⚙️ PWM (Pulse Width Modulation) is one of the most commonly used techniques in electronics for controlling motors, LEDs, and more.
If you’re building circuits or working with microcontrollers like Arduino, STM32, or Raspberry Pi, understanding how to calculate PWM frequency is essential.
In this guide, we’ll explain what PWM frequency is, how to calculate it, and how it affects your projects.
Table of Contents
🙋♀️ What Is PWM Frequency?
PWM frequency is the number of times a PWM signal completes one full ON/OFF cycle in one second. It’s measured in Hertz (Hz).
In PWM, the signal alternates between high (ON) and low (OFF). The frequency determines how fast this switching happens, while the duty cycle determines how long the signal stays high in each cycle.
For example:
- A PWM frequency of 1,000 Hz means the signal switches on and off 1,000 times per second.
- A duty cycle of 50% means it is ON half the time and OFF half the time.
⚙️ PWM Frequency Calculator
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🧮 Formula for Calculating PWM Frequency
To calculate PWM frequency, you typically use this formula when working with a microcontroller timer:
PWM Frequency = Clock Speed / (Prescaler × Timer Resolution)Where:
- Clock Speed = system clock of your microcontroller (e.g., 16 MHz)
- Prescaler = a divisor that slows down the clock
- Timer Resolution = the number of steps in the timer (e.g., 256 for 8-bit, 65536 for 16-bit)
📌 Example
Let’s say you’re using a microcontroller with:
- Clock Speed = 16,000,000 Hz (16 MHz)
- Prescaler = 64
- Timer Resolution = 256 (for 8-bit PWM)
PWM Frequency = 16,000,000 / (64 × 256) = 976.56 HzSo your PWM signal will operate at around 977 Hz.
🔧 Common PWM Frequency Values
| Application | Recommended Frequency |
|---|---|
| LEDs | 500 – 1,000 Hz |
| DC Motors | 1,000 – 20,000 Hz |
| Audio Applications | > 20,000 Hz |
| Servo Motors | 50 Hz |
🔍 Choosing the Right Frequency
- Low frequencies can cause flickering in LEDs or noisy motors.
- High frequencies reduce visible flicker and can improve motor smoothness but may cause more switching losses.
🧰 Tools to Help
Many microcontrollers come with built-in PWM libraries that let you specify frequency and duty cycle directly. Use our online calculators or manufacturer’s IDE tools to simplify setup.