Here is an inexpensive electronic siren circuit built around the most popular and low-cost IC 741. The circuit is basically a square wave generator that is used here to produce the tone of a siren.
Circuit Description of Electronic Siren Circuit using OP-Amp 741
The IC1 is used as a low-frequency multivibrator, the output of which modulates the high-frequency tone produced by the IC2 multivibrator. The final output is amplified and converted into a loud siren by transistor T1 and the speaker.
Various interesting tones can be obtained by changing the values of capacitors C1 and C2 and resistors R2 and R6. If the value of C1 is increased, the siren will produce sounds like that of a fire engine.
Check out other various different sound generator posted on bestengineeringprojects.com
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PARTS LIST OF ELECTRONICS SIREN CIRCUIT USING OP-AMP 741
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Resistor (all ¼-watt, ± 5% Carbon) |
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R1 = 10 KΩ R2 = 1 MΩ R3 – R9 = 100K R10 = 1 KΩ |
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Capacitors |
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C1, C2 = 0.01 µF (Ceramic Disc) C3 = 0.001 µF (Ceramic Disc) |
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Semiconductors |
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IC1, IC2 = 741 (General Purpose Operation Amplifier) T1 = 2N1481 (Silicon Bipolar Power Transistor) |
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Miscellaneous |
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Output transformer LS1 = 4Ω loudspeaker |
what value is the ouput transformer?
The transformer should be able to drive a 4-ohm loudspeaker.