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Simple Alarm circuit

2015-01-08 02:12  
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Multi Tone Alarm


This is a simple and easy to build multi tonealarm circuitthat can be used in burglar alarms orsirens. The circuit is based on dual op amp MC1458 and? LM 380. The two op amps inside the MC 1458 are used to produce square and triangular waves.LM 380 is used to amplify the output.The first op amp IC1a is wired as an astable multi vibrator and second op amp IC1b is wired as an integrator , to make the square wave triangle.

The two output square ans sine can be selected using switch S1 to the input of IC2 which amplifies it to drive the speaker.POT R4 can be used for tone adjustment.

Simple Alarm Circuit Diagram with Parts List

Alarm Circuit

Alarm Circuit Diagram

Notes .

    IC1a and IC1b are same .So theirpower supplyis common.Wire exactly as shown in figure,nothing to care.C1 and C2 are ceramic, C3 is electrolytic.Pin 6 of IC2 (inv input) has no connection.A dual power supply is needed here.

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