====== Alertor ======

**//The Circuit://**
{{:hpc0:doorbell.jpg?nolink|}}

**//The Code://**

<code py>
  1 #!/usr/bin/env python3                                                                                      
  2 ########################################################################
  3 # Filename    : Alertor.py
  4 # Description : Make Alertor with buzzer and button
  5 # Author      : www.freenove.com
  6 # modification: 2019/12/27
  7 ########################################################################
  8 import RPi.GPIO as GPIO
  9 import time
 10 import math
 11          
 12 buzzerPin = 11    # define the buzzerPin
 13 buttonPin = 12    # define the buttonPin
 14          
 15 #Initial setup of the board and buzzer
 16 def setup():
 17     global p
 18     GPIO.setmode(GPIO.BOARD)                                 # Use PHYSICAL GPIO Numbering
 19     GPIO.setup(buzzerPin, GPIO.OUT)                          # set RGBLED pins to OUTPUT mode
 20     GPIO.setup(buttonPin, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Set buttonPin to INPUT mode. Set up to HIGH
 21     p = GPIO.PWM(buzzerPin, 1)
 22     p.start(0);
 23          
 24          
 25 #function that will activate the alertor when button is pressed
 26 def loop():
 27     while True:
 28         if GPIO.input(buttonPin)==GPIO.LOW:
 29             alertor()
 30             print ('alertor turned on >>> ')
 31         else :
 32             stopAlertor()
 33             print ('alertor turned off <<<')
 34          
 35 #function that sets the frequency of sound made
 36 def alertor():
 37     p.start(50)
 38     for x in range(0,361):                       # Make frequency of the alertor that of a sine wave 
 39         sinVal = math.sin(x * (math.pi / 180.0)) # calculate the sine value
 40         toneVal = 2000 + sinVal * 500            # Add to the frequency so that humans can hear it
 41         p.ChangeFrequency(toneVal)               # Change to the new Frequency 
 42         time.sleep(0.001)
 43          
 44 #function that stops the alertor
 45 def stopAlertor():
 46     p.stop()
 47          
 48 #function that clears the board
 49 def destroy():
 50     GPIO.output(buzzerPin, GPIO.LOW)             # Turn off buzzer
 51     GPIO.cleanup()                               # Release GPIO resource
 52          
 53 if __name__ == '__main__':
 54     print ('Program is starting...')
 55     setup()
 56     try: 
 57         loop()
 58     except KeyboardInterrupt:  # When program ends clean up
 59         destroy()
</code>

This project has the same setup as the [[hpc0:doorbell|doorbell]] project, with the only change being that instead of an active buzzer we replaced it with a passive buzzer. After replacing the buzzer and activating the code we find that buzzer makes a new sound that changes frequency. This change in frequency is using number along a sine wave, which is then converted into a frequency that we can hear. As for the code I added comments to describe the functions, made a couple of the longer comments more readable, and made the comments align with each other.