Introduction
We have heard many electronic sounds like a doorbell, phone alarm, and vehicle horn but the sound which makes people scared and worried is the siren of a police van. It would be a little game if we try to make the police siren circuit. The circuit is inexpensive, simple, and easy to make.
The circuit uses two 555 timer ICs, you can also use the NE556 timer IC which has two 555 ICs already built-in inside. Since the police siren is loud so we used a speaker of 64 ohms and 500mW. The two potentiometers used in the circuit are also called preset. The entire circuit drives the power from the 9V battery. This circuit is promising for learner’s practice
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Timer IC | NE555 | 2 |
| 3. | Resistors | 8.2, 8.2K, 10K, 68K | 1, 1, 1, 2 |
| 4. | Capacitors | 10uf, 100uf, 10nf, 100nf | 1, 1, 1, 1 |
| 5. | Diode | 1N4001 | 1 |
| 6. | Speaker | 64ohms/500mW | 1 |
| 7 | Battery | 12V | 1 |
Circuit Diagram Of Police Siren
Working Explanation
The two 555 timer ICs work in a stable mode multivibrator. But, both the ICs have different frequencies. IC 1 works on a slow frequency of about 20Hz with a 50 percent duty cycle, while IC two works as a fast multivibrator with a frequency of around 600Hz. The output of IC1 is given to the control pin5 terminal that produces the siren effect at the output. The pitch can be enhanced through the power amplifier at the output.
Application and Uses
- It is used in police automobiles
- It is used in ambulances
- With some transformation, it can also be used in various sound devices
