We now have this sensor, which was originally built for monitoring the awful climate control at my office, set up monitoring MakerSpace instead. The project is a very simple bridge between an inexpensive combined temperature and humidity sensor chip and a computer. The idea is to take frequent measurements of the temperature and humidity in the room and use them to produce graphs.

(photo by Reed Wade)

The project was built on a breadboard to allow it to be altered and new items added on. The controller itself is highly configurable - six pins are directly controllable from the computer with the current software and it can be reprogrammed over the serial port to add more features. I'm still trying to work out what to do with the other half of the breadboard.

An example of the graphs produced is available at http://makerspace.hobby-site.org/~tim/temp.html . The graphs themselves are produced on the connected computer - the computer simply asks for measurements and gets back the individual readings.

There are now eight of these sensors being set up in the Wellington area by different people, though this one is the only one to be fully assembled so far. Other people are planning to use this as a base to control external hardware to manage the climate as well as sensing it. In MakerSpace it's more likely to be extended to act as a more general computer to device bridge.

This project consists of an Atmel ATMEGA-8 microcontroller, MAX232 to drive the serial port lines, a cheap clone of the Sensirion humidity and temperature sensors, and a few passive components. The code is written in C for the open source AVR-GCC toolchain and is itself open source. It runs off a 5V supply, in this case taken from a USB cable. It doesn't use that for communication - it talks to the computer's serial port.

More detailed hardware instructions will probably be put together while the other sensors are being assembled. To obtain the code used by this, you can install the git version control system and run:
git clone git://goddard.net.nz/temp_sens