RF based Intruder Alarm

The functionality of intruder alarm can be extended to alert a user at a distant location. The intrusion can be detected at a faraway place by making use of RF communication. For this purpose, an RF module can be used as has been explained here. This module transfers the interruption signal, wirelessly, from the IR sensor to a speaker or buzzer.

This intruder alarm circuit can be divided into three parts, namely, IR circuit, transceiver part and the output. The IR circuit is used as a sensor to detect an intrusion in its proximity. RF module works as the transceiver here. For more details, refer wireless RF remote. The transceiver transmits the signal generated by IR sensor. It provides this signal to the data pin of decoder IC. The output part consists of a NOT gate IC 74LS04 (to invert the low signal) and a buzzer to alert the user.

 

Initially when there is no activity, the output of IR circuit is high. When a person comes within the range of IR sensor, the output of circuit becomes low. The output of IR is given on the data pin of encoder IC HT12E which is active low. HT12E encodes this signal into serial form after which it is transmitted by the transmitter.

 

The serial data is received by a receiver placed at some other place. The signal is then given to the data pin of decoder HT12D to obtain the original signal. On reception of signal, data pin becomes low and this low signal is given to 74LS04, which inverts it. The high signal goes to the buzzer connected to 74LS04. This way whenever an intrusion takes place, the sensor detects the IR pulse and eventually the buzzer produces sound.

More than one IR sensors can also be installed at different locations and can be interfaced to RF module as has been explained.

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IR LED | Infrared LED

 

An IR LED, also known as IR transmitter, is a special purpose LED that transmits infrared rays in the range of 760 nm wavelength. Such LEDs are usually made of gallium arsenid...

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Piezo Buzzer

 

The piezo buzzer produces sound based on reverse of the piezoelectric effect. The generation of pressure variation or strain by the application of electric potential across a piezoelectric material is the underlying principle....

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IC 74LS04

7404 is a NOT gate IC. It consists of six inverters which perform logical invert action. The output of an inverter is the complement of its input logic state, i.e., when input is high its output is low and vice versa.

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HT12D

HT12D is a decoder integrated circuit that belongs to 2¹² series of decoders. This series of decoders are mainly used for remote control system applications, like burglar alarm, car door controller, security system etc. It is mainly provided to interface RF and infrared circuits.  They are paired with 2¹² series of encoders. The chosen...

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HT12E

HT12E is an encoder integrated circuit of 2¹² series of encoders. They are paired with 2¹² series of decoders for use in remote control system applications. It is mainly used in interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have same number of addresses and...

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RF Module

The RF module, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF syst...