Temperature-Based Fan Speed Controller

Problem statement

Conventional fans run at a fixed speed unless manually adjusted, which may not match the temperature and wastes power.

Abstract

In this project, a temperature sensor measures room temperature and a microcontroller adjusts the fan speed accordingly using PWM for DC fan or a triac control circuit for AC fan. At low temperature the fan runs slowly, and at higher temperature it speeds up, maintaining comfort while saving energy.

Components required

• Temperature sensor (LM35 / thermistor)
• Microcontroller board (e.g. Arduino Uno)
• MOSFET driver for DC fan or triac driver circuit
• DC fan or small AC fan
• LCD or LEDs for temperature indication
• Power supply
• Supporting passive components

Block diagram

Working

The temperature sensor produces a voltage proportional to temperature. The microcontroller samples this voltage, converts it to degrees Celsius and compares it with setpoints. It then adjusts the duty cycle of a PWM signal (for DC fan) or firing angle of a triac (for AC fan). Higher temperature corresponds to higher fan speed. The current temperature and speed level can be shown on a small display.

Applications

• Smart fans in hostels and classrooms
• Server room cooling control
• Intro to closed-loop control systems
• Automotive or cabinet cooling