This one is a simple electronic siren using 555 IC operated in astable mode at around 1400Hz of frequency (see 555 calculator to know how this frequency is obtained). At the start, the capacitor C2 is charged at a rate dependent on the value of C2 and R3. During this charging process, the output frequency of sound in speaker varies until it’s fully charged. Pushing the push button Pb discharges the capacitor C2, thus output sound also changes.
 |
| electronic siren schematic |
 |
| 555 pins CLICK TO ENLARGE |
R1 - 2.2 kilo-ohms 1/4W
R2 - 10 kilo-ohms 1/4W
R3, R4 - 10 kilo-ohms potentiometer
C1 - 47nF (0.047uF) capacitor
C2 - 1000uF/16V electrolytic capacitor
C3 - 2.2uF/16V electrolytic capacitor
Spk - 8 ohms 1/2w speaker
Bat - 6V to 12V battery
Pb - ordinary normally open push button
That wire between R1 and R2 goes into input 7 of the 555 chip just in case anyone was wondering ;)
ReplyDelete