Simple Alarm circuit

admin February 23, 2011 1 Comment

Multi Tone Alarm


This is a simple and easy to build multi tone alarm circuit that can be used in burglar alarms or sirens. 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 their power supply is 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.

We have more related Tone Generator Circuits in our website; Take a look:

1. High Power Siren Circuit

2. Melody Generator

3. Tone Generator Circuit

4. Doorbell Circuit

5. Dual Tone Train Sound Generator

  • Faizaan
    September 17, 2013


Leave a Reply

Your email address will not be published. Required fields are marked *