I have a design project where i have to design a sprinkler system that takes in inputs and based on those inputs i have different flow rates and duration of the sprinkler. One of the inputs is a temperature sensor, for the sprinklers to turn on it has to be between 70-90 °F. I set up two comparators so that the "-" sides are tied together and each of the "+" sides are set to each of the two temps. Then I have the two outputs of the comparators going into an XOR gate, so I should only get a high when it's between the two temps. The problem I have is the temperature sensor is the LM35CAZ-ND http://www.national.com/ds/LM/LM35.pdf transitor which increases the voltage by 10mV/°C that means the two voltages are .21 V - .32 V for 70 °F - 90 °F respectively, this is too small of a difference so that it's hard to set the two "+" sides of the comparator (LM339). I'm wondering if either someone knows how i could either amplify this difference or set it up so that i get a greater difference between the two voltages. Any help would be awesome as this is my final project and is due Thursday report and all. Thanks