Temperature… The beginnings…

Arduino, Electronics, Raspberry PI, Temperature

Pieces used:

  • Raspberry Pi.
  • Dallas 18B20 temperature sensor.
  • Prototyping board and random bits of wire.
  • Remote Debian server with a LAMP style setup

    The basic process flow:

    A cron job on the PI collects the current temperature from the 18B20 chip attached to the GPIO. It then inserts the temperature into a remote MySQL database on the big server. A cron job on the big server creates a PNG from the data using rrdtool. There is a link in the web directory to the PNG, which you see above.

    Here is the table creation commands.


    CREATE DATABASE temp_monitor;

    USE temp_monitor;

    CREATE TABLE `temp_data` (
    `id` bigint(20) NOT NULL AUTO_INCREMENT,
    `unixtimestamp` int(11) NOT NULL,
    `temp_f` float NOT NULL,
    `temp_c` float NOT NULL,
    `sensor` varchar(25) NOT NULL,
    `adjusted` int(11) DEFAULT NULL,
    PRIMARY KEY (`id`)
    );

    Here is the cron job on the rPI that reads the temp and sends it to the big server in the sky.

    #!/usr/bin/python

    import time;
    import httplib

    # Exampe temperature file output:
    # —————————————–
    # 77 01 4b 46 7f ff 09 10 6f : crc=6f YES
    # 77 01 4b 46 7f ff 09 10 6f t=23437
    # Config options:
    # Temperature “file”
    pin=0
    device=”28-00000441aeff”
    tempfile = “/sys/bus/w1/devices/”+device+”/w1_slave”
    outputfile = “/tmp/newtemps”

    # Get the temperature
    tfile = open(tempfile)
    text = tfile.read()
    tfile.close()

    # Split the text with new lines (\n)
    # and select the second line.
    secondline = text.split(“\n”)[1]

    # Split the line into words, referring to the spaces,
    # and select the 10th word (counting from 0).
    temperaturedata = secondline.split(” “)[9]

    # The first two characters are “t=”, so get rid of those
    # and convert the temperature from a string to a number.
    temperature = float(temperaturedata[2:])

    # Put the decimal point in the right place and display it.
    temperature = temperature / 1000

    # Convert to fahrenheit
    ctemp = temperature;
    temperature = 32 + ( temperature * 9 ) / 5

    # Get time
    ut = time.time()
    localtime = time.localtime(time.time())

    #Output
    outline = ‘{} {} {} {} {} {} {}\n’ . format(localtime[0], localtime[1], localtime[2], localtime[3], localtime[4], localtime[5], temperature)

    ofile = open(outputfile, “a”)
    ofile.write( outline )
    ofile.close()

    # send the temp to the server
    conn = httplib.HTTPConnection( “database.myserver.org”)
    conn.request(“GET”, “/sensor_input.php?c=” + str(ctemp) + “&s=28-00000441c8b3&t=” + str(ut))
    r1 = conn.getresponse()

    Here is the PHP code that accepts the data from the PI and stuffs it into the DB.


    // inputs:
    // Required:
    // c = temp in celcius
    // s = id of sensor providing the data
    //
    // Optional:
    // t = unix time stamp. If this does not exist use NOW()
    //

    function error_out() {
    print “Something is missing.&th;br>&th;pre>\n”;
    print_r($_REQUEST);
    exit();

    }

    function clean($in) {
    return preg_replace(“/[^A-Za-z0-9\.]/”, ”, $in);
    }

    if( isset( $_REQUEST[‘c’] ) ) {
    $c = clean( $_REQUEST[‘c’] );
    $f = ( ( $c * 9 ) / 5 ) + 32;
    } else
    error_out();

    if( isset( $_REQUEST[‘s’] ) )
    $s = clean( $_REQUEST[‘s’] );
    else
    error_out();

    if( isset( $_REQUEST[‘t’] ) )
    $t = clean( $_REQUEST[‘t’] );
    else
    $t = ‘NOW()’;

    // For some reason we periodically get two known bogus numbers
    // 185’f and 32.1116’f. So we are going to toss them out
    // even if on the off chance they were valid.

    if( $f == 185 or $f == 32.1116 )
    exit;

    $query = “INSERT INTO temp_data ( unixtimestamp, temp_c, temp_f, sensor ) ” .
    ” VALUES ( $t, $c, $f, ‘$s’ )”;

    $link = mysql_connect(‘localhost’, ‘fakeUser’, ‘fakePassword’)
    or die(‘Could not connect: ‘ . mysql_error());

    mysql_select_db(‘temp_monitor’) or die(‘Could not select database’);

    // Performing SQL query

    $result = mysql_query($query) or die(‘Query failed: ‘ . mysql_error());

    And here are the cron jobs on the big server that creates the image.

    Runs every minute.

    #!/bin/bash
    cd /var/www

    F_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’2800000441c8b3′”

    C_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’28dfca4140090′”

    rrdtool graph daily.png –imgformat=PNG –start=-1day –end=now –width=400 –height=200 \
    “DEF:temp_f=$F_BASE:min:AVERAGE” \
    “LINE1:temp_f#FF0000:Office” \
    “GPRINT:temp_f:MIN:Min\: %6.2lf” \
    “GPRINT:temp_f:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_f:MAX:Max\: %6.2lf” \
    “GPRINT:temp_f:LAST:Last\: %6.2lf” \
    “DEF:temp_c=$C_BASE:min:AVERAGE” \
    “LINE1:temp_c#00FF00:Remote” \
    “GPRINT:temp_c:MIN:Min\: %6.2lf” \
    “GPRINT:temp_c:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_c:MAX:Max\: %6.2lf” \
    “GPRINT:temp_c:LAST:Last\: %6.2lf”

    rrdtool graph weekly.png –imgformat=PNG –start=-1day –end=now –width=400 –height=200 \
    “DEF:temp_f=$F_BASE:min:AVERAGE” \
    “LINE1:temp_f#FF0000:Office” \
    “GPRINT:temp_f:MIN:Min\: %6.2lf” \
    “GPRINT:temp_f:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_f:MAX:Max\: %6.2lf” \
    “GPRINT:temp_f:LAST:Last\: %6.2lf” \
    “DEF:temp_c=$C_BASE:min:AVERAGE” \
    “LINE1:temp_c#00FF00:Remote” \
    “GPRINT:temp_c:MIN:Min\: %6.2lf” \
    “GPRINT:temp_c:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_c:MAX:Max\: %6.2lf” \
    “GPRINT:temp_c:LAST:Last\: %6.2lf”

    Runs every hour.

    #!/bin/bash
    cd /var/www

    F_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’2800000441c8b3′”

    C_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’28dfca4140090′”

    rrdtool graph monthly.png –imgformat=PNG –start=-1day –end=now –width=400 –height=200 \
    “DEF:temp_f=$F_BASE:min:AVERAGE” \
    “LINE1:temp_f#FF0000:Office” \
    “GPRINT:temp_f:MIN:Min\: %6.2lf” \
    “GPRINT:temp_f:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_f:MAX:Max\: %6.2lf” \
    “GPRINT:temp_f:LAST:Last\: %6.2lf” \
    “DEF:temp_c=$C_BASE:min:AVERAGE” \
    “LINE1:temp_c#00FF00:Remote” \
    “GPRINT:temp_c:MIN:Min\: %6.2lf” \
    “GPRINT:temp_c:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_c:MAX:Max\: %6.2lf” \
    “GPRINT:temp_c:LAST:Last\: %6.2lf”

    Runs every day.

    #!/bin/bash
    cd /var/www

    F_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’2800000441c8b3′”

    C_BASE=”sql//mysql/host=127.0.0.1/dbname=temp_monitor/username=fakeUser/password=fakePassword//temp_data/unixtimestamp/temp_f/sensor=’28dfca4140090′”

    rrdtool graph yearly.png –imgformat=PNG –start=-1day –end=now –width=400 –height=200 \
    “DEF:temp_f=$F_BASE:min:AVERAGE” \
    “LINE1:temp_f#FF0000:Office” \
    “GPRINT:temp_f:MIN:Min\: %6.2lf” \
    “GPRINT:temp_f:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_f:MAX:Max\: %6.2lf” \
    “GPRINT:temp_f:LAST:Last\: %6.2lf” \
    “DEF:temp_c=$C_BASE:min:AVERAGE” \
    “LINE1:temp_c#00FF00:Remote” \
    “GPRINT:temp_c:MIN:Min\: %6.2lf” \
    “GPRINT:temp_c:AVERAGE:Avg\: %6.2lf” \
    “GPRINT:temp_c:MAX:Max\: %6.2lf” \
    “GPRINT:temp_c:LAST:Last\: %6.2lf”

Leave a Reply