Sound transformer for siren. A simple single-tone siren for notifying important events

The siren is included as standard equipment in security or warning systems. Designed to generate a sound signal in the most sensitive range of the human ear. Thanks to this, the sound of the siren is picked up at a considerable distance from the source.

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Types of sirens for alarms

Sirens are divided according to the following differences:

• the principle of sound generation;
• supply voltage;
• degree of sound pressure;
• type of connection and power supply.

Some of the varieties will be discussed below.

According to the operating principle

The operation of sirens is based on two principles for generating a sound effect:

1. Piezoelectric. Car sirens use the reverse piezoelectric effect, based on the vibration of a piezoceramic plate under the influence of alternating currents. The frequency of the sound is determined by the frequency of the supplied voltage, which ranges from 12 to 20 Volts. A control microcontroller can be introduced into the siren design, which will generate two- or three-tone sound. Car sirens are characterized by the ability to produce various sound signals and melodies, which differ in frequency or discreteness. At industrial enterprises, a voltage of 220 V can be used for sirens of warning systems with a piezoelectric effect. Sound pressure is measured in decibels; for sirens in cars, the range from 75 to 115 dB is used.
2. Electromagnetic. The devices consist of a core of magnetized material on which a coil of copper wire is wound. The core has a cavity inside, with a thin-walled metal partition installed in it - a membrane. When voltage is applied to the coil at a variable frequency (corresponding to the desired sound), the membrane begins to vibrate and produce a single-tone sound with increased volume. To amplify the sound in sirens, an additional generator is used, amplifying the sound with a frequency in the range of 800-2000 Hz. The disadvantage of the design is the energy consumption and the need to use a voltage of 220 V. Today, electromagnetic sirens are rarely used in indoor security systems.

Piezoelectric car siren Electromagnetic street siren

By type of connection and power supply

Sirens can be divided according to the method of communication with the control unit into wired and wireless. The latter receive a signal to operate via a radio channel of various frequencies.

Wired and wireless devices have two power options:

• from the main energy source - a car battery or a standard indoor network;
• with autonomous power supply from its own source (battery or battery).

The making of a talking siren is shown in a video from the Tver Garage channel.

Rework and customization

One way to improve the siren is to change the tone of the sound. This is achieved by transforming the resistance of the resistor on the sound generator controller board. As resistance increases, the sound frequency decreases, and as resistance decreases, it increases. The selection of resistance is carried out experimentally.

To independently manufacture a multi-tone musical siren, you will need knowledge in circuit design and the ability to independently make printed circuit boards. To record melodies into the memory of the generator chip, you will need a programmer (for example, PIC K150). In addition, you will need to buy components in accordance with the diagram.

Assembly sequence:

1. Draw a circuit board diagram in Sprint LayOut.
2. Print the template on polished paper.
3. Apply the template with an iron onto the textolite with a one-sided layer of foil. Before application, it is recommended to clean the surface with 1000 grit sandpaper and degrease it.
4. Remove the paper from the workpiece (by soaking it with hot water).
5. Etch the workpiece in a ferric chloride solution.
6. Drill holes for mounting components.
7. Install the elements in accordance with the diagram.
8. Place the resulting sound generator in the alarm housing.
9. Assemble the housing and install the siren on the car.

Siren circuit based on 561LN2

Siren 12 Volt

A siren with an operating voltage of up to 12 Volts can be built based on two transistors and a speaker with a resistance of 16 Ohms (or a series connection of two 8 Ohm speakers). The device diagram is shown below.

Two-transistor siren

Two tone siren

If desired, the car owner can create a two-tone siren based on multivibrators. When turned on, the sound generator (chips D1.3 and 1.4) creates an acoustic signal, the tone of which periodically changes from low to high (controlled by similar D1.1 and 1.2). The tonality is regulated by the resistances available in the circuit.

Two-tone siren on K561LN2 diagrams

The low tone is adjusted by resistances R2 and R3, and the high tone by R4 and R5. The frequency of tones is set by resistor R1. The parameters of elements C2/R2 and C3/R4 must be identical, since the durations of the positive and negative drops at D1.3 and 1.4 depend on them. When a positive signal appears at outputs D1.1 and 1.2, the diodes VD1 and VD2 close, which cuts off resistances R4 and R5 from the circuit. Due to this, a low-tone signal is generated.

The main element of the siren is the K561LN2 microcircuit

If there is a negative signal at outputs D1.1 and 1.2, then the diodes connect resistances R4 and R5 in parallel with R2 and R3. Due to the change in resistance, the tonality moves to high. Signals of any tone are sent to amplifiers D1.5 and 1.6, and then through the transistor output VT1/2/3/4 to the speaker designated BF1.

Siren with power up to 15 Volts

Based on the UMS-8-08 microcircuit or a similar one, you can build a siren with increased power and switched on using a relay. The siren is capable of operating at voltages up to 15 Volts and is suitable for installation on cars. To turn it on, it is enough to apply a signal to the input of relay P1, for example, in parallel with the circuit of the interior lamp.

Schematic diagram

To configure the microcircuit, use the S1/2/3 buttons (scan through the melodies recorded in the memory). When the relay contacts close, voltage is supplied to the circuit and the sound signal is activated. The UMS-8-08 is powered through the circuit R3 and VD1 (the voltage is stabilized to 3.3 V). The signal from the VT1 collector is supplied to chips D2.2 and 2.3. Moreover, it goes to the first one immediately, and to the second one through an additional inverter D2.1. Due to this, antiphase pulses appear at outputs D2.3 and 2.4, which are supplied to the transistor bridge VT2/3/4/5. When the positive half-cycles on D1 and D2.3 coincide, current flows in one direction through transistors VT3/4 to the speaker. With a negative half-cycle, the direction of the current changes. Due to this, loud sound is achieved. The circuit uses a RES-10 type relay and a quartz resonator for a frequency of 32768 Hz.

Siren based on a cell phone chip

A failed siren can be modified in accordance with the diagram below. It is based on the KA2410 microcircuit from a cell phone call. The signal is amplified by a transistor and sent to the speaker. A protective diode VD1 is installed at the input, protecting the circuit from incorrect connection (supplying negative voltage to the positive input).

Siren based on a cell phone chip

Autonomous siren

An autonomous car siren can operate from a built-in power source or from the main battery. The power type is selected by turning the locking mechanism located on the back of the case. The lock cylinder is connected to contact groups that operate one or another power circuit.

One of the most common autonomous siren models on the Russian market is the Pandora DS-261 with a power of 20 W and a sound pressure threshold of 115 dB. The siren is compatible with all security alarms (Pandora, Starline, Scher-Khan and others) and is sold at a price of up to 500 rubles.

Siren Pandora DS-261 with switching lock

Installation diagram

The DS-261 siren has a wiring harness with four cables for connection, but only three wires are used during the connection process.

Siren connection diagram

Sequence of installation steps:

1. Install the device on the car. It is recommended to install the siren on the engine shield away from the exhaust manifold and ignition system wiring. The installation site must not be flooded with water. When choosing a location, it is necessary to exclude access to the siren from under the car.
2. Lay the connection wires and connect them according to the indicated diagram.
3. Connect the red wire to a constant +12 V power supply from the main source.
4. The black wire is connected to the car body (-12 V).
5. The white conductor receives a positive control signal from the alarm unit. In diagrams, this wire may be designated “positive trigger”.
6. The fourth blue wire (“negative trigger”) is designed to control the siren using a negative signal. It is recommended to cut it off or carefully roll it and place it on the base of the siren.
7. Turn the key to the position with the green dot. In this mode, the siren will automatically go into alarm mode after the power loss from the main battery.

Autonomous sirens from other manufacturers are connected using a similar scheme.

Features of installing autonomous and non-autonomous sirens

Several installation schemes for autonomous and non-autonomous sirens can be used on cars:

1. If a car owner decides to convert the warning system from an autonomous siren to a regular one, then he may be faced with two connection options. When installing a conventional siren instead of a stand-alone one controlled by a positive signal, it is necessary to connect the power of the conventional device to the control wiring. The cable of the autonomous siren cut off at point “A” is insulated. The second wire of a simple siren is output to the body.
2. If an autonomous siren was controlled via a negative wire, then a regular siren is connected using a different circuit. The negative terminal is connected to the negative trigger wire, and the positive terminal is connected to the power wire of the autonomous device.
3. To ensure protection against disconnection of the main alarm key fob connector, it is necessary to upgrade the block. An additional jumper is installed inside the printed circuit board. When the plug is disconnected from the unit, the autonomous siren will turn on and run on its own battery.
4. You can simultaneously use sirens of different types on one alarm system. The non-autonomous alarm device is connected via an additional relay and is protected by a separate fuse. In total, up to five sirens can be installed in parallel connection.

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.

It would seem that to assemble a siren you would need to buy a microcircuit to provide the necessary signal amplification and install a body kit on it. However, to reproduce such a signal with low requirements for sound quality, you can easily get by by assembling a generator using transistors. The diagram is presented below.

Such an assembly provides a fairly loud sound and is quite suitable for a security alarm; naturally, the whole thing works from the on-board network.

The entire element base is common and can be found in any radio equipment store. The circuit is generally not very demanding on the element base; if any element is missing, you can replace it with any one you come across from old trash.

Another advantage of the circuit is that the transistors do not have to be installed on heat sinks; even during prolonged operation they do not overheat.

In the diagram, the dash-dot line shows transistors, indicating two different generators, one serves to set the sound frequency, the other to change it, by selecting different types of transistors. The remaining components, resistors and diodes, I think will not be difficult to find. You can use any old alarm or buzzer as a head.

To increase the power, even from the diagram it is clear that you need to increase the power of the KT817 output transistor. For example, it can be replaced with KT819, however, when increasing the power, it is advisable to install the transistor on the heat sink, otherwise it will not last long.

You need to understand that for signaling it is not at all necessary to fence the low-impedance head, especially since it will heavily load the circuit. Therefore, it is advisable to use simple high-impedance heads (8-16 Ohms).

And I also want to note one point, if anyone has problems with the turbine, that is, it is incorrectly configured or something else, then there is an excellent company that does just that.

A car siren is an additional element of alarm systems, which is designed not so much to protect the car, but to scare away potential car thieves.

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Such devices are simple and self-contained and can reproduce sound, the volume of which varies from 90 to 120 decibels.

General description and characteristics

The main task of a car siren is to reproduce the electrical signal supplied by the security system to its input. The transducer's volume, choppiness, and frequency are controllable characteristics. How effectively and timely the vehicle owner will be notified of the danger directly depends on them.

Types of sirens for alarms

There are several types of devices in question.

• Depending on the location of generation of the emitted signal, sirens are:
• with internal modulation (the nature of the sound is set by a circuit located inside the device);

with external modulation (sound parameters are controlled by the alarm control unit).

• Car sirens also differ in:
• sound generation method;
• sound pressure value;
• mains voltage.

Based on the principle of sound generation

The electrical signal is converted into a sound car siren in several ways:

1. Using a piezoelectric element. The amplitude and frequency of oscillations of the piezoelectric plate are controlled by changing the strength and frequency of the alternating current passed through its circuit. The supply voltage of the element in this case can vary between 12-20 volts. By including a simple programmable microcontroller in the device circuit, the car owner has the opportunity to change the nature of the sound signal at his discretion: from monotonous to two or three tones.
2. Using a rotary electric air device (turbine). Rotating at a given speed, creating and simultaneously interrupting a powerful air flow, its impeller generates sound waves of the required strength and frequency. Due to technical features, it is recommended to connect such sirens to the power supply through a special relay.
3. Inductively. The sound emitter here is a metal membrane. Its oscillations in the field of an electromagnet cause the surrounding air to oscillate according to the parameters specified by the system. Such devices are least in demand in cars due to too high supply voltage and energy consumption.

Piezoelectric siren SAS-81. Filmed by the Shipdip channel.

By type of connection and power supply

Sirens differ in the way they are connected to the main alarm unit: depending on their design, the control signal can be transmitted:

• via connecting electrical wires;
• via radio signal.

For an attacker who wants to neutralize the warning system by interrupting the communication channel between the main unit and the sound emitter, in the second case it will be impossible to do this. A wired connection system does not have this advantage.

According to the method of power supply, sound alarms are divided into:

• autonomous;
• non-autonomous.

Autonomous sirens

Such devices are equipped with an internal voltage source and are only recharged from the main battery. The operating mode (from internal or external battery) is selected by turning the lock, switching the device between the corresponding circuits. It is usually located on the back of the case.

The advantage of such designs is:

• their independence from failures in the on-board electrical network;
• impossibility of disabling them by turning off the power.

1. Large dimensions.
2. The need to constantly monitor the condition of internal batteries. After 2 - 2.5 years, their capacity drops significantly, which entails an acceleration of the discharge of the main battery. Another consequence will be a drop in sound pressure, which for autonomous sirens is already somewhat lower than for those connected to the on-board network.

Autonomous siren

Non-autonomous sirens

Devices of this type are powered by the vehicle's electrical circuit and are capable of generating a sound signal of greater power. They are compact and do not require serious maintenance. However, the stability of their operation is directly related to the condition of the main battery. Damage to the connecting wires completely disables the device, which makes it more vulnerable compared to autonomous type emitters.

Non-autonomous single-tone siren. Filmed by the Unpacking Auto Products channel.

According to the degree of sound pressure

The specified parameter directly determines the volume of sound the siren can generate. The greater the pressure the sound emitter develops, the wider the area its signal covers.

Conventionally, they can be divided into:

• low-power;
• medium power;
• more power.

The selection of a suitable device should be made in accordance with the tasks being solved.

By supply voltage

The siren supply voltage is selected depending on the parameters of the electrical network of the vehicle on which it will be installed.

Signals used in passenger vehicles operate on 12 volts. In alarm systems on freight transport, devices with bipolar power supply of 24 volts are used.

Popular models

The following brands of alarms are in demand on the sound alarm market:

• StarLine;
• Pandora;
• Convoy;
• Cyclon;
• Chameleon et al.

Starline 203

Model features:

• this is a single-tone sound emitter with a very powerful sound;
• the body of such a dynamic siren is made of plastic, insensitive to mechanical loads and high temperatures;
• The Starline shell is impermeable to moisture and dust.

Siren Starline 20.3

Specifications:

• supply voltage: 12 V;
• power: 20 W;
• sound pressure value: 112 dB;
• operating temperature range: -40° + 80° C;
• maximum current consumption: 2 A;
• dimensions: 73x67x69 mm.

The Starline 201 model has the same characteristics. Its body, like the body of the previous device, has the shape of a horn, directed downward when mounted. This position protects the devices from moisture getting inside them.

Pandora DS-261

Features of the Pandora DS-261 model:

• This is a single-tone siren, powered both autonomously and from the vehicle’s on-board network;
• a higher-capacity nickel-cadmium battery built inside it has an increased service life;
• The small dimensions of the device allow it to be placed in the most difficult to penetrate places.

Specifications:

• supply voltage: 12 volts;
• rated current: 1000 mA;
• sound pressure: 115 dB;
• power: 20 Watt.

Falcon AR-165

In offline mode at rated power, the Falcon AR-165 device can operate for up to 30 minutes. A control lock with a high-security key reliably protects the siren from unauthorized hacking.

Siren Falcon AR-165

Specifications:

• rated power: 20 W;
• operating voltage: 12 V;
• current consumption: 1.5 A;
• batteries: GP.

Installing a siren with diagrams and step-by-step instructions

The procedure and features of connecting the device depend on the type of its design, as well as on the type of alarm system with which it is planned to be used.

Regardless of this, there are general rules for installing sirens:

1. Make sure that the installation location is least accessible to intruders.
2. Work is carried out with the negative terminal disconnected from the battery.
3. Before installing the device, you must make sure that there are no heated engine parts near it (ignition system wires, exhaust manifold). Failure to do this will result in overheating and melting of the plastic housing or insulation of electrical connections. The optimal temperature regime of the internal circuitry of the device will be disrupted.
4. The siren is installed in the horn-down position. This prevents moisture accumulated in the engine compartment from entering the device.
5. To connect the negative wire of the device, use any part of the wiring that has contact with the electrical ground of the engine. This could also be a bolt or nut on the car body that has been thoroughly cleaned of rust.
6. Contact of wires with moving or vibrating parts of the body can lead to both chafing of their sheath and damage to the main current-carrying part. This can be avoided by carefully strengthening such places with an additional layer of insulation. Tight, sagging-free laying of wires on the housing will also protect them from mechanical damage.
7. Using self-tapping screws, you should make sure that there are no other important parts of the car structure under the installation site of the sound emitter. These may include wiring elements, plastic or rubber parts.

Installing a siren in a securely protected car engine compartment will provide:

• safety of the device;
• stability of its work;
• inaccessibility to unauthorized persons.

Connecting a self-powered device

Connecting a self-powered device is done step by step as follows:

1. After installing the device, lay the connection wires and connect them in accordance with the diagram.
2. Connect the red wire to a constant +12 V power supply from the main source.
3. Connect the black wire directly to the car body (-12 V).
4. The white conductor receives a positive control signal from the alarm unit. In the diagrams this wire is designated as “positive trigger”.
5. The fourth blue wire (“negative trigger”) is designed to control the siren using a negative signal. It is cut off or carefully rolled up and placed on the base of the siren.
6. Turn the key to the position with the green dot. In this mode, the siren will automatically go into alarm mode after the power loss from the main battery.

Wiring diagram for a self-powered siren

To avoid device failure as a result of a short circuit or current exceeding its rated value for other reasons, a fuse is included in the power circuit. This should not be done if the positive wire of the siren is connected to an already protected positive of the alarm.

How to connect a non-autonomous siren with an alarm system

To connect a non-autonomous siren with an alarm, two standard wires are used: red (in rare cases white) (+) and black (-).

If the device is controlled using positive polarity, the black wire connects to the ground of the vehicle's on-board network. Then the red braided cord is attached to the positive terminal of the alarm.

The second connection option (ground control) consists of connecting the red, positive wire to the battery positive. The circuit is protected by including a fuse in its composition.

Connection diagrams with positive and negative control

Installing a talking siren

With its use it becomes possible to:

• each individual event (activation of a shock sensor, engagement of reverse gear, etc.) is assigned a separate sound, different from others;
• accurately identify the sound of your alarm among others;
• play a music signal from other sources, bypassing the main channel.

Having basic skills and a minimal set of tools, the siren can be connected according to the diagram shown in the photo:

Connecting a talking siren

Reworking and setting up devices

Changing the sound character of a standard car siren at the request of users in some cases requires a complete reconstruction or replacement of its main parts. To do this, you will only need basic knowledge of circuit design, as well as skills in creating printed circuit boards.

You can assemble a circuit of a two- or multi-tone car siren operating on 12 or 15 volts according to the following plan:

1. Create a sketch of a printed circuit board on paper or using a computer program.
2. Using a carbon copy or using a printer, transfer the drawing onto polished paper.
3. Cut out the template.
4. Process the single-sided PCB workpiece using fine-grained sandpaper.
5. After degreasing the surface of the future board using an iron or a homemade device, stick a template on it.
6. Remove it by soaking it in warm water.
7. Etch the textolite plate in a solution consisting of 1 part ferric chloride and 3 parts distilled water.
8. Using a thin drill, drill holes for the legs of the board elements.
9. Solder the radio components according to the diagram.
10. Install the generator inside the siren housing.
11. Install the sounder at the location where it is installed on the vehicle.

Photo gallery

Schematic diagram PCB design

Etched board Track diagram on paper

Placing elements Board in the siren housing

Multi-tone siren

Multi-tone siren - from the variants of the sound annunciator with a changing tone, is assembled on the basis of the 561LN2 microcircuit, with:

1. The operating frequency of generator G2, which is responsible for the sound tone of the siren, is determined by the state of transistor VT1.
2. The parameters of its operation are controlled by adjusting the resistance of the variable resistor R1.
3. The sound generator G1 is responsible for the frequency of the produced signal. Its changes are achieved by adjusting the resistance R2.

To obtain a fixed sound tone, potentiometers R1 - R2 can be replaced with constant resistances with a nominal value of 33 KOhm.

Schematic diagram of a multi-tone siren

Two-tone

A two-tone siren, assembled according to this circuit, is connected to the security alarm input and the volume of the emitted signal is not inferior to industrial designs. At the same time, it consumes significantly less energy and has its own, easily recognizable sound.

The pulses generated at the output of the multivibrator D1.3, D1.4 enter the output stage assembled on the basis of the transistor VT1. By influencing them with a signal with a frequency of 2 Hz, generated by the multivibrator D1.1, D1.2, a two-tone siren sound is achieved.

Two-tone siren circuit

Siren 12 Volt

Using only two transistors and a dynamic head with an induction coil resistance of 16 Ohms (2 x 8 Ohms), they assemble a simple siren circuit with a supply voltage of up to 12 V.

Siren circuit powered by 12V

Siren up to 15 volts

To work in conjunction with a car alarm, a siren assembled using the UMS-8-08 generator is suitable. The increased power of the device requires its connection through a special relay RES-10 (indicated in the diagram as P1).

Siren with supply voltage up to 15 Volts

The microcircuit memory stores 8 melodies, for which buttons are provided for selection:

• S1 (start);
• S2 (stop);
• S3 (selection).

A sound signal at the output of the device is generated when the relay contacts close.

The microcircuit is powered through resistor R3 and diode VD1. Here the voltage drops to 3.3 Volts. The signal from the collector of transistor VT1 through inverter D2.1 goes to the input of microcircuit D2.3. It is directly fed to the D2.2 chip. Due to the phase mismatch of the signals coming from D.2.2 and D.2.3 to bridge VT2/3/4/5, the current in the BA1 speaker circuit flows either in one direction or in the opposite direction. It is amplified due to the coincidence of the positive and negative half-cycles of both signals.

The circuit is powered from a network with a voltage of up to 15V.

Siren based on a cell phone chip

A failed siren can be modified in accordance with the KA2410 microcircuit from a cell phone call.

The signal is amplified by a transistor and sent to the speaker. A protective diode VD1 is installed at the input, protecting the circuit from incorrect connection (supplying negative voltage to the positive input).

Device based on a chip from a mobile phone

How to control a car siren

The car siren is controlled in several ways:

1. An “external” alarm siren can be controlled by a low current negative output. To do this, the Negative Trigger wire is connected to the control output, and the second “trigger” is isolated. It is recommended to connect the second control cord to ground.
2. To control the positive polarity, a cord in white insulation is located inside the siren loop. It must be connected to the output of the main unit. As soon as voltage appears on it, an alarm will sound.
3. A high-frequency radio channel can also be used to transmit the control signal.
4. The operating mode of the autonomous siren is selected by turning the lock located on the rear surface of its body. Depending on the position of the key, the device will work either autonomously or from the vehicle’s on-board network.
5. Non-autonomous sirens are controlled using power wires.

How much does a car siren cost?

Video

Piezoelectric siren. Review, comparison, test. Filmed by the Alarmtrade channel.

The sound siren is used in different places and for a wide variety of purposes to notify about something. It can be adapted to some kind of security system, built into a toy, used as a doorbell, or something else. By assembling this simple one-color siren, we will get a loud and unpleasant sound, just in order to quickly respond to a notification.

A simple siren circuit diagram with a small number of details awaits you in the figure above. Conventionally, the circuit diagram can be divided into two parts: multivibrator - low-frequency amplifier. A multivibrator generates a signal of a certain frequency, and the amplifier, in turn, amplifies it. The result is a loud sound with vibrations of about 2000 Hz.

Our multivibrator generates pulses by quickly opening/closing BC547 transistors. The frequency is mainly related to the capacitance values ​​of the capacitors and partly from the base resistors and the transistors themselves. In the circuit, the standard capacitance C1 and C2 = 10 nF and 22 nF; by varying these values, the tone of the electric siren is also adjusted. You can receive it from the collector of any of the transistors (VT1/VT2). In this device, the signal goes through a resistor further to the ULF stage. The amplifier is based on two very common bipolar transistors BC547 and BD137.

Here are some computational parameters of the multivibrator. The frequency is approximately 959.442 Hz (the multimeter shows 1-1.1 kHz on the collector of the made generator), duty cycle S = 1.45, period T = 0.000104. This information may differ depending on the transistors used, other deviations in the characteristics of radio components... Almost everything affects the sound frequency. The current taken from the circuit's power source can reach up to 0.5 Ampere at 12 Volts.

Circuit and board in Proteus (file ISIS And ARES ): (downloads: 212)
Three-dimensional board in 3DS : (downloads: 127)

The NPN structure transistor from the low-frequency amplifier will heat up when the siren is activated, so we put it on a heat sink; I use a powerful and large C5803.

Now about replacing some parts. Here you can replace a lot of things, for example, we take almost any transistors in the gene (npn) KT315, BC548 and KT3102 - they will all work perfectly. The analogue of BC327 in this circuit will be BC558/BC557/KT3107. BD139 is generally replaced with the same power or more. The capacitance of the capacitors will change the frequency, there is also a lot of choice, experimenting to select the preferred sound. The resistors may change a little, but remember that in the first part of the circuit the resistance of R1 and R4 should be less than R2, R4.

We reproduce the sound of the siren on any speaker that is available, R of the coil is 8-25 Ohms. I tried with a wide variety of both from a radio receiver and from a home landline telephone. Also try testing a piezoelectric element as a sound emitter; be sure to attach a resonator to it (you can use a housing).
Very quiet siren? No problem! We take a ready-made ULF, for example, some kind of tdashka (the digital audio). Their variety is amazing, from small chips in DIP-8 at 1 Watt, to large ones with a power of more than 100 Watts. I would advise taking something average, TDA2003 (up to 10W) ​​or TDA2030 (up to 18 Watt). Don’t forget to look at what kind of power is needed for this or that sound “amplifier”.

Appearance of a mounted mounted siren:

Power supply from 6 to 12 Volts (with a larger one it also works fine). Output power up to five watts. When using rechargeable batteries/batteries, we get an autonomous siren that can operate without mains voltage. If we provide power from 220V, then we take a ready-made power supply or remake the phone charger by replacing the zener diode with the required voltage.

Siren demonstration, video: