import RPi.GPIO as GPIO
import time
led_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_pin, GPIO.OUT)
pwm_led = GPIO.PWM(led_pin, 500)
pwm_led.start(100)
# Brightness has to have a value between 0 and 100
# starts with 0
duty_s = 0
duty = int(duty_s)
while duty < 100:
pwm_led.ChangeDutyCycle(duty)
duty+=20
time.sleep(1.5)