I think one of the common questions would be how much did it all cost? There's no simple answer to this one, but I'll try to shed some light on the topic.

       

        The most expensive will be the house to control :D

        Having said that, right now I'm 'stuck' in Korea living in a hotel room, and even with that there's plenty to play with, so maybe the house is not really necessary. My hotel is pretty civilised and the lights and AC are remotely controlled, and obviously so is the TV, it's only a matter of time when they will succumb to my power *evil grin*. I have my mobile workshop with me.

        So, seriously, the most expensive bit is the Mac running the server. It can be anything from an old PowerPC MacMini running 10.5 Leopard or Tiger 10.4 to a full blown XServe. I was running it on an old iMac G5 and recently moved to a first generation Intel MacMini with 2GB RAM and upgraded 2.0GHz dual core CPU. It doesn't even sweat.

        Next thing you'll gonna need is an Arduino board, you need one for a start but you will probably quickly find a need for more. I use five: 2 Mega boards, one for inputs, one for outputs. This is a bit of an overkill but the price difference between Mega and Duemilanove which I should really use is negligible for me. The software running on Megas is the same, so it's ok to have just one - I have two so I don't have to worry about queueing holdups when executing actions while the probes are being pooled. Then theres 3rd Arduino which is pooling the 'realtime' inputs, it is running a different software and feeds the server with data from PIRs, and things like wall buttons, RF remotes, door and windows sensors and the like. The last 2 are Nano boards living in a breadboard, I use those for R&D. I have two so I could use one as a receiver and the other as transmitter when I was playing with IR control libraries and my RF controlled light switches.

        Cabling - just get a box of Cat6 from eBay and a 100m roll of telephone cable, it will last forever (or long enough :).

        Sensors and misc electronic components - eBay is your best friend forever. Regardless of where you are, unless you're in Italy that is :P, you shouldn't have any problems buying your stuff from anywhere. Some of the goodies I source from UK where I normally live, but I was also buying from Poland, Bulgaria or Romania (never remember which, my relay boards are from there), Thailand, Hong Kong, probably others I don't remember, and of course China.

Some stuff to search on eBay or google for: DS18B20, DS18S20, DS2438, Sharp IR sensor, LDR, PIR, SHT-12, relay board, 12V power supply, breadboard, resistors, capacitors.

Tools is where you will shine if you like to spend a ridiculous amounts of money on unnecessary goodies. You can go completely bonkers and get yourself a full blown electronics workshop, maybe with a 3D printer as well.

But a humble soldering station from Maplin is a good start, at least it was for me. What is very handy is a portable soldering iron such as this or this. There's no connection like soldered connection. Battery powered iron is much easier and safer to work with, but not nearly as powerful as the gas powered. I have both, and recommend the battery one for a start, just get the most powerful you can. I upgraded my Maplin soldering station to used Metcal MX500, it's a great tool and makes a difference for the precision work, but it is not that many times better than the Maplin to justify the price.

If you have a house with loft a head light is also a must, I got mine way too late, couldn't live without  one now.

Did I mention a multimeter already? Well you need one, and learn how to use it, don't spend too much time figuring out which one to buy, the differences between them are not that important so buy on the looks alone (don't tell your wife). If you really want to spend a bit more get one with auto-sensing as it makes your life easier.

If you think that installing an intelligent home system is going to save you money, think again. It's got some potential for savings in energy bills due to efficient scheduling and such, but running the server and electronics 24/7 will probably counter that straight away, and it will never pay for the installation costs, let alone the time you will have to invest to build it. Lots of time - but for me it's a hobby, I'm having loads of fun and I learn a lot, so it is definitely worth it and I couldn't recommend it more. One thing to remember is that you will most probably spend the money over considerable stretch of time, so it should be easily bearable.

I was thinking about having a nice table with all the prices here, but decided not to, firstly because it all changes too rapidly and prices vary from country to country anyway, but mostly because I have better things to do ;) Just google and find for yourself, the bottom line is that it can be quite expensive but doesn’t have to be if you spend some effort optimising your purchases.