View source for RaspberryPi Temperature Sensor

Time to build a temperature sensor with my [[Pi]].

=== Schematics ===
[[Image:RaspberryPiDS18B20.png|300px]]<br>''Remember that the [[Pi]] revisions have different pinouts! This will work for Revison 2, that is board revision 0004''<ref>[[Raspberry Board Revision Check]]</ref>. If you also want to measure humidity and don't need decimal degrees, take a look at [[RaspberryPi Humidity and Temperature Sensor]] which uses a [[DHT11]] instead of a [[DS18B20]]. But the [[DHT11]] has another disadvantage: There's no kernel module for the [[Pi]] for the [[DHT11]] for [[1-wire]].

=== Configure the [[Pi]] ===
==== Update the OS ====
This not necessary, but generally a good idea.
 apt-get update
 apt-get upgrade

==== Install missing packages ====
If you have already installed them, you can skip this step.
 apt-get install bc
 apt-get install gnuplot

==== Setup kernel modules for GPIO and 1-wire device ====
 modprobe w1-gpio
 modprobe w1-therm
That maps <tt>/sys/bus/w1</tt>, you might want to do: <tt>vi /etc/modules</tt> and add the modules

==== Check setup ====
Check whether there is now our sensor device:
 cd /sys/bus/w1/devices
 ls -1
(if not you might want to try adding <tt>dtoverlay=w1-gpio</tt> to <tt>/boot/config.txt</tt> and reboot)

 10-000802ad5087<ref>This will differ, since this is the UID of my device.</ref>
 w1_bus_master1

See it's content (values):
 cd 10-000802ad5087<ref>This will differ, since this is the UID of my device.</ref>
 cat w1_slave

 39 00 4b 46 ff ff 03 10 9c : crc=9c YES
 39 00 4b 46 ff ff 03 10 9c t=28562<ref>This is the temperature in degrees celsius (multiplied by 1000), therefore I have 28.562°C in my living room. OMG! It's frickin' hot!</ref>

=== Code ===
This is how I read the device and generate a nice plot using GNUplot:

 #!/bin/bash
 #set -x
 #
 # Script: readTemperature.sh
 # Author: Heiko Kretschmer
 # Purpose: Reading the temperature and generating a nice plot
 #
 #
 
 #
 # Globals
 #
 GDEVICEID="10-000802ad5087"
 GDEVICESPATH="/sys/bus/w1/devices"
 GDEVICEVALUEFILE="w1_slave"
 GTIMESTAMPFORMAT="%Y-%m-%d_%H:%M"
 GTIMESTAMP="`date +${GTIMESTAMPFORMAT}`"
 GTIMESTAMPTIME="`date '+%H:%M'`"
 GTIMESTAMPDATE="`date '+%Y-%m-%d'`" # ISO 8601 date format
 GTIMESTAMPDATEHUMANREADABLE="`date '+%A, %Y-%m-%d'`"
 GFOLDERBASE="/home/pi/Development/temperature"
 GFOLDERLOGS="${GFOLDERBASE}/logs"
 GFOLDERGRAPHS="${GFOLDERBASE}/graphs"
 GFOLDERTMP="${GFOLDERBASE}/tmp"
 GFILELOG="${GFOLDERLOGS}/readTemperature_${GTIMESTAMPDATE}.log"
 GFILEGRAPH="${GFOLDERGRAPHS}/readTemperature_${GTIMESTAMPDATE}.svg"
 GFILEPLOTCOMMANDS="${GFOLDERTMP}/readTemperature-plot.cmd"
 
 #
 # Main
 #
 
 # Init
 test ! -d "${GFOLDERLOGS}" && mkdir "${GFOLDERLOGS}"
 test ! -d "${GFOLDERGRAPHS}" && mkdir "${GFOLDERGRAPHS}"
 test ! -d "${GFOLDERTMP}" && mkdir "${GFOLDERTMP}"
 
 # Get the temperature
 VALUERAW="`cat \"${GDEVICESPATH}/${GDEVICEID}/${GDEVICEVALUEFILE}\" | grep t= | cut -d= -f2`"
 VALUE="`echo \"scale = 3; ${VALUERAW} / 1000\" | bc`"
 #echo Temperature: ${VALUE}
 
 # Write it into the log (one logfile per day to get nice graphs)
 echo -e "${GTIMESTAMPTIME}\t${VALUE}" >> "${GFILELOG}"
 
 # Generate the graph
 test -f "${GFILEPLOTCOMMANDS}" && rm "${GFILEPLOTCOMMANDS}"
 echo "reset" >> "${GFILEPLOTCOMMANDS}"
 echo "set key inside right top vertical Right noreverse enhanced autotitles columnhead nobox" >> "${GFILEPLOTCOMMANDS}"
 
 # Set time format for X axis
 echo "set timefmt \"%H:%M\"" >> "${GFILEPLOTCOMMANDS}"
 echo "set xdata time" >> "${GFILEPLOTCOMMANDS}"
 echo "set format x \"%H:%M\"" >> "${GFILEPLOTCOMMANDS}"
 
 # Setup line style (#1) for the temperature line
 echo "set style line 1 lc rgb '#8b1a0e' pt 1 ps 1 lt 1 lw 2" >> "${GFILEPLOTCOMMANDS}" # http://www.gnuplotting.org/tag/grid/
 echo "set style data lines" >> "${GFILEPLOTCOMMANDS}"
 
 # Set X tics (one tic per hour, rotate that tick-labels by 90 deg and move em a bit)
 echo "set xtics \"01:00\" rotate by 90 offset 0,-2 out nomirror" >> "${GFILEPLOTCOMMANDS}"
 
 # Setup Grid (with line style #12)
 echo "set style line 12 lc rgb '#E0E0E0' lt 0 lw 1" >> "${GFILEPLOTCOMMANDS}" # http://www.gnuplotting.org/tag/grid/
 echo "set grid back ls 12" >> "${GFILEPLOTCOMMANDS}" # http://www.gnuplotting.org/tag/grid/
 
 # Setup Title
 echo "set title \"Temperature on ${GTIMESTAMPDATEHUMANREADABLE}\"" >> "${GFILEPLOTCOMMANDS}"
 
 # Label X and Y Axis
 echo "set ylabel \"°C\"" >> "${GFILEPLOTCOMMANDS}"
 echo "set xlabel \"Time\" offset 0,-0.5" >> "${GFILEPLOTCOMMANDS}"
 
 # Setup Y range
 echo "set yrange [ 0.000 : ] noreverse nowriteback" >> "${GFILEPLOTCOMMANDS}"
 
 # Set output file type to svg and plot it into file
 echo "set term svg size 640,480" >> "${GFILEPLOTCOMMANDS}"
 echo "set output \"${GFILEGRAPH}\"" >> "${GFILEPLOTCOMMANDS}"
 echo "plot \"${GFILELOG}\" using 1:2 title 'Temperature' with l ls 1" >> "${GFILEPLOTCOMMANDS}"
 cat "${GFILEPLOTCOMMANDS}" | gnuplot

You might want to use a cronjob like this:
 */15 * * * *    /home/pi/Development/temperature/readTemperature.sh > /dev/null 2>&1

=== Resulting graph ===
And this is how it looks:<br>
[[Image:RaspberryPiTemperaturePlotExample.svg|No, there's no mistake, it was veery hot in my living room all night and all day, until a lightning storm came]]

----
* More like this
** [[RaspberryPi Humidity and Temperature Sensor]]
** [[Tomat-O-Mat]]
* Links
** Where I got the ideas from: http://www.raspberrypi-spy.co.uk/2013/03/raspberry-pi-1-wire-digital-thermometer-sensor/
** Where I learned to use xticks: http://psy.swansea.ac.uk/staff/carter/gnuplot/gnuplot_time.htm
** Nice to know: How to setup timezones: <tt>dpkg-reconfigure tzdata</tt>
** About various methods of connecting 1-wire devices: http://www.fhemwiki.de/wiki/Raspberry_Pi_und_1-Wire and http://blog.gegg.us/2013/03/4-different-methods-of-1-wire-access-on-raspberry-pi/
** Where this will be used: [[Tomat-O-Mat]]
** [[:Category:RaspberryPi|More about Raspberry Pi on this website]]
* Footnotes:
<references/>


[[Category:Development]]
[[Category:RaspberryPi]]