High Power Siren

admin April 12, 2011 3 Comments

High Power Siren Circuit


This article is all about a comparatively strong siren circuit useful for any purpose.A complementary transistor pair (BC 557 & 337) is arranged as an oscillator, directly drives the speaker.Transistor Q1(BC 557) is used to provide full charging of capacitor C2.When P1 is pressed, C2 discharges through R8 and the circuit starts oscillating at a low frequency that increases slowly until a high frequency steady tone is reached and it is kept.When P2 is released C2 starts discharging and and output frequency slowly decreases.When C2 is charged fully the circuit stops oscillations.


Adjust the values of C2 & R6 to vary the tune.Wire the circuit on a good quality PCB.A good quality common board may also do trick.

Parts List.

R1,R3_________1K  1/4W Resistors
R2,R5_________10K  1/4W Resistors
R4___________220R  1/4W Resistor
R6___________220K  1/4W Resistor
R7___________22K  1/4W Resistor
R8___________100K  1/4W Resistor

C1,C2_________22µF  25V Electrolytic Capacitors
C3___________10nF  63V Polyester or Ceramic Capacitor
C4___________47µF  25V Electrolytic Capacitor

Q1,Q2________BC557   Transistors
Q3__________ BC337   Transistor

SW1________   SPST  Toggle or Slide  Switch

P1__________  SPST  Pushbutton  Switch

SPKR________8 Ohm speaker

B1__________ 12V Battery

Siren Circuit Diagram.

siren circuitWe have more sound and alarm related circuits in our website,take a look below:

1. Police Siren using NE555

2. Canary Chirp Generator

3. Whistle to Beep Circuit

4. Metronome Generator Circuit

5.  Door Bell Circuit

  • Bob Owen
    October 15, 2012

    Hi, I am looking for a high power alarm for my extruder low vacuum alarm. As long as SW1 is lcosed does this alarm repeat until the circuit is re-set?
    Also can i use something different then an 8 ohm speaker?
    What would i need to change to make it a 24 VDC circuit?
    Thanks, Bob

  • Gabor
    July 25, 2011

    Its powerfull, circuit is good 😉

  • DIRK
    June 23, 2011

    high power siren
    wehn pus the button and hold on the bc337 very hot or melting ???

Leave a Reply

Your email address will not be published. Required fields are marked *