TMP35/36/37 sensors

The TMP36 (and TMP35 and TMP37) provide a voltage output that is linearly proportional to the temperature in Celsius, which makes them very easy to work with. Connect one to an analog input pin, and the value (between 0 and 1024) read from the pin can be converted to Celcius by this formula:

( ( sensor_value / 1024 * VCC_in_millivolts) - offset_value_in_millivolts ) / scaling_factor

For example, for a TMP36, it would be as follows:

( ( sensor_value / 1024 * 5000) - 500 ) / 10

Which can be simplified as:

( sensor_value * 500 / 1024 ) - 50

Or even:

( sensor_value * 49 - 5026 ) / 100

You can check the math using the reference mV at 25C.