RaspberryPi Temperature Sensor

Time to build a temperature sensor with my Pi.

Schematics

Configure the Pi

Update the OS

This not necessary, but generally a good idea.

apt-get update
apt-get ugrade

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

Check setup

Check whether there is now our sensor device:

cd /sys/bus/w1/devices
ls -1

10-000802ad5087
w1_bus_master1

See it's content (values):

cd 10-000802ad5087
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

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 "set key inside right top vertical Right noreverse enhanced autotitles columnhead nobox" >> "${GFILEPLOTCOMMANDS}"
echo "set timefmt \"%H:%M\"" >> "${GFILEPLOTCOMMANDS}"
echo "set xdata time" >> "${GFILEPLOTCOMMANDS}"
echo "set format x \"%H:%M\"" >> "${GFILEPLOTCOMMANDS}"
echo "set style data lines" >> "${GFILEPLOTCOMMANDS}"
echo "set xtics \"01:00\" rotate by 90 offset 0,-2 out" >> "${GFILEPLOTCOMMANDS}"
echo "set title \"Temperature on day ${GTIMESTAMPDATEHUMANREADABLE}\"" >> "${GFILEPLOTCOMMANDS}"
echo "set ylabel \"°C\"" >> "${GFILEPLOTCOMMANDS}"
echo "set xlabel \"Time\"" >> "${GFILEPLOTCOMMANDS}"
echo "set yrange [ 0.000 : ] noreverse nowriteback" >> "${GFILEPLOTCOMMANDS}"
echo "set term svg" >> "${GFILEPLOTCOMMANDS}"
echo "set output \"${GFILEGRAPH}\"" >> "${GFILEPLOTCOMMANDS}"
echo "plot \"${GFILELOG}\" using 1:2 title 'Temperature'" >> "${GFILEPLOTCOMMANDS}"
cat "${GFILEPLOTCOMMANDS}" | gnuplot 

You might want to use a cronjob like this:

*/15 * * * *    /home/pi/Development/temperature/readTemperature.sh > /dev/null 2&>1

And this is how it looks:

---

• 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: dpkg-reconfigure tzdata
  • 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 well be used: Tomat-O-Mat
  • More about Raspberry Pi on this website
• Footnotes: