NTC Thermistor Fan Controller

An NTC, an LM358, and a logic-level MOSFET — your first analog thermostat.

Difficulty: Breadboard. Estimated build time: about 40 minutes. Estimated parts cost: about US$3.50. 8-part bill of materials with live supplier pricing. A self-contained thermostatic fan controller that turns a 12 V brushless fan on once a heatsink, enclosure, or any surface it is taped to crosses a temperature you dial in with a single potentiometer.