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    UM3561 is an excellent ROM IC that can generate Multi siren tones simulating Police siren, Ambulance siren, Fire brigade siren and Machine gun sound. This 8 pin low power IC can work down to 2.4 volts.

    The UM 3561 is a low cost siren generator designed for use in toy applications. The IC has an inbuilt oscillator and tone selection pins. It is easy to make a siren generator with only a few external components. Only one external resistor and a speaker driver transistor are sufficient to make a simple siren generator.

    Inside the UM3561

    Inside the IC, there is an oscillator circuit and the frequency of oscillations is controlled by the external resistor connected to OSC 1(Pin 7) and OSC2 (Pin 8). A 220 K resistor will give satisfactory results. The oscillations thus generated will be then transferred to a control circuit which function based on the tone selection through the connections of SEL 1 (Pin 6) and SEL2 (Pin 1) . The control circuit passes the signal to an address counter and then to the ROM. The tone pulses thus generated will be available from the output pin 3. Since the sound is weak, an amplifier is necessary to get loud sound. A single NPN transistor will amplify the sound.

    Pin Assignment

    Pin 1 Tone Sel.2
    Pin 2 Gnd
    Pin 3 Output
    Pin 4 NC- Used for testing purpose
    Pin 5 +3V
    Pin 6 Tone Sel .1
    Pin 7 Osc 1
    Pin 8 Osc 2

    Tone Selection

    By changing the pin connections of Sel.1 (Pin6) and Sel. 2(Pin 1) it is easy to change the siren tones.
    Sel 1Sel 2Tone
    Pin 6 Pin 1

    NC NC Police siren
    +3V NC Fire Engine sound
    Gnd NC Ambulance Siren
    NC +3V Machine Gun sound

    UM3651 Siren Generator Circuit Diagram

    Absolute Maximum ratings
    Supply voltage Min. 2.4VTyp 3V Max 3.5V
    Operating current Min – -180 uA

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    12 Responses to "UM3561 Siren Generator Design"

    1. very good website
      thank you

    2. i need more about sound generetor desine

    3. see electronics for u for more no circuits.for this ic usage visit 312 circuit

    4. The above circuit has an error. It should have resistor between the speaker/battery and the zener diode/100u/pin 5.
      As it stands it will probably destroy the chip and the zener diode as there is no current limiter between the battery and the diode.

    5. sir, i wanna to sensor projects.

    6. RASHMI SHRIVASTAVA says: on April 8, 2012 at 10:47 pm

      too gud……… really helpfull… thanx for d infrmtn…..:)(

    7. Dont you think a resistor is needed before the zener?

    8. i need information about the IC’s used in Fire /burglar alarm

    9. NIKHITA Mahendra DHANAWADE says: on March 7, 2014 at 4:21 am

      This information is really Nice. And in easy language….. Thanks

    10. what is the replacement for UM3561? i need the answer right now.please..thank you\

    11. shanthini devi says: on April 29, 2014 at 7:20 pm

      why 220 k is used?

    12. what is the loud speaker’s impedance??
      is it 8ohm??

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