from machine import *
from time import *

led = Pin(21, Pin.OUT)
LDR = ADC(Pin(28))

sensor_voltage = 3.3
trig = Pin(18, Pin.OUT)
echo = Pin(20, Pin.IN)
buzzer = PWM(Pin(15))
buzzer.freq(100)

led.value(0)
buzzer.duty_u16(0)

while True:
     light = LDR.read_u16(28)
     V = (light/65535)*sensor_voltage
print("Voltage is", V) 

if V >= 2.0:
  led.value(0)
  buzzer.duty_u16(0) 
print("Day time - System OFF")
trig.value(1)
  sleep_us(10)
  trig.value(0)

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

if distance > 100:
  led.value(0)
  buzzer.duty_u16(0)
  print("No one near")

elif distance < 50 and distance <= 100:
  led.value(0)
  buzzer.duty_u16(0)
  print("Welcome light")

else distance <= 50:
  led.value(1)
  buzzer.duty_u16(20000)
  print("Security Alert!")

  sleep(0.5)