Cool. That RTD converter should be fine. Another great place for sensors and stuff is Omega.com They'll send you ton's of huge catalogs for nothing :D If you need any help programming the logo's, let me know. We have a few here that I have installed lately (read:6) and im gettin pretty good at it LOL

As far as wireless communication, on a budget, I dunno :( would like to get one of their communication modules to see what can be done there...

Hey banditpowdercoat;

Which PLC based product did you purchase ??

If its the Arduino, check out - http://reefprojects.com/wiki/Main_Page. Its all open source !!

I got a few Siemens Logo's for now

That looks pretty interesting, and would actually be pretty fun to set up. But after adding up all the parts you need, board, clock, IO, relays,LED's etc. I think the logo is still a far cheaper system. The big drawback is having to pick up relays for switching, the logo contacts are good for up to 10A each, so that'd power 1200W of lighting.
I picked up my logo for $50 shipped, with the software included. I already had the programming cable, but they are new for $40 usually... but i've seen them under $20 on EBay. i'm either going to butcher a laptop charger for the power supply, or use a power supply out of an old computer, i only need 1A at 12V-24V, so both are far overpowered, giving me extra capability for addons. I got a thermocouple+transmitter for $20 off eBay(notice a trend?), and other than that, its all set up.

I do like the idea with the Arduino, VERY custumizable, and with the C++ programming, it wouldn't be hard to make a nice PC program to monitor everything.

Maybe i should buy a bunch of LOGO's and start selling custom tank PLC setups, that could be the ticket to a much bigger tank :D

If you want good, cheap PLC stuff check out here:

http://www.automationdirect.com/adc/...e_Micro_Brick)

And if your looking for ideas on automation or the Arduino check out my webpage as im very deep into my own fully automated tank and controller:

http://richardorme1979.googlepages.com/home

If you would like any help give me a shout!!

VR