Figure 1 shows the diagram simple two-tone siren designed to be powered from 12 volt batteries, in particular from a car battery.

It contains three self-oscillators: switching on elements DD1.1, DDI.2 (with a switching frequency of 1 Hz) and two sound ones - on elements DD1.3, DD1.4 (f = 1 kHz) - 1, on elements DD2.2, DD2 .3 (f=500 Hz) - 2. In order for the sound generators to work alternately, control pulses to the second sound generator are supplied from the output of the switching generator through the inverter DD2.1. In this case, while the voltage at the output of element DD1.2 is at a high level, the self-oscillator assembled on elements DD1.3, DD1.4 is excited. When there is a low level at the output of element DD1.2, the self-oscillator, implemented on elements DD2.2, DD2.3, is excited. Pulses from the outputs of sound generators through element DD1.4, which performs a logical addition operation, are fed to an audio amplifier (VT1), the load of which is the dynamic head BA1. Thus, the dynamic head BA1 alternately plays two tones of 500 Hz and 1 kHz for 0.5 s each.

Since the K561LA7 microcircuit has an operating voltage range of 5...15 volts, using resistor R6, by changing the supply voltage of the device, you can adjust the power of the sound signal supplied to the sound-emitting head BA1. The value of this resistor for other voltages (the diagram shows the value of the resistor for the output voltage KREN8A microcircuits– 9 volts) can be calculated using formula 1) in Fig. 1. Although transistor VT1 operates in switch mode, it will still require a radiator, because the power supplied to the emitter BA1, with a supply voltage of more than 10 volts, can greatly exceed 10 W; this power largely depends on the resistance of the emitter. If an emitter with high internal resistance is used as a load, it must be included in the collector circuit of the transistor.

The stabilizer chip is also installed on a small radiator, although with high audio signal powers, the dimensions of the radiators will need to be increased, and the topology of the printed circuit board conductors will need to be adapted, which can be downloaded here along with the diagram.

Be careful when connecting the circuit to the battery. A polarity reversal will inevitably lead to a pestilence of mikrukhs. We used to have a term at work, I apologize - AOD protection - foolproof protection (don’t take it personally), which consisted of: either a series-directly connected diode (calculated for the corresponding current consumption), or a diode connected in parallel to the input power terminals of the device, through fuse. In the first case, useless power will be released on the diode, and in the second, you will have to change the fuse every time you find yourself... JOKE.

A siren is used to produce a powerful and strong sound signal to attract people's attention and is used in fire alarm and automation systems, as well as in combination with alarm devices at various protected sites.

Generators in the diagram are marked with a yellow frame. The first G1 sets the frequency of tone changes, and the second G2 actually sets the tone itself, which smoothly changes on the transistor VT1 connected in series with resistance R2. To select the desired sound, instead of resistances R1, R2, you can use trimming resistors of the same values.

When the power supply is turned on, the sound emitter begins to generate a tonal acoustic signal, the pitch changes from high to low and back. The signal sounds continuously, only the tone of the sound changes, which switches at a frequency of 3-4 Hz.

The siren circuit uses two multivibrators on elements D1.1 and D1.2 of the K561LN2 microcircuit, which controls the tone, and a multivibrator on elements D1.3 and D1.4 of the same microcircuit, generating tonal signals. The pulse frequency generated by the first multivibrator on elements D1.3 and D1.4 depends on elements C2, R2 and C3, R4. You can change the pulse repetition rate, and therefore the tone of the audio signal, using both resistances and capacitors.

Suppose that at the initial moment at the output of the multivibrator there is a logical one level at elements D1.1 and D1.2. Since positive is supplied to the cathodes of diodes VD1 and VD2, the diodes will be locked. Resistors R4 and R5 do not participate in the operation of the circuit and the frequency at the multivibrator output is minimal, a low-tone signal sounds.

As soon as the output of these elements is set to logical zero, the diodes VD1 and VD2 open and connect resistances R4 and R5. As a result, the frequency at the multivibrator output will increase.

The KT815 transistors used in the circuit can be replaced with KT817, and KT814 with KT816. Diodes - KD521, KD522, KD503, KD102.

The following device can be used as a hazard warning light or horn for a mountain bike. It is a two-tone siren and consists of a clock generator on elements DD1.1-DD1.3, two tone generators (the first on elements DD2.1, DD2.2 and the second on elements DD2.3, DD2.4), a matching stage with power amplifier based on element DD1.4 and transistor VT1.

The circuit consists of two generators. The first is used for tone generation, the second for modification and modulation.

For the maximum volume level, it is necessary that the piezoelement receive a frequency equivalent to its resonant frequency via a bridge circuit.

The basis of the design is a powerful multivibrator 4047, operating in an astable mode. All this is controlled by a powerful MOSFET transistor VT1, which is controlled by the NE555 timer, by generating corresponding low frequency rectangular pulses, resulting in a fire siren. Switching operating modes continuously or intermittently is set using a toggle switch.

Pins 10 and 11 of the 4047 microassembly produce antiphase signals from which they control a bridge on four MOSFETs. To obtain maximum volume, that is, set the resonant frequency of the piezoelectric element, a tuning resistance R6 was added to the design.

This circuit is made up of a combination of a musical synthesizer on a UMS-8-08 microcircuit with a powerful output stage of an electronic siren. To start the circuit, a relay is used, the winding of which is galvanically isolated from the rest of the circuit.

The UMS chip has a standard connection diagram. Three push-button switches S1-S3 make it possible to configure the microcircuit to play one of the melodies. When you click on the first button, the melody starts playing, and by clicking on the third you can sort through the melodies and select the one you need.

A selection of several siren circuits on PIC microcontrollers

This circuit is a simple multi-tone siren based on the UM3561 microassembly

The circuit uses an 8 Ohm speaker with a power of 0.5 W. Using two switches, you can select and play different alarm tones. Each position generates its own sound effect.

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Sirens

Sirens, this is an important element of a car alarm. The siren serves to scare away intruders and attract the attention of surrounding people and the owner of the car. Therefore, the volume of the siren is of no small importance; the louder, the greater the psychological impact. Loudness is measured in Decibels; the higher the value, the greater the sound pressure the siren creates. The volume of modern sirens ranges from 90 to 120 decibels. The body shapes vary, but they are all made of durable, heat-resistant plastic and are attached to the car body. can be read here at the end of the article.

Operating voltage of car alarm sirens

12 Volt- for passenger cars and 24 Volt- for freight.

Types of sirens

The siren may look like a regular siren, but if you connect it to 12 volts. then we will not hear a loud click and no other sound. I would like to note that you need to apply voltage only briefly, otherwise it will completely burn out.

These sirens are used in alarms that themselves create (modulate) an audio signal, and the siren is essentially a speaker encased in a siren body and reproduces it. Typically, the wires of these sirens have the same black color and are connected at one end to a permanent positive through a fuse (no matter what), and at the other to the corresponding alarm output.

This control of the siren allows the alarm system to quickly change the volume and tone of the signal. For example: Arming and disarming signals are quiet and pleasant, but during an alarm they are shrill and loud.

Photo of Sirens without internal modulation

Siren with internal signal modulation

This is the most common conventional siren, which is used in the bulk of alarm systems. This siren has two wires for connection: Red +12 Volt is connected to the alarm output, Black -12 Volt is connected to the car body. If you mix up the wires, there will be no sound, but the siren will not burn out, it has protection against such cases.

When voltage is applied, the siren begins to emit the characteristic sound of a car alarm. The siren sound can be different: one-tone (mostly), two-tone, six-tone or any other. It depends on the circuit that is inside the siren.

Some sirens, when the voltage is applied for a short time (setting or disarming), give a reduced sound level, and when the voltage is applied for a longer period (alarm), after 2 seconds they increase it to the maximum possible.

There are sirens with increased power and to avoid failure of the alarm output trigger, connect. This is the case when the car has door control with a key and has a factory alarm, but does not have confirmation signals for arming and disarming, and the owner wants to hear whether the locks worked or not. Sometimes I use it to sound the warning zone of a microwave sensor. Probably many people were annoyed by the constant “blundering” of the car standing under the window, and in order to save the nerves of those around me and still warn the person who came close to the car that the car is under guard, I use a piezo beeper connecting it via .

An electric-air rotary siren is a powerful howler with an electric motor that spins the siren rotor creating a high-speed air flow, which, thanks to the special design of the stator and rotor, is interrupted, creating a powerful, roaring sound.

You cannot connect such a siren directly to the alarm; you need to use a relay. The relay winding is connected at one end to ground, and at the other to the alarm output of the siren, and through the relay contacts we transmit +12V to the positive wire of the rotary siren, the second wire which is connected to -12V (ground) - here is the diagram.

An example is the Electro-air rotary siren PS324 manufacturer Al Khateeb with 12V power supply.

Siren Installation

The requirements for installing a siren are, in theory, quite simple.

1. Install the siren in the smoke space.
2. The siren should be installed as far as possible from the heating elements of the engine.
3. The siren horn should face down to prevent moisture from accumulating inside the siren.
4. The negative wire of the siren can be connected to the body, next to the siren, or to any ground wire, both under the hood and inside the passenger compartment.
5. The positive wire is connected to the alarm output of the siren control. It must have good insulation to avoid rubbing from friction due to vibration during vehicle operation, and also should not sag to avoid getting into the moving parts of the car engine.

In practice, things are not so simple. There may be almost no space, and if there is, then try to fix it there; it is almost impossible to drag the wire through, and so on. But no matter how it happens, you still need to set the siren.

Sometimes you have to drill into the metal bulkhead between the passenger compartment and the engine. If you decide to drill into the bulkhead, make sure that you do not drill through any pipe, cable or anything else. Here the saying “measure twice, test twice and drill once” will be right.

When you screw the siren to the metal body with self-tapping screws, make sure that there is no wire harness passing through this place on the other side of the metal and no block is attached. I had to see drilled blocks and torn wires in the harness.

The ideal installation is when the wiring is disguised as factory wiring, and the siren is hidden and cannot be seen. In this case, an attacker opening the hood will not be able to immediately turn off the siren and this may become a turning point in an attempt to steal a car.

Power siren connection diagram

When the alarm system supplies a positive signal to the siren control wire, relay P1 is activated and closes contacts K1 through which 12 volts are supplied to the siren or several sirens. Using this scheme, you can connect up to 5 or more sirens. You need to connect in parallel - plus to plus, minus to minus. Power supply 12 volts apply to the relay contacts through a fuse from 5A to 20A, depending on the power of the siren or the total power of all sirens.

If you already have a siren and you want to add another one to the cabin or an additional siren under the hood, then you can connect it according to this scheme; you cannot connect it without a relay, this may spoil the alarm output to the siren.

This scheme works if the car blinks the turning lights at the moment of closing and opening the central locking using the original key remote control. If not, then a different circuit is needed.

When the ignition is turned off, there is a negative potential on the ignition wire, sufficient to trigger the relay and even the beeper itself. When the ignition is on, the mini siren will not respond to the opening and closing of the central locking system. The circuit can be simplified by connecting a piezobeeper instead of a relay, observing the polarity (+) to diodes D1-D2, (-) to D3.

For many alarms, along with disarming, the sensors are turned off and this is ideal for this scheme, but there are alarms in which, even after disarming, the sensor remains in working condition and continues to respond to influence, then in this case the connection needs to be changed, otherwise The siren will continue to squeak.

Even the most primitive alarm system has an output for blocking with normally closed contacts. After arming, a negative voltage appears on this wire, and after disarming it disappears. This is the output we use; we connect the negative power supply of the sensor to it, but through the diode with the cathode towards the alarm.

For everything to work correctly, you need to take two diodes, connect them with cathodes together and connect them to our blocking wire. We connect the negative power supply of the sensor to the anode of one diode, and a blocking relay is connected to the anode of the second diode.

Msvmaster - Installing and disabling car security systems.

There are always red and black wires; they are respectively connected to the battery positive and to the vehicle ground. It’s clear with the masses; this was said at the very beginning. The plus is connected to the alarm power wire and as close to the connector as possible. Let me explain why. First, the siren will be protected by a fuse, second, if the alarm harness going under the hood is cut, the autonomous siren will immediately turn on the signal due to loss of power (provided that it was turned on with the key).

There are still two wires left, which raise questions about where to connect them. Please note that when checking the siren, namely when connecting plus and ground, it does not scream, regardless of whether the key is on or not. These two wires are used to make the siren scream. Usually they are labeled "positive trigger" - a positive trigger and "negative trigger" - a negative trigger. One of these wires is connected respectively to the alarm control wire. If in the “Panic” mode a signal (+) appears on the wire, then a positive trigger is used, and if the ground signal is (-), then a negative trigger is used. With this connection of the siren, the main consumption goes through the power wire from the battery, and only low-current control comes from the alarm. And in this case, you can connect an additional simple siren if desired.

Some types of autonomous sirens, of course with a caveat, can be cited as the fact that there are sirens that can scream even with the key turned off when a control signal is given. Others must be turned on with a key.

The advantage of these sirens, as mentioned above, is that after cutting the wires, the siren continues to scream using its own battery. Of course, she screams a little quieter, but this doesn’t make it any easier for the hijacker. And with a good internal battery, it can scream for quite a long time, although at night even five minutes will be enough to perform its function. It is advisable to occasionally check the condition of the internal battery of the siren by disconnecting the terminal of the standard battery or removing the alarm fuse when the siren is turned on with the key, so that this advantage does not turn into a disadvantage.

About the shortcomings. Since there is a key and a lock, it means there must be access to the siren, and at the same time it cannot be hidden far away. The internal batteries of the siren may be destroyed, and the siren will turn into a simple autonomous one, or worse, it will begin to consume increased current, thereby discharging the standard battery.

You can check the serviceability of the siren and the alarm output stage using the method outlined at the end of the article about simple sirens. The only difference is that power must be present on the red wire, and the control signal is supplied to the corresponding input to check the functionality of the siren. All that remains to be added is that there may be a malfunction of the siren lock, which sometimes falls apart or collapses, making it impossible to either turn the siren on or off.

Siren connection diagrams:

To check the functionality of sirens, the conductor with point “A” is the point where the control signal is supplied. The testing method is described in the article about ordinary sirens. A prerequisite is the presence of power and ground on the siren wires.

A) Connecting a siren with positive alarm control. The dotted line shows the possible connection of an additional simple siren.

When replacing an autonomous siren with a simple one, according to the scheme at point “A”, control from the autonomous siren is disconnected, and the simple siren becomes the main one. Insulate the power cable of the autonomous siren.