Ed Mallon blogged about his DIY ProMini data logger build:
Typical pro-mini loggers built with this design sleep at 0.25mA, before extra sensors are added. At that current draw, the logger should deliver approximately six months of operation on three brand new AA batteries with a 15min duty cycle; depending on sensor load.
We started the new year with another collaborative project, and the folks at the other uni. suggested that the project blog had become a bit of a spaghetti monster, which they had a hard time searching through.
So I produced a short summary page with links to all of the build instructions in a (more or less) logical order:
https://edwardmallon.wordpress.com/how-to-build-an-arduino-data-logger/
Hope that helps anyone out there who needs a few cheap loggers for their next research project!