Saturday, December 21, 2013

Multi-Tone Siren

This
multi-tone siren is useful for burglar alarms, reverse horns, etc. It
produces five different audio tones and is much more ear-catching than a
single-tone siren. The circuit is built around popular CMOS
oscillator-cum-divider IC 4060 and small audio amplifier LM386. IC 4060
is used as the mult-itone generator. A 100µH inductor is used at the
input of IC 4060. So it oscillates within the range of about 5MHz RF. IC
4060 itself divides RF signals into AF and ultrasonic ranges. Audio
signals of different frequencies are available at pins 1, 2, 3, 13 and
15 of IC 4060 (IC1).


multitone siren circuit schematic

These
multi-frequency signals are mixed and fed to the audio amplifier built
around IC LM386. The output of IC2 is fed to the speaker through
capacitor C9. If you want louder sound, use power amplifier TBA810 or
TDA1010. Only five outputs of IC1 are used here as the other five
outputs (pins 4 through 7 and 14) produce ultrasonic signals, which are
not audible. Assemble the circuit on a general-purpose PCB and enclose
in a suitable cabinet. Regulated 6V-12V (or a battery) can be used to
power the circuit.


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