from machine import Pin,PWM
import utime

MID = 500000
MIN = 1500000
MAX = 2400000

led = Pin(25,Pin.OUT)
pwm = PWM(Pin(15))

pwm.freq(50)

while True:
    pwm.duty_ns(MID)
    utime.sleep(1)

    pwm.duty_ns(MIN)
    utime.sleep(1)
  
    pwm.duty_ns(MAX)
    utime.sleep(1)