The House Computing System at 5 Fran Court


Since about 2000, there has been a "house computer" at 5 Fran Court, controlling various home mechanisms automatically. These mechanisms are largely confined to watering and heating systems, but other functionalities have been, are, or will be operational as well.

Early in Jan 2015, while we were out of the country, there was a catastrophic failure of the system. Details of exactly what went wrong are not clear, but I came home to an exploded laptop battery (in the relay driver system, ringwood), and a dead CF card (inside the data logging system, garedelyon). Attempts to rebuild and restart these systems were not very successful, and the decision was made to replace them both (and some other miscellaneous functions) with a new BeagleBone Black (BBB) system, given to me as a Christmas present by my son Nathan (who wrote the original system).

Several issues have arisen as a consequence:

  1. The data logging devices are old, and have only RS232 interfaces. The new BBB system has only USB inputs.
  2. The BBB has only one server USB connection. A powered hub is necessary to serve all the data devices.
  3. The BBB does not come with a general purpose web server, nor an Arduino development interface. Both of these have had to be developed. In the case of the web server, the decision to migrate to a Flask-based system was also taken.

It is intended that as the new BBB system has all the attributes necessary to support fully the entire house computer system, it will be used to host all house computer functionality, and will replace 3 existing systems. These include (see also the house computer documentation ):

  1. A web server to provide user functionality to control the house system.
  2. A system to monitor the house temperature, and to turn the house heating on and off to control this temperature.
  3. A data logging system for the rainwater tanks to measure and record the water levels over time.
  4. A data logging system for the solar panels to measure and record solar energy input to the house UPS.
  5. An Arduino interface to drive all the relays controlling the various house functions.
  6. The relay control subsystem, allowing turning on and off the various house devices, and to run them for a preset time.
  7. A generalized RPC interface to access all the above functionality.

Progress to date (4 Apr 2015):

  1. The BBB now supports an Apache2 web server, serving all these personal pages (attribute 1 above).
  2. It is also running a Flask web server, developed mainly to take over the house computer web page (attribute 1 above).
  3. The powered hub is installed and operational (parts of attributes 2,3,4 above).
  4. The Arduino susbsystem is operational (attribute 5 above).
  5. The relay control subsystem is operational (attribute 6 above).
  6. The RPC interface is operational (attribute 7 above).


cron jobs
Every 5 minutes a dimboola cron job under account ajh runs the program /Users/ajh/bin/, which in turn runs the jobs:
See below for further details on these jobs.
The log of house temperatures is maintained in a file /circuit-dir/temp.log kept on central. A cron job runs the program /Users/ajh/bin/, which
  1. rsyncs the temp.log file to dimboola, and then
  2. runs /Users/ajh/Personal/Home/Heating/, which creates a new tempplot.png file, which is
  3. (re)linked to the web file /Users/ajh/Sites/personal/tempplot.png
This latter file is accessed and displayed by various web pages.


water tank level
Every day at midnight, a cron job on central under account ajh runs the program /home/ajh/bin/ 10, which turns on the wootank to plastank valve for 10 minutes (the parameter 10). Currently this is disabled (commented out). Revision: it has been re-enabled, with a slightly different cron job schedule.


garedelyon is a low-power microcomputer running Linux. It is intended to take over the operations of central, since it is low power and noiseless. However, restrictions on hardware have seen this migration process stall somewhat, and it needs a concerted effort to restart the migration. To date, only weather station data and water tank logging have been migrated.

weather station
This function reads the TRS80 WX200 weather station device on demand. It is accessible by running the program /usr/bin/wx200py, which can also be called remotely.
water logging
The water logging relies upon an RS232 port, /dev/ttyUSB0, which must be initialised with XON/XOFF flow control. (See the script / This is locally developed circuit uses a capacitance bridge that is sensitive to the water level, and transmits every minute a new reading. The reading must be calibrated to give water level in appropriate units, and this is done by some user level software. Data is logged to the file /water.log


If for any reason garedelyon must be restarted, you will need to restart the weather daemon (/usr/sbin/wx200d), as well as the water logging subsystem. This latter has a script / to shut down and restart the water logging in an orderly way.

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