I'm using Arduino for some months and have a lot of fun, I'm learning electronics this way.
I already control some stuff in our farm based (some time) on temperature. I'm using Dallas DS18B20.
Now, I'm looking to control heating light based on temperature to install in many place (about 10). I'm looking for the cheapest way to connect a DS18B20 instead of a full Atmega168/368 Arduino, I'm looking for another Atmel if possible, a smaller one compatible with Arduino IDE.
Check out the RBBB: buy a 5-pack of bare boards, some pre-programmed ATMegas, and score the parts either from Modern Device or Mouser (you've been lusting after some specialized chips anyway, right? ;)). You'll wind up with 5 Arduinos extremely well-suited for permanently building into projects, for about $12-15 apiece.
You'll also need to buy an interface board to either level-shift the TTL to RS-232, or do USB to TTL serial (also pretty cheap), so you can download sketches to them. But many projects don't need a PC interface for anything other than code changes, so not having the parts cost and board space for one can actually be a big plus.
Some details: I want to have (possibly) a DS18b20 that monitor temperature and turn on/off an heating lamp according to ambient temperature. If temperature cool down to a certain point turn ON the light, if temperature get too hot, turn OFF the lamp. Is simple as that.
But I don't want to have a 40$ device to do that since we can find 5$ one in store. I took that building it should be less expensive, it seem I'm wrong
even if you used a tiny85 your looking at about 3 bucks just for the chip, and you need power regulation, capacitors, something to switch your lamp, a board to mount it on etc (+ shipping)
Be careful with the "just for fun" approach. I have a chicken coop with like $150 worth of electronics in it now due to a "just for fun" project. What did you find for $5? I'd like all of my hardware back from the coop if it's that simple.