Interfacing PIR Sensor with PIC Microcontroller

This security intrusion detection project centers around the PIC16F877A microcontroller, which serves as the central processing unit for monitoring environmental movement. The system is powered by a 12V adapter regulated down to a stable 5V DC using an IC 7805 voltage regulator, supported by 100uF and 10uF filtering capacitors to ensure clean power delivery. The PIC microcontroller requires a reliable clock signal to execute its programmed firmware, which is provided by a 20 MHz crystal oscillator paired with two 33pF capacitors connected to its clock pins. The primary sensing element is a Passive Infrared (PIR) sensor that detects changes in infrared radiation levels caused by human or animal movement within its field of view. When the PIR sensor detects motion, it outputs a digital high signal to an input pin on the PIC16F877A. The microcontroller runs code compiled via the XC8 compiler and flashed onto the chip using a PicKit 3 programmer, managed through the MPLAB X IDE and MPLAB IPE environments. Upon receiving the trigger signal from the PIR sensor, the PIC microcontroller executes its control logic to drive output devices. It activates a buzzer through appropriate current-limiting resistors (such as 680 ohm, 10K, and 560 ohm values) and illuminates an LED to provide both audible and visual alerts. The entire circuit can be prototyped on a breadboard before being soldered permanently onto a perf board using a soldering kit, secured via a 40-Pin IC holder and connected using male and female Bergstick pins and connecting wires.