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Unformatted text preview: CIRCUIT IDEAS ELECTRONICS FOR YOU MARCH 2005 105 W W W . E F Y M A G . C O M S.C. DWIVEDI Y ou can use this simple and reli- able security system as a watch- dog by installing the sensing loops around your building. You have to stretch the loop wires two feet above the ground to sense the unauthorised entry into your premises. Wire loops 1, 2 and 4 are connected to the A, B and C inputs of 7-segment decoder 4511 (IC1), respectively, while the D input of IC1 is grounded perma- nently. The loops are also connected to a dual 3-input NOR gate and inverter CD4000 (IC2) to activate the alarm. Fig. 1 shows the circuit of the digi- tal security system, while Fig. 2 shows the proposed wiring diagram for the loops around the premises. Before us- ing this security system, make sure that loops shown in Fig. 2 are con- PHERDAUS ISLAM nected as shown in Fig. 1. If you dont want to use a buzzer, switch it off by opening switch S2....
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- Spring '09