computer controlled greenhouse

hi i want to make a computer controlled greenhouse and need to know if i buy a usb temperature sensor and a usb relay can i get software to make them work together. so if my greenhouse gets to 25degrees the seperate relay will switch on to open the windows. any help grateful or anyone made something similar that is wiling to help. thanks

 

Bayliss autovents - much easier!
http://www.baylissautovents.co.uk/

Motorised openers for greenhouse windows not easy - particularly if you want them to close fully in Winter so as not to let heat escape.

 

Search for Greenhouse automation using your chosen search engine and a whole world opens up. From PC based systems to independent units for all sizes. Personally I wouldn't tie up a PC I'd go for a PLC based system and only if I wanted to control temperature, lighting and nutrition.
I'm with Kristen and find autovents work very well.

 

We're trying to fit some automated vents to a conservatory. The mechanics for the openers are way more complex than I would like (or trust!) compared to the old rack & pinion systems ... but ... they were linked to all windows, so a single control (rotate with an handle, or motor) opened/closed all simultaneously, and as the gears wore some windows would shut sooner than others and they were never all tightly shut (the force to do that would probably buckle the frame before it closed the last window!)