Logical Thinking: March 2017

Problem we are solving here is.

1. User raspberry pi to get the room temperature
2. Store the temp in a sqlite database.
3. Display the results in a neat graph using a webpage.

Hardware required for this project:
DS18B20 Temperature Sensor
Raspberry Pi
4.7 ohm resistor
Soldering rod
Three wires with female connectors on each end

First of all get your pi ready for the work

-- Install SQLite database

sudo apt-get install sqlite3

-- create a database in the home directory of pi user

sqlite3 mydatabase.db

-- Create table to store the temperature readings

BEGIN;

CREATE TABLE temps (temptime DATETIME, temp NUMERIC);

COMMIT;

-- A tip to get some help

sqlite> .help

-- To exit out of sqlite command prompt

sqlite> .exit

-- create get temp.py to get the temperature

#!/usr/bin/env python

import sqlite3

import os

import time

import glob

# global variables

speriod=(15*60)-1

dbname='/home/pi/tempdb/mydatabase.db'

# store the temperature in the database

def log_temperature(temp):

conn=sqlite3.connect(dbname)

curs=conn.cursor()

# bavita added , 'localtime' to get the local time from machine else it is showing GMT

curs.execute("INSERT INTO temps values(datetime('now', 'localtime'), (?))", (temp,))

# commit the changes

conn.commit()

conn.close()

# get temerature

# returns None on error, or the temperature as a float

def get_temp(devicefile):

try:

fileobj = open(devicefile,'r')

lines = fileobj.readlines()

fileobj.close()

except:

return None

# get the status from the end of line 1

status = lines[0][-4:-1]

# is the status is ok, get the temperature from line 2

if status=="YES":

print status

tempstr= lines[1][-6:-1]

tempvalue=float(tempstr)/1000

print tempvalue

return tempvalue

else:

print "There was an error."

return None

# main function

# This is where the program starts

def main():

# enable kernel modules

os.system('sudo modprobe w1-gpio')

os.system('sudo modprobe w1-therm')

# search for a device file that starts with 28

devicelist = glob.glob('/sys/bus/w1/devices/28*')

if devicelist=='':

return None

else:

# append /w1slave to the device file

w1devicefile = devicelist[0] + '/w1_slave'

# while True:

# get the temperature from the device file

temperature = get_temp(w1devicefile)

if temperature != None:

print "temperature="+str(temperature)

else:

# Sometimes reads fail on the first attempt

# so we need to retry

temperature = get_temp(w1devicefile)

print "temperature="+str(temperature)

# Store the temperature in the database

log_temperature(temperature)

if __name__=="__main__":

main()

-- test apache
open the bowser from a machine other than the pi and type the ip address of pi like below and hit enter

http://192.168.0.2/

The page should display something like below:

-- Solder sensor and resistor as described below and then use the wire to connect them to GPIO.

-- The final product should looks something like below:

-- After the setup perform a quick test on sensor and see if it works and that is done as below:

Here temp is 16687 / 1000 = 16.687 C

Please note that if the black sensor is getting too hot then you have soldered it other way around, change the pins and it should be fine.

-- Enable cgi-bin on apache

We will be writing the code in python and in order for that code to display content on webpage we need to change apache config to enable cgi scripts.

Go to /usr/lib/cgi-bin and create sensor.py with chmod 777

Now go to /etc/apache2/sites-available

edit file called default and add below in red color

AddHandler cgi-script .py

AllowOverride None

Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch

Order allow,deny

Allow from all

</Directory>

Note the bit in blue /usr/lib/cgi-bin this is where your web application sensor.py should go and work in browser.

-- code for sensor.py

#!/usr/bin/env python

import sqlite3

import sys

import cgi

import cgitb

# global variables

speriod=(15*60)-1

#dbname='/var/www/mydatabase.db'

dbname='/home/pi/tempdb/mydatabase.db'

# print the HTTP header

def printHTTPheader():

print "Content-type: text/html\n\n"

# print the HTML head section

# arguments are the page title and the table for the chart

def printHTMLHead(title, table):

print "<head>"

print " <title>"

print title

print " </title>"

print_graph_script(table)

print "</head>"

# get data from the database

# if an interval is passed,

# return a list of records from the database

def get_data(interval):

conn=sqlite3.connect(dbname)

curs=conn.cursor()

if interval == None:

curs.execute("SELECT * FROM temps")

else:

curs.execute("SELECT * FROM temps WHERE temptime>datetime('now','localtime','-%s hours')" % interval)

# curs.execute("SELECT * FROM temps WHERE temptime>datetime('2013-09-19 21:30:02','-%s hours') AND temptime<=datetime('2013-09-19 21:31:02')" % interval)

rows=curs.fetchall()

conn.close()

return rows

# convert rows from database into a javascript table

def create_table(rows):

chart_table=""

for row in rows[:-1]:

rowstr="['{0}', {1}],\n".format(str(row[0]),str(row[1]))

chart_table+=rowstr

row=rows[-1]

rowstr="['{0}', {1}]\n".format(str(row[0]),str(row[1]))

chart_table+=rowstr

return chart_table

# print the javascript to generate the chart

# pass the table generated from the database info

def print_graph_script(table):

# google chart snippet

chart_code="""

google.load("visualization", "1", {packages:["corechart"]});

google.setOnLoadCallback(drawChart);

function drawChart() {

var data = google.visualization.arrayToDataTable([ ['Time', 'Temperature'],%s ]);

var options = {

hAxis: {

title: 'Time'

vAxis: {

title: 'Temperature'

title: 'Temperature Vs Time',

backgroundColor: '#f1f8e9'

};

var chart = new google.visualization.LineChart(document.getElementById('chart_div'));

chart.draw(data, options);

}

</script>"""

print chart_code % (table)

# print the div that contains the graph

def show_graph():

print "<h2>Temperature Chart</h2>"

# Bavita commented below to make the graph bigger

# print '<div id="chart_div" style="width: 900px; height: 500px;"></div>'

print '<div id="chart_div" style="width: 1300px; height: 700px;"></div>'

# connect to the db and show some stats

# argument option is the number of hours

def show_stats(option):

conn=sqlite3.connect(dbname)

curs=conn.cursor()

if option is None:

option = str(24)

curs.execute("SELECT temptime,max(temp) FROM temps WHERE temptime>datetime('now','localtime','-%s hour') AND temptime<=datetime('now','localtime')" % option)

# curs.execute("SELECT temptime,max(temp) FROM temps WHERE temptime>datetime('2013-09-19 21:30:02','-%s hour') AND temptime<=datetime('2013-09-19 21:31:02')" % option)

rowmax=curs.fetchone()

rowstrmax="{0}&nbsp&nbsp&nbsp{1}C".format(str(rowmax[0]),str(rowmax[1]))

curs.execute("SELECT temptime,min(temp) FROM temps WHERE temptime>datetime('now','localtime','-%s hour') AND temptime<=datetime('now','localtime')" % option)

# curs.execute("SELECT temptime,min(temp) FROM temps WHERE temptime>datetime('2013-09-19 21:30:02','-%s hour') AND temptime<=datetime('2013-09-19 21:31:02')" % option)

rowmin=curs.fetchone()

rowstrmin="{0}&nbsp&nbsp&nbsp{1}C".format(str(rowmin[0]),str(rowmin[1]))

curs.execute("SELECT avg(temp) FROM temps WHERE temptime>datetime('now','localtime','-%s hour') AND temptime<=datetime('now','localtime')" % option)

# curs.execute("SELECT avg(temp) FROM temps WHERE temptime>datetime('2013-09-19 21:30:02','-%s hour') AND temptime<=datetime('2013-09-19 21:31:02')" % option)

rowavg=curs.fetchone()

curs.execute("select * from temps where temptime =(select max(temptime) FROM temps WHERE temptime>datetime('now','localtime','-1 hour') AND temptime<=datetime('now','localtime'))")

rowcurrent=curs.fetchone()

rowstrcurrent="{0}&nbsp&nbsp&nbsp{1}C".format(str(rowcurrent[0]),str(rowcurrent[1]))

print "<hr>"

print "<h2>Current temperature&nbsp</h2>"

print rowstrcurrent

print "<h2>Minumum temperature&nbsp</h2>"

print rowstrmin

print "<h2>Maximum temperature</h2>"

print rowstrmax

print "<h2>Average temperature</h2>"

print "%.3f" % rowavg+"C"

print "<hr>"

print "<h2>In the last hour:</h2>"

print "<table>"

print "<tr><td><strong>Date/Time</strong></td><td><strong>Temperature</strong></td></tr>"

#rows=curs.execute("SELECT * FROM temps WHERE temptime>datetime('now','-1 hour') AND temptime<=datetime('now')")

# display the temp in last hour under "In the last hour"

rows=curs.execute("SELECT * FROM temps WHERE temptime>datetime('now','localtime','-1 hour') AND temptime<=datetime('now','localtime')")

# rows=curs.execute("SELECT * FROM temps WHERE temptime>datetime('2013-09-19 21:30:02','-1 hour') AND temptime<=datetime('2013-09-19 21:31:02')")

for row in rows:

rowstr="<tr><td>{0}&emsp;&emsp;</td><td>{1}C</td></tr>".format(str(row[0]),str(row[1]))

print rowstr

print "</table>"

print "<hr>"

conn.close()

def print_time_selector(option):

print """<form action="/cgi-bin/webgui.py" method="POST">

Show the temperature logs for

<select name="timeinterval">"""

if option is not None:

if option == "1":

print "<option value=\"1\" selected=\"selected\">the last 1 hours</option>"

else:

print "<option value=\"1\">the last 1 hours</option>"

if option == "2":

print "<option value=\"2\" selected=\"selected\">the last 2 hours</option>"

else:

print "<option value=\"2\">the last 2 hours</option>"

if option == "3":

print "<option value=\"3\" selected=\"selected\">the last 3 hours</option>"

else:

print "<option value=\"3\">the last 3 hours</option>"

if option == "6":

print "<option value=\"6\" selected=\"selected\">the last 6 hours</option>"

else:

print "<option value=\"6\">the last 6 hours</option>"

if option == "12":

print "<option value=\"12\" selected=\"selected\">the last 12 hours</option>"

else:

print "<option value=\"12\">the last 12 hours</option>"

if option == "24":

print "<option value=\"24\" selected=\"selected\">the last 24 hours</option>"

else:

print "<option value=\"24\">the last 24 hours</option>"

if option == "48":

print "<option value=\"48\" selected=\"selected\">the last 2 Days</option>"

else:

print "<option value=\"48\">the last 2 days</option>"

if option == "168":

print "<option value=\"168\" selected=\"selected\">the last 7 Days</option>"

else:

print "<option value=\"168\">the last 7 days</option>"

if option == "336":

print "<option value=\"336\" selected=\"selected\">the last 14 Days</option>"

else:

print "<option value=\"336\">the last 14 days</option>"

if option == "720":

print "<option value=\"720\" selected=\"selected\">the last 30 Days</option>"

else:

print "<option value=\"720\">the last 30 days</option>"

if option == "4320":

print "<option value=\"4320\" selected=\"selected\">the last 180 Days</option>"

else:

print "<option value=\"4320\">the last 180 days</option>"

else:

print """

<option value="1">the last 1 hours</option>

<option value="2">the last 2 hours</option>

<option value="3">the last 3 hours</option>

<option value="6">the last 6 hours</option>

<option value="12">the last 12 hours</option>

<option value="24" selected="selected">the last 24 hours</option>

"""

print """ </select>

</form>"""

# check that the option is valid

# and not an SQL injection

def validate_input(option_str):

# check that the option string represents a number

if option_str.isalnum():

# check that the option is within a specific range

if int(option_str) > 0 and int(option_str) <= 4320:

return option_str

else:

return None

else:

return None

#return the option passed to the script

def get_option():

form=cgi.FieldStorage()

if "timeinterval" in form:

option = form["timeinterval"].value

return validate_input (option)

else:

return None

# main function

# This is where the program starts

def main():

cgitb.enable()

# get options that may have been passed to this script

option=get_option()

if option is None:

option = str(24)

# get data from the database

records=get_data(option)

# print the HTTP header

printHTTPheader()

if len(records) != 0:

# convert the data into a table

table=create_table(records)

else:

print "No data found"

return

# start printing the page

print "<html>"

# print the head section including the table

# used by the javascript for the chart

printHTMLHead("Raspberry Pi Temperature Logger", table)

# print the page body

print "<body>"

print "<h1>Raspberry Pi Temperature Logger</h1>"

print "<hr>"

print_time_selector(option)

show_graph()

show_stats(option)

print "</body>"

print "</html>"

sys.stdout.flush()

if __name__=="__main__":

main()

-- Test URL

Now we can test the URL as

http://192.168.0.2/cgi-bin/sensor.py

Logical Thinking

Pages

Tuesday, March 7, 2017

My Tolerance of Change Scale

Monday, March 6, 2017

Result of my Locus test

Thursday, March 2, 2017

Create a home made temperature sensor using Raspberry pi

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