Paul Hubbard pfhubbard@ucsd.edu April 19 2010 This project is Arduino and Python/Twisted code to implement a simplest- possible 'office weather station' that presents temperature and relative humidity readings via a webserver interface. The sensors are: * LM35CAZ Nice, TO-92 cased, temperature sensor with 0-5VDC output and no external components required. A few bucks from National. http://www.national.com/mpf/LM/LM35.html#Overview * Ohmic Instruments SC-600 humidity sensor and signal conditioning module. http://www.ohmicinstruments.com/pdf/SC-600.pdf About $15, quite cheap for a sensor this nice. You need an external RC lowpass, so two more components in the circuit. See the PDF. Here's a picture: http://github.com/phubbard/office-weather/raw/master/sensors.jpg Software: * The Arduino sketch simply sends the two ADC counts, as integers, on a single text line once per second, nothing else. * The Python code, implemented as a Twisted app, uses their LineReceiver class to get notifications of each new line, after which it does the parsing, linearization and units. Overkill but simple. The twisted code also adds a simplest-possible HTTP interface, running on port 2000. The format used is designed for ingestion into Cacti, for nice time-based RRD graphs. Notes: * The Mac Mini I'm using to host this has to have the Arduino drivers in place to use the virtual serial port for communications. * I'm debating an ethernet shield, but $50 seems overpriced for now.