Temperature-Based Automatic Fan Speed Control Using Embedded Microcontrollers: A Review of Sensing, Pwm Drive and Closed-Loop Control Strategies

Electric fans are used for personal comfort and for cooling equipment such as power supplies, boilers, incubators and ovens. A fan that always runs at full speed wastes energy and produces unnecessary noise, while manual speed selection depends on the user noticing a change in temperature. Automatic fan speed control solves this by measuring temperature and adjusting fan speed continuously. This paper reviews the design of such controllers built around low-cost microcontrollers of the AVR family, such as the ATmega8, ATmega168 and ATmega328 used on Arduino boards. The review covers temperature sensing with the LM35 and alternative sensors, analog-to-digital conversion, pulse width modulation (PWM) drive through a transistor stage, display of set and measured values on a 16×2 LCD, and the power supply. Control strategies ranging from on–off and stepped control to proportional, PID and fuzzy logic control are explained and compared. A reference architecture and control flow are presented for a stand-alone controller using a 12 V, 2 A supply, together with design calculations. Applications in air-conditioning, water heaters, incubators and industrial process equipment, as well as limitations and possible improvements such as wireless monitoring, are discussed.