This is a project of simple UM3561 loud siren circuit. This simple siren circuit can produce a quite loud sound in an 8 ohms speaker. You can use any speaker from 2 to 5 watt. The circuit can be used as a high power tone generator, alarm, horn or at any place where a very loud siren is required.
The circuit is built around a UM3561 IC, it is an 8 pin dip siren sound generator CMOS IC. It can produce four different siren sounds, which can be selected with switch S1, S2 and S3. The output of the IC is low therefore it cannot directly drive an 8 ohms speaker. Another part of the circuit is an NPN high gain darlington transistor which is used to amplify the output of the IC.The operating voltage of the circuit is 12V. The maximum operating voltage of UM3561 IC is 3.6 volt DC therefore we have used a 3.3V zener diode to step down 12V to 3.3V to smoothly operate the IC. The TIP120 transistor is operated directly with 12V to provide maximum output.
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