from machine import *
from time import *

LDR= ADC(Pin(27))
LDR_threshold= 20000
trig= Pin(11,Pin.OUT)
echo= Pin(13,Pin.IN)
LED= Pin(15,Pin.OUT)
buzzer= PWM(Pin(20))
buzzer.freq(1000)

while True:
    Light_value= LDR.read_u16()
    print('LDR:', Light_value)

    if Light_value < LDR_threshold:
        print('Day mode OFF')
        LED.value(0)
        buzzer.duty_u16(0)
        sleep(0.25)
        continue

    else:
        print('Night mode ON')
        trig.value(0)
        sleep_us(2)
        trig.value(1)
        sleep_us(10)
        trig.value(0)

    duration= time_pulse_us(echo,1)
    distance= (duration*0.0343)/2

    print('distance=', distance, 'cm')

    if distance > 80:
        LED.value(0)
        buzzer.duty_u16(0)

    elif distance > 30 and distance <= 80:
        LED.value(1)
        print("welcome light")
        buzzer.duty_u16(0)

    elif distance <= 30:
        LED.value(1)
        buzzer.duty_u16(20000)
        print("security alert")

     sleep(0.8)

 continue