Simple Siren using op-amp

Intoduction :-

Device such as burglar alarms and sirens, whose basic purpose is to monitor certain conditions. The above figure shows a simple siren/alarm circuit using a dual-amp MC1458, audio amplifier LM380, and a 1-W speaker. The dual op-amp is used  as a signal generator that produces square, pulse and triangular or sawtooth wave froms.

Operation :-

The A1 and A2 op-amps make up a waveform generator in which the output of A1 is a square wave or pulse waveform and that of A2 is either a triangular or sawtooth waveform. The potentiometer R2 controls the frequency as well as the type of output waveform of op-amps A1 and A2. The switch SW1 connect the output of A1 or A2 to the audio power amplifier LM380, this in turn drives the speaker. Although not used in the circuit of figure 1, a potentiometer may be connected between (+) and (-) inputs of the power amplifier to control its voltage gain, which in turn controls the sound volume. The sound level produced depends on the position of switch SW1, the wiper setting of potentiometer R2, and the value of capacitor C4. Therefore, sound of varying intensities can be obtained by adjusting SW1, R2, and C4.

For higher output power (sound intensities), audio power amplifier may be used in the bridge from. This configuration will also require a higher wattage speaker.

PARTS LISTS :-

R1, R­4 = 10 KΩ
R2 = 20 KΩ potentiometer
R3 = 39 KΩ
C1, C3 =0.1 µF
C2 = 100 µF
C­4 = 0.05 µF
IC1 = MC1458 (dual op-amp)
IC2 = LM380    (audio power amplifier)
8Ω 1-W speaker
SW1 = Three-position switch