Over the next two weeks, I'm going to be building a greenhouse fan system. It's not for a real greenhouse, though. It's just for fun. Anyway, my plan is to use the Dragon12+ board that I have, an LM34 temperature sensor, and a little 5V fan.
My goal is to read the temperature, convert it with the A to D converter, calculate the actual temperature from the values in the conversion registers, display it on the onboard LCD, and when the temperature reaches 85F, turn on the fan. Once the temperature gets back down to 80F, the fan would turn back off. So, really, the only temperatures I care about are from about 70-90F (Giving some extra room on both sides of the scale). How could I build a circuit to limit the temperatures that the sensor reads?
Would it be better to just implement it on the software side? My problem is that the A to D converter is 10 bits, so the resolution is (roughly) 5mV (5 volts over 1024 bits), and the sensor increases 10mV/degree. I know that it should be fine in theory, but will such a small step size of the sensor be a problem?