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This project started as a way to monitor the temperature in my apartment because I was concerned that my landlord wasn't providing enough heat in the winter.  It grew into a computer-controlled network of temperature sensors with the ability to expand to measure many different types of properties.

This system is based upon the Dallas Semiconductor line of 1-wire devices.  These particular devices were chosen for their ease of use; minimal additional components are required for robust functionality.  The following design elements were included:

  • Communication to host system via RS-232 interface
  • Capable of providing a couple hundred mA to devices on the network
  • Communication over standard ethernet cable
  • Linux interface software

The RS-232 interface was chosen for simplicity in programming and interface; it has been around for ages, is well understood, and the hardware is inexpensive.  A self-powered design was chosen over host computer power for the ability to drive more devices over a larger network.  For economical reasons, standard ethernet cable was chosen as the network medium, even though only one or two pairs are used.  Finally, a Linux interface was decided upon for maximum versatility and ease of use.  I'm sure that the interface software could be ported to Windows fairly easily, but my Linux box is on all the time while the Windows box is shut off every evening.

Copyright © 2004 Michael Shevlin
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