Siren Project

Thread Starter


Joined Apr 2, 2009
To make life difficult from the little spare time I got right now I have another headache as of now.
I just got informed on this matter

It seems that the project I did for the police department has been a success.
U see I managed to put light in the regular cycles here.
I think U guys remember, It's how I started to be in this forum.
Thanks to a lot of members.
I manage to make a lot of money. :p

Due to no siren, a cop went flying around 40 feet. Actually the cop at the back seat went, the driver was OK. :eek: A car came out during a chase or something, pretty bad accident. No fault of any one though.

So now I have to make some more flashes, pretty powerful too.
plus a siren have to be built in, a loud one.
Seems a tough job given the intensity of the sound. I have to produce a loud noise from a 4A battery.

So before beginning, I like to know what is the best police siren tone u guys have heard.
I donno what type they use here, seems to me they are multi tone.
I asked them, but what they have are originals, they have no clue.

I just like some suggestions on the best siren used around.
If you can I like to hear them.
I googled but nothing solid came on the type.
I see American and UK but I donno how they sound.

I like to make one sample for them, with the time I have I can't make two or three of them. I have to get parts though.
But I think you guys will know how to make from everyday parts.
If possible throw in some suggestions.
I am googling to find a circuit that would generate tones so I can finalize.

Another Idea is to implement some extra code to the 12F629 that I use to flash the lights.
I like to know is this possible. cause this will make my job pretty easy.

This job is confidential, in some ways.
So please don't post codes or diagrams in this thread, but normal comments are most welcome.
If you are showing a circuit or something give me a heads up. I will PM my private email
why I want no codes or circuits in the thread is that Maldivians have a tendency to steal other peoples work to make a quick buck, not that they can beat me in what I do.
I just don't like complications in these kind of contracts.

Thanks to all.


Joined Apr 25, 2008
Question,can you encase red, white, blue, white leds
In clear hard plastic--arqilic. Have a protected curcuit
board for power and heat. You could make custom
light bars and devises.Like the vertical stem light behind
rider could be 4 color lights.Much brighter light with all the colors.
Guys help me explain that verical light that motor cycles have.
You could go crazy and have leds on uniforms or In all kind of places
that would not be in the officers view.I saw clear roller blade wheels with 4
Last edited:


Joined Mar 24, 2008
New Guy Here - Wanting to build Siren

One of my first projects when I was beginning electronics. It is a howler as opposed to a two tone version, but it is kind of loud..

I'm sure a 555 can do it very well (maybe two). It will be almost impossible to get a decent volume from the batteries you describe though. If you do the current will be substantial.

You'll probably need a transformer for the speaker at such a low voltage to boost the volume.

How about a bull horn with a siren circuit attached?

Thread Starter


Joined Apr 2, 2009
Hey thanks for the Links. I'll check 'em out.
I built the lights before.
But to tell you the truth I wasn't satisfied with it's out put. Since the contractor decided to cut the cost down by reducing LED's.
But now I can do better since there high intensity blue led's. I cannot go for heating ones. I don't have the provision of mounting them on heat sink. I had to cramp them in to the existing signal side lights.
But I think top leds are there that do not generate heat but have a high intensity.

I do have to make new lights for the new batch. But light is not a concern now, since I have done it and I have ways to improve with new leds coming into the market.

I think I will buy them from that led store you suggested. Any idea on small high intensity led's. I prefer 5mm ones.

As Bill said , I too thought of the power drain,this is was the major concern before too and they declined the siren idea, but now it seems I got to find a solution.
The cycles have a provision to add another battery in the compartment.
I know I drove the same type when they were first introduced around 5 years back. I was the first one driving a brand new 125cc auto clutch one. :p No body saw that model before and was everyones attention then.
I still have and being the first one a lot of people want to buy it, but like rest of my stuff, I ain't selling it. :D.

I have added a 12A battery, but I need to be sure about the gear changing sequence to keep the engine rev up so the huge battery will be properly charged. If any one else drives it I had to recharge the battery.

So this option is a no no. since usually cops are pretty stupid when it comes to electronics. ;) ( here that is ).

I think I will need a bull horn and some ways to step up the drive voltage.
I am thinking of adding an extra battery into the compartment and means to charge them at certain intervals since siren won't be used for so long.]

All options are opened.
i.e battery drain testing and horn installation ways.
I have to get a good siren first.

I think I will contact the officer in charge and try to get a recording of the siren.
Till then more suggestions leads to better options.


Joined Apr 25, 2008
Picture the vertical post light with blue light,then with the 4 leds
and brightness and attention, for safety.The white mixed with red,
blue makes a brighter light.


Joined Apr 25, 2008
Knock them off there feet with your new sound that olny you can make,
that cannot be bought on line,with help you can do this, then when people hear the sound ,they hear you.


Joined Mar 24, 2008
Hmmm, You know, you could boost the voltage a lot using more than 4 AA batteries. Since 4 is a typical battery holder why not go multiples, something like 16 AA batteries would be 24V, which should be loud enough for any speaker.

Something like this for higher voltage.

Feed a second 555 oscillator with a resistor divider into pin 5 (using it as a VCO) and you can create a two tone siren.
Last edited:

Thread Starter


Joined Apr 2, 2009
Since we are talking about tones, is it not possible to create them from a PIC.
My first goal is to get the audio ckt as small as possible

Potato Pudding

Joined Jun 11, 2010
For a Siren you traditionally go with a mechanical noisemaker. Basics are a motor run centrifugal squirrel cage fan with the air exhausted through a Venturi to give it higher velocity. Then you have a naturally oscillating reed valve in the air path or you can use a mechanical reed valve also run by the Motor, or a Reed as part of a solenoid/relay that is wired to pulse switch itself so that you don't need an oscillator circuit. You can also see mechanical bellows run with the solenoid that replaces the squirrel cage fan. Not really like a speaker, even though they have some similar features like voice coils. Electromechanical resonators are very loud, with low current draw if they are good.

It is fairly inexpensive to buy a ready made siren. In a quick and dirty situation I would just pick up some car horns from the junk yard. Pulse them on with relays and you will get attention. It will sound just like somebodies car alarm going off. If you could afford to leave them on as long.

To run it from 4 AA batteries is something else, and I don't think it will work but trying full battery current charging a capacitor and then ringing the capacitor discharge through a coil is your best bet. Use that coil spike of power to toot an old car horn. Do that at about 30 Hz 20%DC and you should get attention.

I suggest that the Capacitor be big enough so that each on pulse will be short enough to prevent the capacitor discharging more than a small fraction.

The Capacitor and the Coil should be in boost mode to add their voltages.

To save power you might want to have a another 3 Hz 10%DC oscillator as well and only toot the horn when both oscillators are high.

Look around junkyards for a horn that has a sound you like with low current draw. The mechanical resonator horns are more than you will want to try and recreate. Best idea I can offer.

You might want at least 10 Batteries. 2 batteries for the control circuits. 2parallel x 4 series for the horn power.


Joined Sep 7, 2009
I was wondering of mixing 'em all.. it will be a heck of way to go :p
UK sirens kind of do this. Apparently a normal siren isn't attention getting enough so they alternate between a slow siren, a fast siren and a white noise, which apparently is easier to hear the direction of.

I think it could be done with a PIC and some hard work if you attached a DAC to a whole port or make a DAC like this:
The resistor values should probably be higher.


Thread Starter


Joined Apr 2, 2009
Hey R!ff@ check this out for a quick and dirty way to do it with minimal components >>> might have to "boost" the output to get it to work with a bigger speaker/horn driver.....

B. Morse
I saw that one....still waiting to see a way to do with just one component like a PIC with a DAC.

And mark, that is a summing amp. Right?

I like to know whether it is possible for a PIC to create such tones.
I may not be able to write such complicated code, but I have time to find some one to do it for a price.
I will pay for his time if any one is willing to help me out with a PIC code.

Any one can do using timers and gates, but using a PIC simplifies a lot.
And with a PIC I can put the flash codes too, and also some code to monitor the siren battery voltage, that is charging it and disconnecting it when not needed.

Any one who can do this if not give me an idea which PIC can do this , what I have in mind is a 12F675, or a 16F88, with this all the code can be built and I will have enuf ports to do everything..

My aim is to make it hard for any one to copy my work, as this will happen.
As everyone is looking for something new to copy and cheat.


Joined Mar 24, 2008
American units tend to be howlers, along with a two tone blip to get your attention.

Are you going to include a bull horn feature (you'll already have the amp most likely)? It is another feature cops might like (PULL OVER!).

This is a fun project, I don't have the time I'd like. I'll be following the thread with interest, and probably injecting my 2¢ worth now and then.

Definitely going to need breadboard materials with this one.