Police siren using NE555

Description.

A lot of electronic circuits using NE555 timer IC are already published here and this is just another one.Here is the circuit diagram of a police siren based on NE55 timer IC. The circuit uses two NE555 timers ICs and each of them are wired as astable multivibrators.The circuit can be powered from anything between 6 to 15V DC and is fairly loud.By connecting an additional power amplifier at the output you can further increase the loudness.

IC1 is wired as a slow astable multivibrator operating at around 20Hz @ 50% duty cycle and IC2 is wired as fast astable multivibrator operating at around 600Hz.The output of first astable mutivibrator is connected to the control voltage input (pin5) of IC2. This makes the output of IC2 modulated by the output frequency of IC1, giving a siren effect. In simple words, the output frequency of IC2 is controlled by the output of IC1.

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Circuit diagram.

police-siren-using-NE555

Notes.

  • The circuit can be assembled on a Perf board.
  • I used 12V DC for powering the circuit.
  • Instead of using two NE55 timer ICs, you can also use a single NE556 timer.
  • NE556 is nothing but two NE555 ICs in one package.
  • Refer the datasheets of NE555 and NE556 to have a clear idea.
  • Speaker can be a 64ohm, 500mW one.
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12 Responses to “Police siren using NE555”

  • Stephen says:

    is it ok if i just connect the output to a microphone connector and plug it in an amplifier for a loud speaker, instead of using a small speaker? or do i have to make another circuit for it? please help. thanks!

  • abumbe francis says:

    Please,I am an electrical power and machines student, can anybody tell me which of the site to find power and machines project topics.

  • elvis says:

    Where is the negative terminal of battery connected

  • faseeh janjua says:

    how can I build a horror sound….???
    plz…tell me…??

  • arc_reactor says:

    i have experimented with this circuit and i get three different tones. from the very low frequency signal of the ic1 output from the pin 3 i planted different amounts of resistor with a corresponding amount of electrolytic cap. i get an ambulance-like tone using a 22k resistor tapped with the positive pole of a 1000uf cap. negative is on the ground. the signal is then fed to the pin5 of ic2 to produce a frequency modulated signal. this is then amplified to produce an even louder output. i can get a fire truck-like sound with different values. try it. its pretty fun.’;.,’ thanks

  • RICK says:

    This seems like a FUN Circuit to Build,,,,Groovy!!! I Like 555 Timer Circuits,,,Can We Have Some More Of Them???

  • Hans Elfelt says:

    I’m after the deep growling police horns used when police cars are stuck in the traffic.
    They are used extremely often by Russian traffic-police.

  • seetharaman says:

    Hi Edgardo
    Make RVFM / UK Thro Rapid Electronics
    Diameter 66mm
    Frequency Response 350Hz to 4.5kHz
    Height 20mm
    Impedance 64R
    Maximum Power 600mW
    Type Mylar Speaker
    This is a standard speaker used in games console. If not available you can use minimum 2 nos 8 ohms speakers in series as load.

  • Edgardo says:

    Hi, Can I use an 8 ohm 0.5 watt speaker for this circuit?, I can not find a spaker of the 64 ohm value.
    Thanks.

  • riddick says:

    Modern emergency lighting is installed in virtually every commercial and high occupancy residential building. The lights consist of one or more incandescent bulbs or one or more clusters of high-intensity light-emitting diodes (LED). The emergency lighting heads are usually either PAR 36 sealed beams or wedge base lamps. All units have some sort of a reflector to focus and intensify the light they produce

  • M.K. Ansari says:

    i am getting same e mail with same subject twice in a day.it is irritating. try stop repeated mail