHz), the prescaler value assigned to the hardware timer, and the PWM mode being used. There are two primary modes:

  • Fast PWM: The timer counts from 0 to the maximum resolution (TOP) and resets. The formula is: Freq = Clock / (Prescaler * 2^Resolution).
  • Phase Correct PWM: The timer counts up to TOP and then back down to 0, resulting in a more symmetrical wave but halving the frequency. The formula is: Freq = Clock / (Prescaler * 2 * 2^Resolution).

Frequently Asked Questions

Why is the default frequency 490Hz or 980Hz?

On standard Arduino boards like the Uno, pins 3, 9, 10, and 11 run at approximately 490Hz, while pins 5 and 6 run at roughly 980Hz. This is because pins 5 and 6 are tied to Timer 0, which is also used for the millis() and delay() functions, requiring a different configuration.

Does changing PWM frequency affect other functions?

Yes. If you modify the prescaler for Timer 0, time-related functions like delay() and millis() will track time incorrectly. It is generally recommended to use Timer 1 or Timer 2 for custom PWM frequencies to avoid breaking core Arduino functionality.

What is a Prescaler?

A prescaler is a hardware component that divides the system clock frequency by a fixed factor (like 8, 64, or 1024). This allows the timer to run slower than the CPU, enabling the generation of lower-frequency signals without requiring manual CPU intervention.