LED Fade Effect Using Built-in LED (PWM)
Hardware Required
- PICUNO Microcontroller board (built-in LED on GPIO 14)
- USB cable (for power and programming)
Description
The PWM is used to control the brightness of the built-in LED. By gradually increasing the duty cycle from 0 to 255 and then decreasing it back to 0, the LED appears to smoothly fade in and out. This is done continuously in a loop.
Circuit Diagram
Circuit
- Connect the PICUNO board to the computer using a USB cable.
- No external wires or breadboard are required.
- The built-in LED is internally connected to GPIO 14, which supports PWM.
- The PWM signal is used to vary the brightness of the LED by changing the duty cycle.
Schematic
This project uses the built-in LED on GPIO 14 of the PicUNO board. No additional circuit components are required.
Code - C
int ledPin = 14; // Built-in LED pin (PWM capable)
void setup() {
pinMode(ledPin, OUTPUT);
}
void loop() {
// Fade in
for (int brightness = 0; brightness <= 255; brightness += 5) {
analogWrite(ledPin, brightness); // Set LED brightness
delay(30); // Wait for a short time
}
// Fade out
for (int brightness = 255; brightness >= 0; brightness -= 5) {
analogWrite(ledPin, brightness); // Set LED brightness
delay(30); // Wait for a short time
}
}
void setup() {
pinMode(ledPin, OUTPUT);
}
void loop() {
// Fade in
for (int brightness = 0; brightness <= 255; brightness += 5) {
analogWrite(ledPin, brightness); // Set LED brightness
delay(30); // Wait for a short time
}
// Fade out
for (int brightness = 255; brightness >= 0; brightness -= 5) {
analogWrite(ledPin, brightness); // Set LED brightness
delay(30); // Wait for a short time
}
}
int ledPin = 14 - Assigns GPIO 14 to control the LED.
pinMode(ledPin, OUTPUT) - Configures the pin as an output.
analogWrite(ledPin, brightness) - Sets PWM output with a value from 0 to 255.
delay(30) - Adds a small pause to make the fade effect smooth.
pinMode(ledPin, OUTPUT) - Configures the pin as an output.
analogWrite(ledPin, brightness) - Sets PWM output with a value from 0 to 255.
delay(30) - Adds a small pause to make the fade effect smooth.
Code - Micropython
from machine import Pin, PWM
import time
led = PWM(Pin(14)) # PWM on pin 14 (onboard LED)
led.freq(1000) # Set PWM frequency to 1kHz
while True:
# Fade in
for duty in range(0, 65536, 2048): # step = 2048
led.duty_u16(duty)
time.sleep(0.05)
# Fade out
for duty in range(65535, -1, -2048):
led.duty_u16(duty)
time.sleep(0.05)
import time
led = PWM(Pin(14)) # PWM on pin 14 (onboard LED)
led.freq(1000) # Set PWM frequency to 1kHz
while True:
# Fade in
for duty in range(0, 65536, 2048): # step = 2048
led.duty_u16(duty)
time.sleep(0.05)
# Fade out
for duty in range(65535, -1, -2048):
led.duty_u16(duty)
time.sleep(0.05)
PWM(Pin(14)) - Sets GPIO 14 to work as a PWM output.
led.freq(1000) - Sets the PWM frequency to 1kHz.
led.duty_u16(duty) - Sets the PWM duty cycle from 0 to 65535.
time.sleep(0.05) - Adds a small pause for smooth fading transitions.
led.freq(1000) - Sets the PWM frequency to 1kHz.
led.duty_u16(duty) - Sets the PWM duty cycle from 0 to 65535.
time.sleep(0.05) - Adds a small pause for smooth fading transitions.