Instructables
The circuit I describe here a simple and cheap sirens of fire engines. The circuit is based on only 2 blocks: one oscillator (slow) and another oscillator (which is faster). Lock the pictures.
This circuit use only 14 components, all of easy acquisition and low price (here in Brazil at least) and can be mounted on a plate trial (which is what I did).
I will tell the story of this circuit. I made a whistle and acute with the 555 ci (which became the second block) and the following thought: if I on the other controlling the second IC 555, have a break in the whistle, thus swinging a whistle. But when you mount the circuit, realized that he played a voltage on pin 5 of IC 2 and change the swing of it! Thus the siren this project!
 
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Step 1: Building and modifying

Picture of building and modifying
The mounting plate in an experimental and easy to do through the scheme. Check all connections for which no errors. If you want a high-power siren, I suggest the following change in Figure 2. It was just that! Build your siren, modify it and improve it and publish your changes! until the next! Bye!
admin5 years ago
This project looks awesome but there isn't enough documentation of you actually making it to be a full Instructable. There are two things which you could do. 1) If you happen to have images of you making your project you can create some more steps, add those additional photos into your Instructable and then republish your Instructable. 2) If you don't have any more pictures of you working on your project, that's ok too. That just means that your project is better suited to be submitted as a slideshow. Your images are already in your library, and you can use the same text that you have already written for your Instructable so it should only take a few minutes to create your slideshow and show the world what you made! Thanks for your submission and let me know if you have any questions along the way.
Nemweb (author) 5 years ago
Of course. but I don't have more photos. Sorry.
J-Five Nemweb1 year ago
I have one question would 3 AA batteries work for this cool project?
Nemweb (author)  J-Five1 year ago
I guess it would work. I don't remind the minimum voltage needed by 555. Take a look at the datasheet to be sure. If you want, you may use TLC555 (the CMOS version of 555), then you can use it with just 2 AA batteries.
J-Five Nemweb1 year ago
At Wikipedia it says between 3 to 15 volts depending on the variation.
Nemweb (author)  J-Five1 year ago
I never had sucess powering a normal 555 with only 3V :c
J-Five Nemweb1 year ago
I was just wondering how to get the 5 volts.
Nemweb (author)  J-Five1 year ago
Use the regulator IC 7805! Simple, cheap and easy!
erikals5 years ago
is that linux you are using or a linux theme for windows?
Nemweb (author)  erikals1 year ago
Yes, it was an old version of Ubuntu (:
Nemweb (author) 5 years ago
Hey! and you like?
JR7375 years ago
A video would be nice too. But I will build this!