This simple project uses a Dallas DS1820 one wire temperature sensor and a pic 16f628 microprocessor. A simple temperature regulator where a LED symbolizes the Fan.
Data derived from the DS18s20 is a 9bit centigrade temperature measurement. As mentioned the temperature sensor communicates over a one Wire bus that requires only one data line and ground for communication with a central microprocessor.
Read more: DS1820 Temperature regulator using PIC16F628