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December 04, 2007

1-Wire Environmental Monitoring

I have a sensor network I use for monitoring environmental conditions around my apartment. Here's how I did it.

To start with, I use a 1-wire network to connect several sensors for monitoring. I use Maxim/Dallas DS1920 Temperature iButtons and AAG Electronica TAI8540B Humidity Sensors for the indoor sensing. Outdoors I use a Hobby Boards Humidity/Temp/Solar Sensor in a Davis 7714 Solar Radiation Shield. The sensors are simply connected with telephone cabling. The internal iButtons are mounted to Maxim/Dallas DS1402D-DR8 Blue Dot Receptacles and the Humidity sensors are pre-cabled. A Maxim/Dallas DS9097U-009 adapter provides a serial interface to the 1-wire network and is connected to my server machine. Incidently, all these sensors are parasitically powered from the 1-wire network solely by attempting to read from them. On my server machine I periodically run the DigiTemp software to poll each sensor and store the results in an RRD (Round Robin Database) using RRDtool. I then use RRDtool again to periodically plot the data and produce the graphs displayed. System temperatures are garnered from the onboard motherboard sensors using xmbmon.

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