Multiple alarm circuits are developed and are distributed in the market so as to serve the needs and demands of client. Though the design parameter may vary, but all circuits are based on the same principle to provide security services under probable conditions. Designing these circuits becomes entertaining with different sound effects we can use during the designing phase. A similar electronic siren/alarm circuit is depicted in the figure below. The electronic siren circuit is different from other siren circuits from a fact that it uses 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 saw tooth wave forms.
Circuit Description of Electronic Siren Circuit:-
Talking about the working of the circuit, op-amps IC (IC1 consist two op-amp) form 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 saw tooth waveform.
The frequency as well as the type of output waveform of op-amps A1 and A2 is controlled by the potentiometer R2. In this circuit, the switch SW1 is used to connect the output of A1 or A2 to the audio power amplifier LM380, which in turn drives the speaker. As per need, we can also insert a potentiometer between (+) and (-) inputs of the power amplifier to control its voltage gain, which in turn controls the sound volume. Depending on the position of switch SW1, the wiper setting of potentiometer R2, and the value of capacitor C4, the level of sound desired from the circuit is determined. For this reason, by adjusting values of SW1, R2, and C4, we can obtain the desired level of sound intensities from this circuit.
One must set up audio power amplifier in the bridge form to obtain higher power output or greater sound intensity. A higher wattage speaker is required for this purpose.
PARTS LISTS OF ELECTRONIC SIREN CIRCUIT
Resistors (all ¼-watt, ± 5% Carbon)
R1, R 4 = 10 KΩ
R2 = 20 KΩ potentiometer
R3 = 39 KΩ
C1, C3 =0.1 µF
C2 = 100 µF
C 4 = 0.05 µF
IC1 = MC1458 dual op-amp
IC2 = LM380 audio power amplifier
8Ω 1-W speaker
SW1 = Three-position switch