<![CDATA[The evolution of Internet of Things (IoT) technology has revolutionized human interaction with the built environment, driving a massive shift toward energy efficiency and comfort through the smart building concept. Artificial lighting systems represent a critical element of building infrastructure that frequently contributes to energy waste. This research aims to design, implement, and rigorously test an IoT-based automatic lighting control system that integrates an ESP32 System-on-Chip (SoC) microcontroller with a Passive Infrared (PIR) sensor, a 5V 2-channel electromechanical relay module, a physical push-button switch, and the cloud-based Blynk interface application. A hybrid system architecture was developed, dividing operational control into two primary modes—manual and automatic—defined in real-time via the Blynk virtual pin communication protocol. In automatic mode, the PIR sensor monitors thermal infrared radiation from human movement to dynamically activate the lights using a software-interrupt (timer-based) algorithm, whereas manual mode maintains local physical control through a hardware pull-up interrupt technique on the push-button switch, alongside remote control via Blynk widgets. Comprehensive testing of the developed firmware demonstrated high reliability with exceptionally low average transmission latency. Furthermore, energy efficiency analysis indicated a potential for significant reductions in electrical power consumption in areas with intermittent occupancy. The implementation of this hybrid system demonstrates that integrating cloud-based digital control need not eliminate local manual control redundancy; instead, it creates a reliable synergy that supports energy sustainability in modern households.]]>
