Temperature Controlled Fan using Arduino

The Temperature Controlled Fan using Arduino operates as an automated closed-loop thermal management system centered around an Arduino Uno microcontroller. Ambient room temperature is continuously monitored by the LM35 temperature sensor, an analog sensor that outputs a linear voltage directly proportional to the temperature in degrees Celsius. This analog voltage signal is routed to one of the Arduino Uno's analog input pins, where the internal analog-to-digital converter (ADC) translates the continuous voltage level into a discrete digital value that the microcontroller can process using software logic written in the Arduino IDE. The Arduino evaluates this converted temperature reading against a pre-defined threshold. When the ambient temperature rises above the specified limit, the microcontroller changes the state of a digital output pin connected to the control terminal of a 5V single-channel relay module. The relay acts as an electrically isolated switch: a low-power control signal from the Arduino energizes an internal electromagnetic coil, which mechanically closes a heavy-duty set of contacts. This switching action completes the external circuit required to power the AC fan. Conversely, once the temperature drops back down below the threshold, the Arduino de-energizes the relay, opening the contacts and turning the AC fan off. This continuous cycle of sensing, processing, and switching provides automated climate regulation.