PWMLED for brightness in Raspberry Pi - Step-by-Step Execution

Concept Flow - PWMLED for brightness

Start

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Set PWMLED pin

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Set brightness value (0.0 to 1.0)

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PWM signal adjusts LED brightness

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LED glows with set brightness

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End or change brightness

This flow shows how setting a brightness value changes the LED brightness using PWM signals.

Execution Sample

Raspberry Pi

from gpiozero import PWMLED
led = PWMLED(17)
led.value = 0.5  # half brightness

This code sets up a PWM LED on pin 17 and sets its brightness to half.

Execution Table

Step	Action	PWMLED.value	LED Brightness Level	Notes
1	Create PWMLED on pin 17	0.0	Off	LED starts off by default
2	Set led.value = 0.5	0.5	Medium brightness	LED glows at half brightness
3	Set led.value = 1.0	1.0	Full brightness	LED glows fully bright
4	Set led.value = 0.0	0.0	Off	LED turns off
5	Set led.value = 0.75	0.75	Bright	LED glows bright but not full
6	End	0.75	Bright	Program ends, LED stays at last brightness

💡 Program ends after setting brightness; LED stays at last set brightness.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
led.value	0.0	0.5	1.0	0.0	0.75	0.75
LED Brightness	Off	Medium	Full	Off	Bright	Bright

Key Moments - 3 Insights

Why does led.value accept numbers between 0.0 and 1.0?

Because led.value controls the brightness as a fraction of full power, where 0.0 means off and 1.0 means fully on, as shown in steps 2 to 5 in the execution_table.

What happens if you set led.value to a number greater than 1 or less than 0?

The PWMLED class expects values only between 0.0 and 1.0; values outside this range may cause errors or unexpected behavior, so always keep values within this range as shown in the execution_table.

Does the LED turn off immediately when led.value is set to 0?

Yes, setting led.value to 0 turns the LED off immediately, as seen in step 4 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what is the LED brightness level after step 3?

A Off

B Medium brightness

C Full brightness

D Bright but not full

💡 Hint

Check the 'LED Brightness Level' column at step 3 in the execution_table.

At which step does the LED turn off?

A Step 4

B Step 2

C Step 5

D Step 3

💡 Hint

Look for 'Off' in the 'LED Brightness Level' column in the execution_table.

If led.value is set to 0.25 instead of 0.5 at step 2, how would the LED brightness change?

A LED brightness would be full

B LED brightness would be dimmer than medium

C LED brightness would be off

D LED brightness would be brighter than full

💡 Hint

Compare the brightness levels for different led.value settings in the variable_tracker.

Concept Snapshot

PWMLED controls LED brightness by setting led.value between 0.0 (off) and 1.0 (full brightness).
Changing led.value adjusts the pulse width modulation signal to vary brightness smoothly.
Use led.value = x where x is a float from 0.0 to 1.0.
Setting led.value to 0 turns LED off immediately.
Values outside 0.0-1.0 are invalid and should be avoided.

Full Transcript

This lesson shows how to control LED brightness on a Raspberry Pi using PWMLED from gpiozero. We start by creating a PWMLED object on a pin, then set its value between 0.0 and 1.0 to adjust brightness. The execution table traces steps where brightness changes from off to medium, full, off again, and bright. The variable tracker shows how led.value and LED brightness change step by step. Key moments clarify why values must be between 0.0 and 1.0 and what happens when setting led.value to 0. The quiz tests understanding of brightness levels at different steps and effects of changing led.value. The snapshot summarizes the main points for quick reference.