PWM frequency and duty cycle relationship in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does PWM stand for and what is its basic purpose?

PWM stands for Pulse Width Modulation. It is used to control the amount of power delivered to a device by switching it on and off very quickly.

beginner

What is PWM frequency?

PWM frequency is how many times per second the PWM signal completes one on-off cycle. It is measured in Hertz (Hz).

beginner

What is PWM duty cycle?

PWM duty cycle is the percentage of time the signal is ON during one cycle. For example, 50% means the signal is ON half the time and OFF half the time.

intermediate

How does changing the PWM frequency affect the output device?

Changing the PWM frequency changes how fast the signal switches ON and OFF. Too low frequency can cause flickering or noise, too high might not be supported by the device.

intermediate

How do frequency and duty cycle work together in PWM?

Frequency sets how fast the signal cycles ON and OFF. Duty cycle controls how long the signal stays ON in each cycle. Together, they control the power and behavior of the device.

What does a 25% duty cycle mean in PWM?

A Signal is ON 75% of the time and OFF 25% of the time

B Signal is ON 25% of the time and OFF 75% of the time

C Signal frequency is 25 Hz

D Signal frequency is 75 Hz

Duty cycle is the percentage of time the signal is ON during one cycle.

If you increase the PWM frequency, what happens?

A The signal stays ON longer

B The signal switches ON and OFF slower

C The duty cycle increases automatically

D The signal switches ON and OFF faster

Frequency controls how many times the signal cycles ON and OFF per second.

Which of these affects how bright an LED controlled by PWM will be?

A Duty cycle

B Frequency only

C Neither frequency nor duty cycle

D The color of the LED

Duty cycle controls how long the LED is ON, affecting brightness.

What unit is PWM frequency measured in?

A Hertz (Hz)

B Volts (V)

C Amps (A)

D Seconds (s)

Frequency is measured in Hertz, meaning cycles per second.

If PWM frequency is too low, what might happen to a motor controlled by PWM?

A It will stop completely

B It will run faster

C It may vibrate or make noise

D It will overheat immediately

Low frequency can cause the motor to vibrate or produce noise due to slow switching.

Explain in your own words how PWM frequency and duty cycle work together to control a device.

Think about how fast the signal switches and how long it stays ON.

Describe what happens if you keep the duty cycle constant but increase the PWM frequency.

Focus on the effect of frequency change alone.