Why PWM is needed for analog-like control in Raspberry Pi - Quick Recap

Recall & Review

beginner

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

PWM stands for Pulse Width Modulation. It controls the amount of power delivered to a device by switching it on and off very quickly, changing the width of the 'on' pulses.

beginner

Why can't Raspberry Pi output true analog voltage directly?

Raspberry Pi GPIO pins can only output digital signals: either ON (3.3V) or OFF (0V). They cannot produce a smooth range of voltages like an analog signal.

beginner

How does PWM create an analog-like effect using digital signals?

By changing the ratio of ON time to OFF time (duty cycle), PWM makes devices behave as if they receive different voltage levels, even though the signal is digital.

beginner

Give a real-life example of PWM controlling brightness.

A lamp connected to a PWM signal will appear dimmer or brighter depending on how long the signal stays ON versus OFF in each cycle, similar to turning a dimmer switch.

beginner

What is the advantage of using PWM over a simple ON/OFF switch for controlling devices?

PWM allows smooth control of power, making devices like motors or LEDs run at different speeds or brightness levels instead of just fully ON or OFF.

What does PWM control to simulate analog output?

A The ratio of ON to OFF time in a digital signal

B The voltage level of the GPIO pin

C The frequency of the Raspberry Pi CPU

D The temperature of the device

PWM changes the duty cycle, which is the ratio of ON time to OFF time, to simulate different power levels.

Why can't Raspberry Pi GPIO pins output true analog voltage?

A They only work with sensors

B They are too slow

C They have low current

D They only output digital signals (ON or OFF)

GPIO pins can only be ON (3.3V) or OFF (0V), so they cannot produce a smooth range of voltages.

What happens if the PWM duty cycle is 100%?

A The device is fully ON

B The device is fully OFF

C The device blinks slowly

D The device runs at half power

A 100% duty cycle means the signal is ON all the time, so the device receives full power.

How does PWM help control the brightness of an LED?

A By changing the LED temperature

B By changing how long the LED is ON in each cycle

C By changing the LED size

D By changing the LED color

PWM adjusts the ON time in each cycle, making the LED appear dimmer or brighter.

Which of these is NOT a benefit of PWM?

A Smooth control of power

B Reduced heat generation

C Direct analog voltage output

D Energy efficiency

PWM does not output true analog voltage; it simulates it by switching digital signals.

Explain why PWM is used on Raspberry Pi to control devices like motors or LEDs instead of just turning them ON or OFF.

Think about how PWM changes the time the signal is ON versus OFF.

Describe how changing the duty cycle in PWM affects the behavior of a connected device.

Consider what happens when the ON time is longer or shorter.