Enter your Clock Frequency, Prescaler Value, Timer Resolution, Desired PWM Frequency, Duty Cycle, and Pulse Width into the PWM Calculator to find your Actual PWM Frequency, along with the TOP Register Value, Duty Cycle Resolution, Frequency Error, and Calculated Pulse Width.
Actual PWM Frequency
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TOP Register Value
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Duty Cycle Resolution
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Frequency Error
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Calculated Pulse Width
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Period
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For DC motor control, frequencies between 1kHz-20kHz work well. Higher frequencies (15-20kHz) reduce audible noise but increase switching losses. For servo motors, use 50Hz with 1-2ms pulse widths.
Higher prescaler values reduce the effective clock frequency, allowing lower PWM frequencies but reducing resolution. Lower prescalers provide better resolution but limit the minimum achievable frequency.
PWM frequencies are constrained by integer register values. The calculator shows the closest achievable frequency and the error percentage. Choose different prescaler values to minimize error.
16-bit timers provide much better frequency resolution and can achieve lower frequencies. Use 8-bit timers only when you need very high PWM frequencies or have limited hardware resources.
Duty cycle is the percentage of time the PWM signal is HIGH. For motor control, it determines speed. 50% duty cycle means equal time HIGH and LOW, while 25% means the signal is HIGH for 1/4 of each cycle.
PWM frequency accuracy depends on the crystal oscillator tolerance (typically ±20ppm) and register resolution. The calculator shows theoretical values - actual frequencies may vary slightly due to hardware tolerances.