Mohamed Ayman Abdelfatah

Home Security System with Motion Detection

This project is a motion-activated alarm system that utilizes a PIR (Passive Infrared) sensor to detect movement and trigger an alert. It integrates several key electronic components to ensure stable and reliable operation: 🔹 PIR Motion Sensor – Detects human motion through infrared radiation. 🔹 NPN Transistor – Functions as an electronic switch to control the relay. 🔹 Base Resistor – Limits current to the transistor’s base to ensure proper operation and protection. 🔹 Relay Module – Controls high-power loads such as the alarm buzzer. 🔹 Capacitor – Stabilizes the signal and reduces electrical noise and false triggers. 🔹 Buzzer (Alarm) – Emits an audible alarm when motion is detected. 🔹 Transformer + Voltage Regulator – Converts AC voltage and regulates it to a stable 5V DC for powering the entire circuit. Working Principle: When the PIR sensor detects motion, it sends a signal through the base resistor to the NPN transistor. The transistor switches on and activates the relay, which in turn powers the buzzer. The capacitor filters out noise, ensuring stable performance. The entire system is powered by a regulated 5V DC supply derived from a transformer and voltage regulator. PCB Design and Fabrication: The circuit was fully designed using KiCad, a professional PCB design tool. After the schematic was finalized and the PCB layout was created, the board was etched (chemical etching process), drilled, and all components were soldered manually to complete the hardware assembly. This project is a practical example of applying embedded electronics in security systems, smart automation, and sensor-based alert systems.