BJT-Based Light Control Switch Using Phototransistor

This project demonstrates the design and implementation of a light-sensitive control switch using a phototransistor and an NPN BJT. The circuit automatically turns an LED ON or OFF depending on the ambient light intensity. When light falls on the phototransistor, it controls the base current of the BJT, allowing the transistor to operate as a switch. The project helps in understanding light-sensing circuits, transistor switching behavior, and basic sensor interfacing. It is a simple and practical application commonly used in automatic lighting systems such as street lights and night lamps.