I don't think I'm ready to make a pHduino, but...

What do you all think about trying to interface with this?

http://www.indoorgarden.com/store/images/716572.jpg

I'd like to be able to log the data/automate based on it, and I can't find anything like that off-the-shelf.

Am I nuts?

No, you're not nuts - ambitious, but not nuts...

Being able to interface to it will depend on whether you can identify the control circuitry within the device; there may be identifiable parts, or there may just be some black epoxy blobs on-board. Even after you have an idea about the parts (assuming this is possible), you may still find it a difficult going.

What you might do is contact the manufacturer of the device (before purchase?):

http://www.controlwizardproducts.com/

(wow - those are expensive!)

Be honest and upfront with your intentions to interface with it - maybe they will be interested in what you plan to do, and give you details on the inner workings of the device to allow you to do it (maybe there is an on-board calibration port?)...

With that said, though - such "bare" sensors should be possible to find otherwise, though you would have to write all of the software necessary to display their measurements (plus calibration, etc). Googling for "pH sensor component" might turn up something, but you might have to do some digging.

Another possibility might be hacking a digital pregnancy test kit; they are basically pH meters (more or less), but then again they may not work the way you are expecting (just an idea to look into, though).

Finally; Forrest M. Mims III wrote a mini-notebook called "Engineer's Mini-notebook: Environmental Projects" (Radio Shack 1995):

http://www.forrestmims.org/

He also had another on Sensors. Both are out of print at RS, but at one time he published it elsewhere; I also know it is possible to find copies other ways (used bookstores, etc). His entire series is worthwhile to find for your collection, BTW.

Good luck!