The Official Raspberry Pi Projects Book - Projects_Book_v4

Tutorial

raspberrypi.org/magpi The Official Raspberry Pi Projects Book 109

DIY SUNRISE ALARM

directory containing the code by using the command

cd rpesk-advanced.

>STEP-05

Run the code

The time has come to run the code and test out the

alarm! After checking that the circuit you have built

is an exact replica of the one shown in the circuit

diagram, and that it is connected to the Pi, run the

command sudo python 01_sunrise_alarm.py. You

can test that the alarm works by shining a torch at the

photoresistor from within a fairly light room. The LEDs

should start to flash, and the buzzer should sound. If

this happens, congratulations!

from Tkinter import *

import RPi.GPIO as GPIO

import time, math

GPIO.cleanup()

GPIO.setmode(GPIO.BCM)

sunrise = 50

a_pin = 18

b_pin = 23

buzzer_pin = 24

red_pin1 = 27

red_pin2 = 22

GPIO.setup(buzzer_pin, GPIO.OUT)

GPIO.setup(red_pin1, GPIO.OUT)

GPIO.setup(red_pin2, GPIO.OUT)

def discharge():

GPIO.setup(a_pin, GPIO.IN)

GPIO.setup(b_pin, GPIO.OUT)

GPIO.output(b_pin, False)

time.sleep(0.01)

def charge_time():

GPIO.setup(b_pin, GPIO.IN)

GPIO.setup(a_pin, GPIO.OUT)

GPIO.output(a_pin, True)

t1 = time.time()

while not GPIO.input(b_pin):

pass

t2 = time.time()

return (t2 - t1) * 1000000

def analog_read():

discharge()

return charge_time()

Sunrise_alarm.py

Language

>PYTHON 2

DOWNLOAD:

magpi.cc/2eCbCtZ

>STEP-06

Make it your own

The default threshold for the alarm’s activation is

when the photoresistor reaches a value of 50, which

works well for testing as described previously.

However, in order to use the alarm to accurately

detect the sunrise in the morning, this value can

be changed by entering the file editor with the

command nano 01_sunrise_alarm.py and then

changing the value found on line 13. We would

recommend that you use 30 for fairly accurate

detection of dawn. Save this change by pressing

CTRL+X, followed by Y, then the ENTER key. This

code can now be run again as in Step 05.

def read_resistance():

n = 20

total = 0 ;

for i in range( 1 , n):

total = total + analog_read()

reading = total / float(n)

resistance = reading * 6.05 - 939

return resistance

def light_from_r(R):

return math.log(1000000.0/R) * 10.0

while True:

GPIO.output(red_pin1, False)

GPIO.output(red_pin2, False)

light = light_from_r(read_resistance())

print light

x = 0

if light > sunrise:

GPIO.output(red_pin1, True)

GPIO.output(red_pin2, False)

while True:

x = x + 1

GPIO.output(buzzer_pin, True)

time.sleep(0.001)

GPIO.output(buzzer_pin, False)

time.sleep(0.001)

if x == 250 :

x = 0

break

GPIO.output(red_pin1, False)

GPIO.output(red_pin2, True)

while True:

x = x + 1

GPIO.output(buzzer_pin, True)

time.sleep(0.001)

GPIO.output(buzzer_pin, False)

time.sleep(0.001)

if x == 250 :

x = 0

break