Pauly, Wildbill and PaulRB,
Thank you for your ideas and comments.
Pauly,
If I have trouble with my wired system, I will look into the jeenodes.
wildbill,
I will go with the Mega for the project but, I may also get a Uno for some of the testing, and I can always think of something else to do with it later.
I had not thought of the wire runs. The shortest is about 30 ft. and the longest is about 75 ft. and they run in 3 different directions. I was very particular in locating each sensor. The cable looks like regular 4-wire telephone cable. I looked at my information on the original equipment and it says "RC low-pass filter on each signal line" so I'll open it up and see what method they used. There is a small junction box that ties the three telephone-like lines to an 8-conductor cable that feeds the console. Since I have not had any sporadic readings in about 14 yrs. I would guess that their method is Ok. But, that's not saying it won't be a problem with Arduino.
I certainly agree with your break it into pieces and start small approach.
My next step before placing a parts order is to decide on my LCD layout, I am thinking of probably a 4X20 LCD with current conditions and a switch to cover daily highs and lows.
I will include the ethernet shield in my orders but, that will probably be the last part to be programmed.
Pretty agressive for a guy who knows very little about programming!
Paul,
I like the specs on the barometer and humidity sensors, I will use them for my project. Interestingly, I had already selected the same clock module.
Again thank you for your thoughts and advice.
Willy45