This project describes a circuit for a siren. IC 555 is used so that the circuit components are low cost and available off the shelf. Two 555 ics are used. One of them is modulating frequency oscillator the other is modulated frequency oscillator. Note the connection between the two ICs. Instead of the rectifier and the filtered power supply, you can use a 9V battery.
This produces low frequency. With this frequency, the high frequency oscillator is modulated. The components are selected such that,
- Its frequency is 0.577 Hz.
- Duty cycle is 0.6.
- Period is 1.732 sec.
The oscillator oscillates with,
- 577 Hz
- Duty cycle is 0.6 and
- Period is 0.00173 sec.
8 ohm speaker with paper cone (nearly 4 cm diameter) is used.
|7||resistors||5k,10k (0.25W)||2 each|
|10||speaker||8 Ohm, 4cm dia||1|
|11||pcb||General purpose, 4″ X 4″||1|
|13||battery||9V, flat,non rechargeable||1|
Note: You can eliminate the rectifier (diodes) and filter (1000mfd capacitor) components from the above list if you use a 9V flat battery.
This project is available in the kit form. Contact Omkar to buy it. This site has no commercial connection with his activities.