Siren Generator using IC UM3561

Siren Generator using IC UM3561

IC UM3561 is a CMOS LSI IC commonly used in alarm and toy applications. It is able to generate Police Siren, Ambulance Siren, Fire Engine Siren and Machine Gun Sound just by changing simple connections. It is a low cost and low power IC which can work down to 2.4V. We need only a few additional components as this Integrate Circuits has built in oscillator and selector circuits.

 About IC UM3561

IC UM3561 - Block Diagram

IC UM3561 – Block Diagram

Basic blocks of IC UM3561 are shown in the above block diagram. There is an OSCILLATOR CIRCUIT, which generates the necessary clock for the operation of the IC. The frequency of the oscillation is determined by the resistor connected to OSC1 (PIN : 7) and OSC2 (PIN : 8) of the IC. A 220KΩ resistor connected across these pins will provide satisfactory results.

Pin Diagram

UM3561 Pin Out

UM3561 Pin Out

 Pin Description

Pin No.SymbolDescription
1SEL2Sound Effect Selection Pin No.2
2VssNegative of Power Supply
3OUTPUTMono-tone Output
4NCInternal Testing Pin : Leave Open for Normal Operations
5VddPositive of Power Supply
6SEL1Sound Effect Selection Pin No.1
7OSC1External Oscillator Terminal 1
8OSC2External Oscillator Terminal 2

There is a tone generator, which is able to generate different tones using the oscillator clock and according to the data given by the ROM. Each data stored in the ROM corresponds to each tone and it can be selected by using the address of the data location. Address of the tone is provided by the ADDRESS COUNTER section of the IC.

I already said that this IC can generate 4 different sirens. These 4 sirens require 4 different sequence of tone generation, that means 4 different sequence of address counting. The address counting sequence is determined by the CONTROL CIRCUIT and SELECTOR blocks of the IC. We can select 1 of 4 sirens using SEL1 (PIN : 7) and SEL2 (PIN : 1) of the IC.


SEL1SEL2Sound Effect
NCNCPolice Siren
VDDNCFire Engine Siren
VSSNCAmbulance Siren
XVDDMachine Gun

NC – No Connection
X – Don’t Care

Components Required

  • IC UM3561 – 1
  • Resistor 1KΩ – 1
  • Resistor 220KΩ – 1
  • Transistor BC548 – 1
  • Speaker 8Ω, 0.5W – 1

Police Siren Circuit Diagram

Police Siren using IC UM3561

Police Siren using IC UM3561

 Fire Engine Siren Circuit Diagram

Fire Engine Siren usingIC UM3561

Fire Engine Siren usingIC UM3561

 Ambulance Siren Circuit Diagram

Ambulance Siren usingIC UM3561

Ambulance Siren usingIC UM3561

 Machine Gun Sound Circuit Diagram

Machine Gun Sound IC UM3561

Machine Gun Sound IC UM3561

The siren signal generated by the IC is available at PIN 3. As these signals are very weak to drive a speaker, we need an amplifier. Here BC548 transistor is used as an amplifier.

Want to see the Output ?

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Comments (9)

  • joel

    is 5v input voltage acceptable?

    September 18, 2014 at 6:41 am
  • Ligo George

    No, continuous supply of 5V may damage the IC, you should use a 3.3V zener with a series 100 ohm resistor for reducing the supply given to IC UM3561

    September 18, 2014 at 11:38 am
  • Tommmmy

    Hi Ligo, Is it possible to implement Image Processing in VLSI?

    September 19, 2014 at 12:23 pm
  • joel

    is this method ok to generate atleast 3v?

    5v input votlage then 1n4001(2pcs series connection) then connected to UM3561 pin 5…

    October 4, 2014 at 9:45 pm
  • Ligo George

    Yes, it is fine..

    October 6, 2014 at 10:03 pm
  • lokesh

    whats the specs of loud speaker used??

    June 22, 2015 at 1:49 pm
  • lokesh

    i cant get the output ..

    June 23, 2015 at 11:11 am
  • Ligo George

    You can use a small speaker for that, eg : 8 ohm, 5w

    July 1, 2015 at 7:06 pm
  • Ligo George

    Above circuit is 100% working, as shown in the video.

    July 1, 2015 at 7:08 pm

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