The DS18B20 is a cheap and accurate temperature sensor. The following commands and scripts wil create a temperature graph on a local website.

Connect sensor to raspberry pi

source: link

You will also need a 4.7 kΩ resistor.

Data to PIN 7 (GPIO4)
Ground to PIN 6
Vcc to PIN 1 (3.3 Volt)

enable the One-Wire interface:

At the command prompt, enter:

sudo nano /boot/config.txt

then add this to the bottom of the file:

dtoverlay=w1–gpio

Exit Nano, and reboot the Pi:

sudo reboot

sudo modprobe w1–gpio
sudo modprobe w1-therm

Write temperature value to csv files:

To find the address of your sensor do:

ls /sys/bus/w1/devices/

For calculating with float values you will need the bc package:

sudo apt-get install bc

The following bash-script reads the value from the temperature sensors and outputs the value to a file.

Filename: write_temp_data.bash
Description: read sensor, and write value with datetime-stamp to file

#!/bin/bash
TT="$(echo "scale=3; `cat /sys/bus/w1/devices/28-0000075e7fa2/w1_slave | tail  -n 1 | cut -d " " -f10  | tr -cd '[[:digit:]]' `/1000" | bc -l )"
DATE=$(date +%Y-%m-%d" "%H:%M) 
echo $DATE $TT
DY=$(date +%Y)
DM=$(date +%m)
FILE="DS_DATA_"$DY"_"$DM".csv"
echo $DATE" "$TT >> $FILE

Create png and copy to website

You will need the gnuplot package:

sudo apt-get install gnuplot

Filename: create_temp_page.bash
Description: generate png from csv file with gnuplot, update the html file with the new image and date

#!/bin/bash
# run as root
 
cd /home/pi/temperature
DY=$(date +%Y)
DM=$(date +%m)
DATE=$(date +%d-%b-%Y+%H:%M)
csvfile="DS_DATA_"$DY"_"$DM".csv"
cp temperature.gnuplot.bkp temperature.gnuplot
sed -i "s/REPLACE/$csvfile/g" temperature.gnuplot
gnuplot <  temperature.gnuplot
cp temperature.png /var/www/html/temperature
cp /var/www/html/temperature/temperature.html.backup /var/www/html/temperature/temperature.html
sed -i "s/DATE/$DATE/g" /var/www/html/temperature/temperature.html

Filename: temperature.gnuplot.bkp
Description: gnuplot template script file

reset
set terminal png size 1200,900 enhanced font "/usr/share/fonts/liberation/LiberationSans-Regular.ttf,8"
set title "raspberry pi temperature sensor"
set xlabel "date/time"
set ylabel "temperature in {\260}C"
set grid
set output "temperature.png"
set xdata time
set timefmt "%Y-%m-%d %H:%M"
set format x "%d/%H:%M"
plot "REPLACE" u 1:3 with lines lc rgbcolor "red" lw 2 title "temperature"

Filename: create_year_graph.bash
Description: At the last day of the month generate a png with all data starting at the beginning of the year

#!/bin/bash
YEAR=`date +%Y`
cd /home/pi/temperature/
 
if [ "$(date --date=tomorrow +\%d)" == "01" ];
then
 
 
  rm DS_DATA_$YEAR"_all".csv
 
  for f in DS_DATA_$YEAR*
  do
    echo $f
    cat $f >> DS_DATA_$YEAR"_all".csv
  done
 
  csvfile=DS_DATA_$YEAR"_all".csv
  cp temperature.gnuplot.year.bkp temperature.gnuplot.year
  sed -i "s/REPLACE/$csvfile/g" temperature.gnuplot.year
  gnuplot <  temperature.gnuplot.year
  mv temperature.png temperature_$YEAR"_all".png
  cp temperature_$YEAR"_all".png /var/www/html/temperature/
fi

Filename: temperature.gnuplot.year.bkp
Description: gnuplot template script file for year graph

reset
set terminal png size 1200,900 enhanced font "/usr/share/fonts/liberation/LiberationSans-Regular.ttf,8"
set title "raspberry pi temperature sensor"
set xlabel "date/time"
set ylabel "temperature in {\260}C"
set grid
set output "temperature.png"
set xdata time
set timefmt "%Y-%m-%d"
set format x "%Y-%m"
plot "REPLACE" u 1:3 with lines lc rgbcolor "red" lw 2 title "temperature"

Website

For the website you will need a webserver with php support.

In short it comes down installing with apt-get:

sudo apt-get install apache2 -y
sudo apt-get install php libapache2-mod-php -y

Then create a temperature folder in your web folder:

cd /var/www/html
sudo mkdir temperature

Filename: temperature.html.backup
Description: html template file

<!DOCTYPE html> 
<HTML> <TITLE></TITLE> 
<BODY> <H1> Temperature graph of Den Haag at DATE</H1> 
<img src="temperature.png"> 
<br>
<center><a href="history.php"> history </a></center>
</BODY> 
</HTML>

Filename: history.php
Description: php file for viewing previous months/years graphs

<?php
echo "<!doctype html>";
echo "<html lang=\"en\">";
echo "<head>";
echo "<title>history</title>";
echo "</head>";
echo "<body>";
echo "<h1>History temperature graph Den Haag</h1>";
$arr = array(".");
$format  = ".png";
 
for($x=0;$x<count($arr);$x++){
    $mm = $arr[$x];
    foreach (glob("$mm/*$format") as $filename) {
 
	if ( strlen($filename) == 24 ){ 
           $monthNum = substr($filename,14,2);
           $monthName = date('F', mktime(0, 0, 0, $monthNum, 10)); 
	   $year=substr($filename,16,4);
           $order[$filename] = $year . $monthNum;
	}
	if ( strlen($filename) == 26 ){ 
	    $year=substr($filename,14,4);
            echo "Jaaroverzicht: <a href=\" ".  $filename ."\">" . $year   . "</a><br>";
	}
    }
}
asort($order);
echo "<BR>";
foreach ($order as $key => $val) {
    $year= substr($val,0,4);
    $monthNum = substr($val,4,2);
    $monthName = date('F', mktime(0, 0, 0, $monthNum, 10));		
    echo "<a href=\" ".  $key ."\">". $monthName . " " . $year   . "</a><br>";
}
echo "<br>";
echo "<a href=\"temperature.html\"> current month </a>";
echo "</body>";
echo "</html>";
?>

Filename: backup_temperature_pic.bash
Description: At the last day of the month: backup the month graph

#!/bin/bash
if [ "$(date --date=tomorrow +\%d)" == "01" ];
then
    month=$(date +%m)
    year=$(date +%Y)
    cp /var/www/html/temperature/temperature.png /var/www/html/temperature/temperature_$month$year.png
fi

Crontab

read/write sensor value every 15 minutes

*/15 * * * * /home/pi/temperature/./write_temp_data.bash

Update temperature webpage every hour

*/60 * * * * /home/pi/luxsensor/./create_temp_page.bash

Update year graph last day of the month

40 21 28-31 * *  /home/pi/temperature/./create_year_graph.bash
55 23 28-31 *  * /home/pi/temperature/./backup_temperature_pic.bash