he LM35 of National Semiconductors that is used in this project is a precision centigrade temperature sensor in a TO92 package. It has an analog output voltage with a range of -55ºC to +150ºC and a accuracy of ±0.5ºC . It operates from 4 to 30 volts, so it is ideal for using with a micrcontroller.

lm335 4

lm35 2

The output voltage is 10mV/ºC . The output voltage is converted by the AD convertor of the ATMega328. The temperature is shown on a terminal display. In this example the thermometer has a range of 0ºC to 40ºC and a resolution of 0.5ºC. If you want to have a readout in Fahrenheit you can use the LM34.