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
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.
|1||SEL2||Sound Effect Selection Pin No.2|
|2||Vss||Negative of Power Supply|
|4||NC||Internal Testing Pin : Leave Open for Normal Operations|
|5||Vdd||Positive of Power Supply|
|6||SEL1||Sound Effect Selection Pin No.1|
|7||OSC1||External Oscillator Terminal 1|
|8||OSC2||External 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.
|VDD||NC||Fire Engine Siren|
NC – No Connection
X – Don’t Care
- IC UM3561 – 1
- Resistor 1KΩ – 1
- Resistor 220KΩ – 1
- Transistor BC548 – 1
- Speaker 8Ω, 0.5W – 1
Police Siren Circuit Diagram
Fire Engine Siren Circuit Diagram
Ambulance Siren Circuit Diagram
Machine Gun Sound Circuit Diagram
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.