Thanks a lot for posting this great project! I feel the same way about sharing. If you want a copy of my CO2 controller code, let me know. Easy interface with any CO2 sensor: I used the analog out of my NOSE monitors (with humidity, temp, CO2 & webserver built in) to control a relay for fan & CO2 burner or tank. I think it would be a nice addition to your project.
Thanks again for posting -I'm just beginnning to read the posts but had to post on your comment about sharing. I'd love to see some open source grow software. Not just Arduino but PC too.
Damn - Now I'm going to be up all night...
DX
PS - Here's a link to the NOSE monitor page. Not like you need the temp/humidity but it's nice to be able to check status via the webserver.
If you want one of the modules for half price, let me know.