You can also watch this video on YouTube In this video NTC Thermistor Fan Control Circuit, Fan Speed Control Circuit using NTC Thermistor. I explained how to control dc fan speed using 10K ntc thermistor and a npn transistor br br Indeed Creating an NTC Thermistor Fan Control Circuit is a great way to learn about temperature control and electronicsbr How NTC Thermistor Fan Control Circuit Works:br An NTC Thermistor (Negative Temperature Coefficient) decreases resistance as temperature increases. The thermistor forms a voltage divider with a fixed resistor. As the temperature rises, the voltage at the thermistor decreases. This voltage change controls the base of an NPN Transistor (acting as a switch). When the temperature gets high enough, the transistor turns on, powering the fan. br Components Needed:br NTC Thermistor (10KΩ TTC103 6D3)br NPN Transistor (e.g. 2SC1815, 2N2222 or BC547)br Fan (12V)br Resistors (509 ohms)br Power Supply (12V based on components)br You can use Breadboard & Jumper Wires.