05-12-2012, 02:56 PM
Synopsis On Petrol theft alarm
petrol theft alarm.docx (Size: 2.48 MB / Downloads: 31)
Introduction
Petrol/diesel theft of parked vehicles is quite common. Presented here is an audio-visual anti-petrol theft alarm circuit that can help prevent this crime. The circuit consists of transmitter and receiver sections. The transmitter has to be mounted in the vehicle near the petrol tap, and the receiver in the common room of your house. When someone comes near the petrol tap, you get an audio-visual indication in your room.
The transmitter section (shown in Fig. 1) is built around an infrared LED (IR LED1), photodiode (PD1), comparator IC 741 (IC1), phase-locked loop IC 567 (IC2), 433MHz transmitter (TX1) and a few discrete components. Power supply to the circuit is given by the vehicle’s12VbatterythroughswitchS1.When someone comes near IR LED1, the IR signal reflected off the subject is detected by photo-diode PD1. A voltage difference appears at inverting pin 2 of IC1 and its pin 6 goes high. As a result, npn transistor T1 conducts and enables the PLL 567 to transmit a prefix frequency via transmitter TX1. LED1 glows when a signal is transmitted.The receiver section (shown in Fig. 2) is built around an infrared receiver module (RX1), PLL 567 (IC3), EFY-KnS 8051 development board along with some discrete components.