High Power Siren

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 circuit

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