Indonesia is a tropical country with consistently high temperatures throughout the year. Based on data from 117 BMKG stations, the national average temperature has increased from 26.7°C during 1991–2020 to 27.5°C in 2024. This rise has driven the demand for efficient and user-friendly cooling devices, particularly electric fans as a cost-effective alternative to air conditioners. However, conventional fans still rely on manual operation, which is prone to user negligence, such as forgetting to turn off the device after use. To address this issue, this study designs an automatic fan prototype based on the Internet of Things (IoT), integrated with Google Assistant for manual voice control. The system utilizes a DHT11 temperature sensor and is controlled by an ESP32 microcontroller, while manual control is executed via voice commands through Google Assistant, connected to the Adafruit and IFTTT platforms. The methodology involves reviewing relevant journal literature on prototype design, conducting discussions with academic supervisors, and collecting data through component testing and device trials. The fan is programmed to operate at two speed levels based on room temperature: medium speed at temperatures ≥28°C, maximum speed at ≥33°C, and turns off at ≤28°C. Test results indicate that the automatic fan prototype effectively responds to ambient temperature in degrees Celsius while also receiving manual commands via voice control. In automatic mode, the fan activates at temperatures ≥28°C with a minimum PWM speed of 100 and a
maximum of 225, and deactivates at ≤28°C. In manual mode, the fan disregards temperature readings and operates solely based on given commands. It turns on when the voice command “turn on the fan” is issued via Google Assistant, and turns off with the command “turn off the fan”. Evaluation was conducted through temperature measurement error analysis and the success rate of manual voice command control, demonstrating the system’s accuracy and flexibility in enhancing user comfort and energy efficiency.