# A Simple and Cheap Fireman Car Siren.

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## Introduction: A Simple and Cheap Fireman Car Siren.

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!

## Step 1: 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!

## Recommendations

• ### 3D CAM and CNC Class

599 Enrolled

• ### Planter Challenge

We have a be nice policy.

## Questions

And Oh yes it runs on 12 volts from a variable power supply.

I made a simpler version of this were I put two darl transistors in parallel with a 555 timer and got a high pitch siren sound. 1 K ohm R1, R2 470 K ohm, Capacitor = 1 uf.

Of course. but I don't have more photos. Sorry.

6 replies

I have one question would 3 AA batteries work for this cool project?

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.

At Wikipedia it says between 3 to 15 volts depending on the variation.

I never had sucess powering a normal 555 with only 3V :c

I was just wondering how to get the 5 volts.

Use the regulator IC 7805! Simple, cheap and easy!

is that linux you are using or a linux theme for windows?