Description
Parts:
This circuit is intended for children fun, and can be installed on
bicycles, battery powered cars and motorcycles, but also on models and
various games and toys. With SW1 positioned as shown in the circuit
diagram, the typical dual-tone sound of Police or Fire-brigade cars is
generated, by the oscillation of IC1A and IC1B gates. With SW1 set to
the other position, the old siren sound increasing in frequency and then
slowly decreasing is reproduced, by pushing on P1 that starts
oscillation in IC1C and IC1D.
The loudspeaker, driven by Q1, should be of reasonable dimensions and
well encased, in order to obtain a more realistic and louder output.
Tone and period of the sound oscillations can be varied by changing the
values of C1, C2, C5, C6 and/or associated resistors. No power switch is
required: leave SW1 in the low position (old-type siren) and the
circuit consumption will be negligible.
Circuit Schematic Diagram- R1 = 470K - 1/4W Resistors
- R2 = 680K - 1/4W Resistor
- R3 = 470K - 1/4W Resistors
- R4 = 82K - 1/4W Resistor
- R5 = 330K - 1/4W Resistor
- R6 = 10K - 1/4W Resistor
- R7 = 33K - 1/4W Resistor
- R8 = 3.3M - 1/4W Resistor
- C1 = 10µF - 25V Electrolytic Capacitors
- C2 = 10nF - 63V Polyester Capacitors
- C3 = 100nF - 63V Polyester Capacitor
- C4 = 100µF - 25V Electrolytic Capacitor
- C5 = 10µF - 25V Electrolytic Capacitors
- C6 = 10nF - 63V Polyester Capacitors
- D1 = 1N4148 - 75V 150mA Diodes
- D2 = 1N4148 - 75V 150mA Diodes
- D3 = 1N4148 - 75V 150mA Diodes
- Q1 = BC337 - 45V 800mA NPN Transistor
- P1 = SPST Pushbutton
- B1 = 6V Battery (4 AA 1.5V Cells in series)
- IC1 = 4093 - Quad 2 input Schmitt NAND Gate IC
- SW1 = DPDT Switch
- SPKR= 8 Ohm Loudspeaker
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