RF based Intruder Alarm

This project extends the functionality of intruder alarm 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.[[wysiwyg_imageupload:191:]]

This project about 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.