# Very simple to make it but almost impossible to find the circuit diagram

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#### ilker06

Joined Jun 26, 2018
28
Hi all !

I am new at All About Circuits. To be honest, I am here to find a solution for a problem which is very important for me to solve it.
I finally found a Police Siren circuit which is definetly impressed me with its simplicity, reality and sound quality. Yes I hear you you say " what are you waiting for ? make it. " Unfortunately the only data in my hand is a youtube video and here is the link " https://youtu.be/zfqJ4KA0whw "

I will be appreciated if anyone can give me advices in order to find it and I will be thankful for this. But please do not advice similar circuits because I made almost hundreds and could not have the same sound and specs.

Thanks in advance for all of you.

Regards,
Ilker

#### wayneh

Joined Sep 9, 2010
16,114
Hi all !

I am new at All About Circuits. To be honest, I am here to find a solution for a problem which is very important for me to solve it.
I finally found a Police Siren circuit which is definetly impressed me with its simplicity, reality and sound quality. Yes I hear you you say " what are you waiting for ? make it. " Unfortunately the only data in my hand is a youtube video and here is the link " https://youtu.be/zfqJ4KA0whw "

I will be appreciated if anyone can give me advices in order to find it and I will be thankful for this. But please do not advice similar circuits because I made almost hundreds and could not have the same sound and specs.

Thanks in advance for all of you.

Regards,
Ilker
Pretty tough with no schematic. Could be fake for all we know. Have you tried contacting the author of the video?

#### WBahn

Joined Mar 31, 2012
24,852
You want someone to tell you where to find the exact circuit diagram for some circuit that some guy made at home and posted a YouTube video about?

As already noted, try to contact the video author.

If that does work, back out as much as possible about the circuit from the video. It appears to be a pretty well laid out single-sided board, so you can probably get the majority of it.

I'm guessing the IC is a 555 but it might also be an LM386 or perhaps an opamp. Once you have the bulk of the circuit mapped out, it will be a lot easier to make reasoned guesses about the unknown components.

#### ilker06

Joined Jun 26, 2018
28
Pretty tough with no schematic. Could be fake for all we know. Have you tried contacting the author of the video?
First off all thank you for your effort as writing me.
Nope. I did not try to contact but many people tried and he gave a link on Facebook which is does not exist or it is closed to some people.
He wrote below the video " Sirene polisi dibuat dengan 4 buah transitor, dan untuk audio menggunakan ic LM386 Harga kit Rp. 55.000,- " I guess this is Indian language. I searched for 4 transistors and a LM386 siren circuits on the internet but there is no circuit even a similar one

#### wayneh

Joined Sep 9, 2010
16,114
First off all thank you for your effort as writing me.
Nope. I did not try to contact but many people tried and he gave a link on Facebook which is does not exist or it is closed to some people.
He wrote below the video " Sirene polisi dibuat dengan 4 buah transitor, dan untuk audio menggunakan ic LM386 Harga kit Rp. 55.000,- " I guess this is Indian language. I searched for 4 transistors and a LM386 siren circuits on the internet but there is no circuit even a similar one
Did you search for his kit? Seems he hopes to sell them and that explains why he doesn’t post the details you want. At least we know he used an LM386.

#### ilker06

Joined Jun 26, 2018
28
You want someone to tell you where to find the exact circuit diagram for some circuit that some guy made at home and posted a YouTube video about?

As already noted, try to contact the video author.

If that does work, back out as much as possible about the circuit from the video. It appears to be a pretty well laid out single-sided board, so you can probably get the majority of it.

I'm guessing the IC is a 555 but it might also be an LM386 or perhaps an opamp. Once you have the bulk of the circuit mapped out, it will be a lot easier to make reasoned guesses about the unknown components.
Thank you boss But I am not an engineer and I am just an ordinary hobbyist who can make circuits if there is schematic diagram. Otherwise I can not guess or calculate the components.

#### ScottWang

Joined Aug 23, 2012
6,829
There are components side and solder side of PCB, so maybe you can draw the circuit and then maybe we can try out the details.

He could be used two sets of 2 NPN Transistor Square Wave Oscillator to make the sound and used LM386 to do the amplifying job, I did that kind of circuit long time ago, but I can't guarantee that the sound are the same.

Using a small mic and a amplifier and O'scope then it can be measures the base frequency of sound.

#### Danko

Joined Nov 22, 2017
819
Here is police siren schematic:
POLICE SIREN
Absolutely real sound and loudness...

Last edited:

#### Danko

Joined Nov 22, 2017
819
Agung Supadma said: "Please if you want the message can be wa (WA = Watsap) to nmr 085884939347"
(Silahkan jika mau pesan bisa wa ke nmr 085884939347)

#### ilker06

Joined Jun 26, 2018
28
It is schematic of real police siren!
Edit: From The Signal Division, Federal Signal Corporation (Federal)
Hi Danko,

Appreciated for your effort and your time you wasted for me. I know Federal Signal circuit but it is so complicated.

The circuit in youtube video, the PCB fits inside the man's one hand. So simple and the sound tone and quality is exactly what I want. And seriously I am thinking about Wayneh explanation. What if it is fake video but I watched it several times if any synchronization fail between the sound appearance time and the video frames but everything is OK. In addition, It can cost for him to make a science fiction video for this simple circuit.

Here by I declare that if anyone can find the schematic or create a new one I can pay up to $15.- Dear ScottWang, I don't know If my offer above is suitable for the forum or not. If you warn me to cancel it I will. I beg forgiveness in advance. Thread Starter #### ilker06 Joined Jun 26, 2018 28 Agung Supadma said: "Please if you want the message can be wa (WA = Watsap) to nmr 085884939347" (Silahkan jika mau pesan bisa wa ke nmr 085884939347) Dear Danko, Can't belive my eyes I will try to contact with him. Many thanks . You are great ! #### Bordodynov Joined May 20, 2015 2,418 Before you collect (solder) the device, you can find out how it sounds. This possibility is possessed by LTspice. This allows you to compare sound devices without manufacturing them. #### absf Joined Dec 29, 2010 1,942 From the video, either the PCB or the whole kit costs only 55000 indonesian rupiah, which is about US$3.87 If you can talk him into selling you the kit, it would be cheaper or less trouble to make your own.

But if you want to go the other way, here's what I've done so far. With a little more effort, you can make up the rest of the components or even the resistor values if you're patient enough.

Happy Reverse Engineering.

Allen

#### absf

Joined Dec 29, 2010
1,942
Not sure if the transistors are NPN or PNP, American or Japanese. Orientations on the legs would make a lot of difference.

#### ScottWang

Joined Aug 23, 2012
6,829
Dear ScottWang, I don't know If my offer above is suitable for the forum or not. If you warn me to cancel it I will. I beg forgiveness in advance.
It should be ok until now, if you want to get the same results then you can do as what I suggested or the circuit as the links posted by Dave, I also tested the similar method as that long time ago, but the first stage is a square wave and added a RC circuit, because I wasn't get used to use the output from pin 2 during that time.

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