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.
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
Q3__________ BC337 Transistor
SW1________ SPST Toggle or Slide Switch
P1__________ SPST Pushbutton Switch
SPKR________8 Ohm speaker
B1__________ 12V Battery
Siren Circuit Diagram.
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