High power siren circuit using CD40106

If you are looking for a simple siren sound that high power output and very noisy. This may be the best choice for you.

It uses a digital IC, so easy to use CD40106 hex inverter gate.

And four power transistors to increase current out of horn speaker 20 watts, 8 ohms at 12V battery power.

How This Circuit works

In the circuit below. First of all, connects the 12V power supply to the circuit.

High power siren circuit using CD40106

They have two frequency generator circuits.

  • The first part includes  IC1/1 (pin 9,8), R2, C2 to produces the frequency of 1Hz.
  • The second part includes  IC1/2 (pin 13,12), R2 and C3.

Both frequencies are mixed into a modulation signal with  R3, R4, C3, ZD1.

Until there is square wave frequency in changing of two-level frequencies are like common cheap sirens.

It comes out of the second part at pin 12.

Next, It comes to the others pins of IC1 to buffer the signal.  After that, to the power amplifier section.

They include 6 transistors that set in 2 group.

  • First set, Q1, Q4, and Q5
  • The second set, Q2, Q3, and Q6

Both sets will alternately work. To drives the high sound signal to a speaker.

This causes transistor uses low power. But they make high power to output or very loud siren.

Building High power siren circuit

Let’s build them. You should get the components first.

 List Name Detail  Amount 
IC1  CD40106 Hex Schmitt Trigger 1
D1  1N5402  Diode 1
 ZD1  4.7V 0.5W  Zener Diode 1
 C1,C2  1uF 25V  Electrolytic 2
C4  47uF 25V  Electrolytic 1
C3  0.001uF 50V  Ceramic 1
R1  1M  0.25W, 5% Resistors   1
R2  220K  0.25W, 5% Resistors  1
R3, R5  2.2M  0.25W, 5% Resistors  2
R4, R6, R7  100Ω  0.25W, 5% Resistors  3
 Q1, Q2  BC337  0.6A 40V, NPN transistors  2
 Q3, Q4  TIP32  4A 40V, PNP transistors  2
 Q5, Q6  TIP31  4A 40V, NPN transistors  2
 SP1  8Ω , 10W  Horn Speaker  1


This circuit is small in size. So you can assemble them on the perforated board.

You should solder the component onto PCB carefully.

Even IC, transistors, diodes, and the device such as polarized  Electrolytic capacitors, must be correct.

How to use its

This is a super cheap siren is small. It can be applied compatible with various theft protection circuit, decidedly.

For example, to prevent a home burglary, car theft protection, or want to use different alarm sirens.

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This Post Has 4 Comments

  1. hi
    i need some kits with pcb files

  2. Hello,

    I don’t see what are the values for R4 or R6. I also see that R3 and R5 shown twice in the part list.

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