Abstract:

The Theft Alarm using IR Sensor circuit is built using a readily available IR sensor, comparator IC LM393, and a relay. The photo diode detects light intensity, while the LM393 comparator processes the signal. When IR beam interruption occurs, the photo diode stops conducting, triggering the alarm. The circuit design minimizes cost and complexity, using common components for reliable operation.

Application of the Circuit:

This Theft Alarm system is designed to detect interruptions in an IR beam, activating an alarm in its absence. Unlike other IR-based circuits, this design uses a simpler and more cost-effective setup, making it ideal for various electronics and automation projects.

Why this Particular Circuit:

The IR sensor and photo diode system ensure easy beam interruption for detection. The circuit operates on a 5V DC supply, which is commonly available, enhancing its usability for various DIY and educational projects.

Explained Working of Circuit:

The Theft Alarm works by detecting IR beam interruptions with a photo diode. The LM393 comparator processes the input from the photo diode, triggering the relay. In the absence of the IR beam, the relay opens, and the alarm sounds. When the beam is present, the system stays inactive.

Testing the Kit:

After assembling the components, connect a 5V DC power source. Hold a hand over the IR sensor to test—when the beam is interrupted, the alarm sounds. Adjust the resistive value of R2 to set the desired detection sensitivity.

Part List:

• Semiconductors: LM393 (IC U1 – 8-pin)
• Resistors: R1 – 100 Ohm, R2 – 10k Ohm (variable), R3 – 1k Ohm, R4 – 1k Ohm, R5 – 10k Ohm, R6 – 10k Ohm
• Capacitors: C1 – 1uF
• Miscellaneous: IR sensor (D4), Photo diode (D3), Red LED (D1), Green LED (D2), 5V USB cable, Buzzer, Relay, PCB.

Key Applications:

Ideal for electronics projects, automation, robotics, and educational purposes. Optimized for performance in India-specific environments.