Solar Heating Control

Overview of Christian Schumann's Solarsystem

Chirstian Schumann's Solarsystem


I have helped Christian Schumann with scripts to control his Solar-panel + rainwater buffer with switches and water-pump.

There are several cronjobs which run every minute, and one of the scripts frequently return “Data error” when reading a DS2890. Reading the sensor second time works almost every time.


Christian Schumann created a quick overview of the system, and I added the temperature’s and sensors in the picture with imagemagick.

Take a look at:


My scripts looks like this when reading the data:


readsensor () (
VAL=`owread -s 3002 $1/$2 2>&1`
[ $ERR != 0 ] &&
# save last value to a file as well (mostly for web-server)
[ "$2" = "temperature" ] && echo "$VAL" > /tmp/last_val.$1.$2
echo "$VAL"

writesensor () (
VAL=`owwrite -s 3002 $1/$2 $3 2>&1`
[ $ERR != 0 ] &&

VAL=`readsensor $SENSOR PIO`
[ $ERR != 0 ] && exit 1


It’s run on a Asus WL500gd with openwrt 0.9.


I have made a simple web-interface to control some switches and potentiometers via cgi-scripts too, but it’s still a major hack and under development.

Perhaps I can show it in a few days. I don’t want to give out the URL to Christian Schumann’s web-interface even if it’s password protected.

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