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Petrol/diesel theft of parked vehicles is quite common. Presented here is an audio- visual antipetrol 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.
7Ke WUDQVPLWWeU VeFWLrQ ( VKrwQ in Fig. 1) is built around an infrared LED (Ir LED1), photodiode (PD1), comparator IC 741 (IC1), phase-locked OrrS ,C 567 (,C2), 4330Hz WUDQVPLWWeU (7X1) DQG D Iew GLVFUeWe FrPSrQeQWV. 3rweU VXSSOy Wr WKe FLUFXLW LV JLYeQ Ey WKe YeKLFOe’V 12V EDWWeUy WKUrXJK VwLWFK 61.
When someone comes near Ir /(D1, WKe ,5 VLJQDO UefleFWeG rII WKe VXEMeFW LV GeWeFWeG Ey SKrWr- GLrGe 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 WUDQVPLW D SUefix IUeTXeQFy YLD WUDQVPLWWeU 7X1. /(D1 JOrwV wKeQ D VLJQDO is transmitted.
7Ke UeFeLYeU VeFWLrQ ( VKrwQ LQ Fig. 2) is built around an infrared receiver module (rX1), PLL 567 (IC3), EFY- KnS 8051 development board DOrQJ wLWK VrPe GLVFUeWe FrPSrQeQWV. ,W rSeUDWeV rII D 9V-12V EDWtery. Alternatively, you can use a 12V DGDSWrU. 6wLWFK 62 LV XVeG Wr SrweU the circuit.
Transmitted frequency from the transmitter is received by the rF receiver module (rX1) and decoded by PLL567 (IC3). The output of IC3 is fed to input port pin P1.1 of EFY-KnS 8051