How to make a sound alarm. We make burglar alarms with our own hands. DIY project: yes or no
This article contains diagrams of the simplest electronic alarms, which can be made by anyone who is at least minimally familiar with electronics or just knows how to hold a soldering iron in his hand. Such alarms will come in handy in many cases. They can be placed on the windows if there is a small child in the house who can open them. There is a guarded parking lot on the doors of an apartment or garage. And when triggered, the watchman will call the police. You can put such an alarm in the apartment if you are friends with your neighbors. Even if you go on a hike, it is not a sin to spread a security loop around the camp at night in case wild animals or strangers appear.
First scheme electronic alarm is simple to the extreme, it couldn't be easier. This is just one transistor, a resistor and an executive relay. If an audible alarm is supposed, then instead of a relay, an audible siren or a howler is turned on.
Principle of operation: The security loop is a thin wire, or closed contact. When the wire is intact (or the contact is closed), the base of the transistor is grounded and the transistor is closed. No current flows between collector and emitter.
If you break the guard wire, or open the contact, the base will be connected to the power source through the resistor R1, the transistor will open and the relay (or siren) will work. It can be turned off only by turning off the power supply or by restoring the security loop.
Such an alarm can be used to guard your belongings, for example. A reed switch is used as a security contact, the alarm is hidden in the side pocket of a bag or backpack, and a magnet is placed next to it. If you remove the magnet from the alarm itself (move the thing), the siren will squeal in all voices.
Second circuit with more advanced custom functions
As in the first case, a security loop, a normally closed (in armed mode) contact or a reed switch closed by a magnetic field serves as a sensor. If the loop is violated, the alarm is triggered and its operation continues until the power is turned off. Loop recovery does not turn off the alarm, it will still continue to work for some time. The alarm has a temporary blocking button, which is necessary for the owner to leave the protected area. The alarm also has a response delay, which is necessary for the owner to turn it off when he enters the protected area.
Let's analyze the operation of the circuit. Before arming the alarm, you must turn off (open) the S1 switch. It must be installed in a secret place near the entrance. You can use, for example, a hidden reed switch, which closes - opens by rearranging an object with a built-in magnet, etc. This switch blocks the operation of the system and it stops responding to a loop break. When leaving, the switch S1 opens and the capacitor C2 begins to charge through the resistor R2. Until the capacitor is charged to a certain value, the system is "blind". And you have time to leave the facility by restoring the security loop or by closing the contacts. By choosing the values of the resistor R2 and the capacitor C2, achieve an acceptable exit delay for yourself.
If the security loop is violated, then capacitor C1 will start charging through the resistor R1. This pair creates a slight delay in the alarm, and the owner has time to neutralize it by turning on the S1 switch. It is necessary to select the values of the resistor and capacitor for a comfortable response delay time.
If the loop is violated by an intruder, who does not know how to turn off the alarm, then some time after the loop is broken, the alarm will be triggered (both inputs of the D1.1 element will be logic "1", respectively, at the output "0". Having passed through the inverter D1 .2 it will again become "1" and open the transistor VT1. The transistor will discharge the capacitor C3 and through the inverter will open the transistor VT2, which will make the executive relay work or turn on the siren.
Even if the attacker quickly restores the loop, the siren will continue to work, since the capacitor C3 will be charged for a sufficient time through the resistor R3. It is the denominations of this pair that determine the operating time of the alarm after the recovery of the loop. If the loop is not restored, the alarm will work continuously.
Microcircuit - K561LA7, transistors - any n-p-n (KT315, KT815, etc.) Power supply - any with a voltage of +5 - +15 Volts. The executive relay or siren can be connected to a more powerful power source than the circuit itself. In standby mode, the circuit consumes practically no current (at the level of self-discharge of the batteries).
Alexei
A dacha, detached outbuildings in the courtyard of a private house can also become an object of encroachments by thieves. It is impractical to install an industrial security system in them, it will cost more than all things stored in such premises.
But it is not worth leaving completely without protection, amateurs to profit at someone else's expense, if they do not take away your property, will harm the structure of the building, the restoration of which will require funds. Therefore, many believe that a simple burglar alarm would be the ideal solution; almost everyone can make it with their own hands.
What is included in such a system?
Typically, such models use an IR motion sensor, a siren and other components for assembling the device. But since wired detectors are designed to operate from a 220 V network, it will have to be upgraded and converted to 12 V. For this, a 6 V relay is added to the circuit. Power is supplied to the sensor through a switch. When the device is triggered, the voltage is applied to the relay coil, it is triggered and leads to the siren being turned on.
If necessary, up to several audio signaling devices can be connected to such a circuit. The presence of a regulator in the sensor allows you to set the time for signaling after the siren is triggered, usually it is no more than 10 seconds. The circuit is turned off using a special device that is switched with a key.
The considered simple burglar alarm is one of the most primitive, it is easy to assemble with your own hands and is economical in terms of energy consumption. For example, no more than 16 alkaline batteries are required for the winter. Such a scheme works in any conditions and is capable of withstanding even negative temperatures, so it is quite suitable for installation in unheated summer cottages.
Types of homemade schemes
Do-it-yourself assembly and installation of the system has several advantages. It saves money, eliminates the possibility of complicity of the employees of the installation company, thieves. But most importantly, in the manufacturing and installation process, you will carefully study the structure of the alarm, you will be able to troubleshoot problems yourself, make adjustments to it by connecting additional sensors and improve your design.
Watching the video, homemade security system:
There are several ways to equip a house with a simple burglar alarm, assembled and installed by yourself. The first and the simplest, but at the same time the most expensive one, is to invite the employees of a special company who will develop the project, select the necessary equipment, install it and perform commissioning. This option is suitable for residential and warehouse premises, but not suitable for summer cottages, since the costs will exceed the value of the property stored there.
Another way is to buy equipment, carefully study the instructions for its installation and operation, and perform the installation yourself. In general, there is nothing impracticable in this approach.
Moreover, many trading companies are engaged in programming the control panel, which will save you from the need to purchase a programmer, learn the rules of working with it and try to complete this stage of work without outside help.
For the simplest type of signaling, it is required to program the device loops, connect them to the general network and write down the required number of keys for access in the memory. They will be required to disarm and arm the object. In addition, the switching on of the light device is programmed, and with a limitation of the operating time of up to 10-20 minutes and a relay output for dialing a mobile phone.
Watching the video, in addition to the basic mobile phone alarm;
On the market, you can find many GSM modules to send a signal to a specified number when the contacts are closed at one of the inputs. These devices are universal and can be connected to any control panel.
If you are already, then they are then connected to the programmed device, which is easy enough for anyone who is able to find the "plus" and "minus" in the circuit. Again, with self-made installation, you will be able to understand in detail the laying of cables and, in the event of a breakdown, fix it without problems.
Watching a video about the purchased GSM system:
For those who are not satisfied with the wired system, you can choose the wireless option. In this case, the installation is even easier, since you only need to hang the sensors in the necessary places and insert batteries into them. The advantage of such systems is the ability to operate on one power source for up to a year, and their cost, when equipped with one or two sensors, is low.
The detectors also have their advantages. They can be transferred from one place to another, if necessary, without much hassle. The above option can be made cheaper by purchasing used equipment. This option is easily assembled with your own hands.
Another, the cheapest, but also ineffective way is the installation of dummies. Such a system is unlikely to be able to scare a hardened thief, but it will be able to stop the boys who decide to fool around in someone else's dacha.
A project for a homemade alarm - is it necessary or not?
Having decided to install a security system in the house, you have to be the first to solve the issue with the development and execution of documentation. A professionally executed project is the basis for a future system, if its installation is carried out by employees of a special company. But what about those who decided to do all the work on their own?
If you install an alarm in a public place, then the project must be mandatory, otherwise the supervisory services will not accept the system. But the house does not belong to such objects, therefore, to install equipment in it, only a sensor circuit is required, which is necessary for future maintenance.
The simplest circuits - on a time relay
We will consider only two of them. The first burglar alarm for the house, which you can assemble with your own hands, is built on a time relay. It has two groups of contacts, one of which works instantly, and the other after 5-10 seconds. This is necessary so that the owner of the object, upon entering it, has time to turn off the system with a special button, which is installed in a hidden place.
Complete shutdown is performed with a special toggle switch. With this design, a position sensor is installed on the door frame. Before entering, a button is installed, which turns the circuit into security mode, after the owner leaves. Typically, such complexes use a 12 or 24 V relay.
Watching the video, in addition to GSM alarm, 12V relay:
The disadvantage of the circuit is the sound of the siren until the alarm is turned off by the button. To eliminate it, the system is supplemented with one more relay, the response time of the contacts in which does not exceed 120-180 sec. After this interval expires, the siren is turned off and remains in this position until the system is armed.
The second of the proposed do-it-yourself kits is based on one relay. The operating time of the siren in it is set using a relay. And it goes into standby mode after the system is de-energized. This circuit uses a thyristor to ensure fire and electrical safety of the equipment.
It is designed to connect a large number of sensors for various purposes. For example, for glass, detectors in the form of metal foil strips can be used, which are triggered when they are broken. Their connection to a common network is performed sequentially.
It is possible to use another type of thyristor. For example, the model PEV-10 with a power of up to 10 W or somewhat with a lower rating.
If the circuit is broken, the relay will trip, which will trigger the siren or any powerful bell. Additionally, a light bulb can be included in the circuit, which is an auxiliary element that does not affect the operation of the system.
Is this method of protection reliable?
Property protection is becoming the most urgent issue in our time. And the way to solve it depends on many factors, but often the cost becomes the decisive one.
It makes no sense to install an alarm, the price of which exceeds the value of the protected property. For such cases, the ideal solution is to design and install the system yourself.
But will such signaling be effective? In some cases, she will certainly be able to scare off thieves, but for reliable protection it is better to use professional equipment and the services of specialists. The use of the console security will not only become reliable protection, but will also allow the return of funds if the robbery is nevertheless committed.
The article provides a diagram of a simple burglar alarm, a description of the work, resident software (firmware). The device is not difficult to assemble with your own hands. All the information required for this is in the article.
General description of the device.
The burglar alarm is assembled on the PIC controller PIC12F629. It is a microcontroller with 8 pins and a price of only $ 0.5. Despite its simplicity and low cost, the device provides control of two standard security alarm loops. The alarm can be used to guard large enough objects. The device is controlled by a remote control with two buttons and one LED.
Our company has moved to a new building. The old burglar alarm system remained from the previous owners. It consisted of an iron box with red LEDs and a siren over the front door, and a smashed electronic unit.
I installed a small board in the alarm box and turned this junk into a modern, reliable burglar alarm. At the moment it is used to guard a two-storey building with a total area of 250 m 2.
So, the alarm provides:
- Control of two standard security loops with measurement of their resistance and digital filtering of signals.
- Remote control (two buttons and one LED):
- alarm activation;
- disabling the alarm through a secret code
- setting a secret code (the code is stored in the internal non-volatile memory of the controller);
- indication of the operating mode by the LED of the remote control.
- The device generates time delays necessary for dialing a secret code, closing the doors of a room, etc.
- When the alarm is triggered, the device turns on the sounder (siren).
- The operating mode of the device is also displayed by an external light source.
The structural diagram of the security alarm looks like this.
Connected to the main burglar alarm unit:
- 2 security loops with
- NC - normally closed sensors;
- NR - normally open sensors;
- Rok - end-of-line resistors.
- External block of sound notification and indication of the mode.
- Backup power supply.
- 12V power supply.
Security alarm loops and sensor connection.
To control sensors (detectors), the device uses standard security loops. Loop resistance is monitored. If the resistance of the circuit is greater than the upper or less than the lower threshold, then an alarm is generated. Normal is the loop resistance equal to the end-of-line resistor (2 kOhm). Thus, if an intruder breaks the wires of the loops or shorts them, then an alarm will be triggered. In this way, you will not be able to disable security sensors.
In this device, the following threshold values of the loop resistance are selected.
Those. loop resistance in the range of 540 ... 5900 Ohm is considered normal. If the resistance value is outside this range, an alarm will be triggered.
Connection diagram of sensors (detectors) to the security loop.
Both normally closed security sensors (NC) and normally open (NO) can be connected to one loop. The main thing is that in the normal state the circuit has a resistance of 2 kΩ, and when any sensor is triggered, it causes an open or short circuit.
To increase the noise immunity of the system, the digital filtering of the loop signals is carried out in the device.
In principle, everything should be clear. Connected to the PIC12F629 microcontroller:
- Two loops through RC chains R1-R6, C1, C2, providing
- formation of loop power supply;
- analog signal filtering;
- matching with the input levels of the inputs of the PIC controller.
To determine the resistance of the loops, a microcontroller comparator is used. An internal voltage reference is connected to the second input of the comparator. The values of the reference voltage source (RV) for comparison with the upper and lower threshold values of resistance are set in software.
- Through RC chains R7-R10, C3, C4, two buttons of the remote control and an LED are connected through a current-limiting resistor R11. The device provides digital filtering of button signals to eliminate bounce and increase noise immunity.
It is worth explaining the purpose of the resistor R17. The GP3 input of the microcontroller has an alternative function - 12 V supply for programming the microcircuit. Therefore, it does not have a protective diode that limits the voltage at the supply voltage level. At a voltage of 12 V at this pin, the microcontroller enters the programming mode. Resistor R17 reduces the voltage at the GP3 input.
- Through two transistor switches VT1, VT2, the microcontroller controls the siren and external LED indication. Because these elements can be connected with a long cable, the transistors are protected from line surges by diodes VD4-VD7. Transistor switches allow switching current up to 2 A.
- The voltage of 5 V to power the PIC controller is generated by the D2 regulator. Don't ignore the VD8 LED. Its functions include not only power indication, but also creating a minimum load for the microcontroller. If the PIC controller consumes less than 2-3 mA current (for example, in the reset mode), then the 12 V voltage through the resistors R8, R10 can raise the microcontroller's supply voltage higher than the allowable one.
- The inputs for the 12 V power supply and the backup power supply are isolated by diodes VD2, VD3. A Schottky diode is used as a VD2 diode in order to provide priority to the power supply in case of equal voltages with the backup power source.
I assembled the device on a 54 x 45 mm board.
Installed it in the body of the old alarm system. I left only the power supply.
The remote control is made in a plastic case with dimensions of 65 x 40 mm.
Software.
The TSR software is developed in assembly language. The program cyclically resets all variables and registers. The program cannot hang.
You can download the firmware for PIC12F629 in HEX format.
Control of the security alarm from the remote control.
The remote control is a small box with two buttons and an LED.
It is better to install it indoors near the front door. With the help of the remote control, the alarm is turned on and off, the secret code is changed.
Modes and management.
At the first power-up, the device goes into SIGNALING OFF mode. The LED is off. The device is in this mode during the working day.
To turn on the alarm (ARMED mode), you must press two buttons at once. The LED will start blinking rapidly, and after 20 seconds the device will enter the ARMED mode, i.e. will start monitoring the status of the sensors. This is the time it takes to leave the room and close the front door.
If during this period of time (20 seconds) you press any button, the device will cancel the security mode and return to the SIGNALING DISABLED mode. Often people remember something just before leaving the building.
In 20 seconds after switching on, the device will enter the ARMED mode. In this mode, the LEDs of the remote control and the external display unit flash approximately once a second. In the ARMED mode, the status of the sensors is monitored.
When any security sensor is triggered, the LEDs start blinking rapidly, and the alarm counts down the time after which the siren will sound. This time (30 seconds) is necessary in order to have time to turn off the alarm by typing the secret code on the buttons on the remote control.
There are 2 buttons on the remote control. Therefore, the code looks like a number of digits 1 and 2. For example, the code 121112 means that you need to sequentially press buttons 1, 2, three times 1 and 2. The code can have from 1 to 8 digits.
If the code is dialed incorrectly or incompletely, you can press two buttons at the same time and repeat the code.
If the code is correctly dialed, the device goes into the SIGNALING OFF mode.
If within 30 seconds after the sensor is triggered, the correct code has not been dialed, then the siren will turn on. You can disable it by typing the correct code. Otherwise, the siren will sound for 33 seconds, and then the device will turn off (switch to SIGNALING OFF mode).
It remains to explain how to set the secret code. This can only be done from the SIGNALING OFF mode.
Keep both buttons pressed for 6 seconds. Release when the remote control LED lights up. This will mean that the device has entered the secret code setting mode.
Then wait until the LED goes out (5 sec). The device will switch to SIGNALING OFF mode, and the new code will be saved in the internal non-volatile memory of the microcontroller.
Because the microcontroller of the device is clocked from an internal generator of low accuracy, then the indicated time parameters may differ by ± 10%.
Security alarm states.
| Mode | condition LED |
Jump condition | Switch to mode |
| SIGNALING DISABLED | Does not light up | Short press of two buttons | Waiting for GUARD (20 sec). |
| Holding two buttons pressed for 6 seconds | Setting the secret code | ||
| Waiting for guards It is necessary to go out and close the front door. |
Flashes quickly | Time 20 sec | SECURITY |
| Pressing any button (cancel) | SIGNALING DISABLED | ||
| SECURITY | Flashes once a second | Sensor triggering | |
| Time to turn off the alarm with a code (30 sec) It is necessary to disable the alarm by dialing a code |
Flashes quickly | Correct code dialed | SIGNALING DISABLED |
| Correct code not dialed within 30 seconds | Siren sound (anxiety) |
||
| Siren sound (alarm) | Flashes quickly | Correct code dialed | SIGNALING DISABLED |
| Time 33 sec | SIGNALING DISABLED | ||
| Setting the secret code | Glows constantly | Code set | SIGNALING DISABLED |
In practice, working with alarms is reduced to actions.
- Leaving the room. Press two buttons simultaneously and close the door within 20 seconds.
- Entering the premises. Dial the secret code within 30 seconds.
Disadvantages, possible improvements.
The device can be easily modified for your own specific conditions. All improvements concern only the hardware part. They do not affect the software.
- It is advisable to install two sirens. One in the outdoor indication and warning unit, the other in a hard-to-reach place. The current of the transistor switch (2 A) allows you to do this.
- It would be necessary to protect the siren wires from a short circuit with a transistor current stabilizer. In the presented version of the scheme, an intruder can short-circuit the siren wires and when the alarm is triggered, a short circuit of the power supply will occur.
- If desired, you can connect powerful and high-voltage sources of light, sound, etc. through electromagnetic relays. The permissible current of the keys allows this, and the keys are protected against emissions when switching the relay winding.
- A battery can be used as a backup power by adding a simple charging circuit to the circuit.
The appearance of the installed alarm system.
Currently, only the front door opening sensor is connected to the device. I plan, over time, to add security sensors. Two loops are enough to guard our two-storey building.
By the way, if only one loop is used, then a 2 kOhm resistor must be connected to the second one.
There are other options for the device software on the site forum. There you can also discuss, ask questions about this project.
The use of autonomous burglar alarms is common. There are many modifications of the wireless system, the equipment of which depends on the conditions of use, the structural features of the area, and the requirements of the owner. The price range is different, the cost-quality ratio is acceptable. At the same time, home-made GSM signaling based on improvised devices is also of interest, especially for those who are familiar with the basics of radio electronics.
GSM alarm system: buy or make yourself?
The answer to the question depends on the requirements, request, presented to the security installation. The variety of functionality and capabilities of wireless systems is wide. Additional equipment is provided by the design feature of this equipment. If desired, needs, it is possible to organize an autonomous scheme that is optimal for a given object. First of all, this concerns the protection of private houses, country cottages, city apartments, garages for cars, etc.
But there are cases when extensive functionality is not needed, it only complicates the use of the device. Here it is recommended to purchase simpler systems with the necessary set of capabilities. It is not recommended to use the cheapest ones due to low efficiency and low reliability.
If there is a desire, as well as knowledge from the field of radio electronics, radio engineering, it is possible to organize GSM signaling on your own. Completion - the most basic tools, simple devices (for example, an old mobile phone, Arduino platform, GSM module, battery, etc.).
For the independent organization of the security alarm, it is better to undertake a specialist who will make the assembly with high quality, with knowledge of many nuances. This model is suitable for installation inside a garage, car, small storage facility. It is recommended to entrust the protection of serious objects (residential buildings, apartments, office premises, shops) to industrial models with remote control, a branched circuit of connected sensors of various directions.
Homemade GSM alarm system from a mobile phone
Often, an independent alarm system is based on a mobile phone. Required set of tools, devices:
- Push-button telephone with speed dialing function (required).
- If desired, listening - headphones with a microphone from a mobile device.
- Soldering iron, related materials.
- Wiring.
- Reed switch, magnet.
- Battery up to 12V (with external power supply of the mobile).
Sequencing:
- Open the telephone set menu, select the “one button” call settings, fix the mobile number (or a group of numbers) to which the DTMF alarm signal will be received, behind the specified button (s).
- Dismantle the phone to the board with the glued film.
- Use a sharp knife to make cuts under the number that was predefined in the menu settings for an emergency call. Lift the film, there is a metal membrane under it, which will subsequently close the contacts (grounding, "patch").
- Solder wires to ground, "patch". To avoid false alarms, it is recommended to use the wires of one loop.
- Cover the membrane to prevent short circuits.
- Install the reed switch on the device, the magnet on the door. To prevent a quick opening of the circuit when the door is closed, a mechanism must be provided to move the magnet to the side.
Options for connecting the resulting device to the alarm:
- Using a relay (normally open contacts).
- Using a biopolar transistor.
- Optocoupler. The most optimal option, creating a galvanic decoupled circuit.
This video describes the diagram in more detail.
How to do it? Option on the Arduino platform
This scheme includes:
- Arduino platform
- GSM modem (SIM900A, SIM800L)
- Power supply, battery.
The system works simply. A connected touch sensor (motion, infrared, etc.), when intrusion indicators are detected, sends a signal to the system, putting it into standby mode. Alarm notification (predefined sms message) is sent to the set mobile number.
A detailed connection diagram is contained in the video
System power supply methods
- From a mobile phone battery. A simple option in which the lithium battery will always be 100% charged. Over time, this will lead to its failure.
- External power supply (battery up to 12 V). It is connected to the phone's power terminals together with its battery. In this case, the charge will be kept at 70%. When the main source of electricity is turned off, the cellular battery will power the security device.
- Without mobile battery (when the device is connected to an alarm with its own power supply).
Benefits. disadvantages
pros homemade security system:
- The lowest cost of initial components in comparison with industrial options.
- Autonomous operation (only periodic recharging of the phone).
- Prompt response.
- Possibility to connect several subscriber numbers.
- Connection options for touch sensors.
- Wireless mounting.
Minuses:
- The system locks easily upon detection. Hidden installation required.
- Local triggering.
- Suppression, signal change.
The use of a hand-made GSM system is justified when it is necessary to install a security device with minimal means, and the significance of the object is not high. For a house, apartment, office, it is best to use industrial security modifications that are more reliable, efficient, and functional diversity.
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Security gsm alarm system for summer cottages
Sometimes it becomes necessary to install a simple and inexpensive burglar alarm. Without unnecessary bells and whistles and "bells and whistles" that manufacturers add to it in order to expand the functionality of their system and somehow distinguish it from other competitors. Summer cottage, garage, household outbuilding or even a greenhouse, in such places it is not always advisable and profitable to install a full-fledged security system.
In this article, we will look at several devices that claim to be simple and accessible to everyone who wants to protect their property from the encroachment of uninvited guests.
What should such an alarm be able to do?
- react to an intrusion (some kind of external influence - movement, the door was opened, hit, etc.);
- give a sound signal to frighten off the intruder;
- be able to arm and disarm;
- it is desirable to consume a little electricity.
This device is intended not so much to close access to the house, but only to scare off the thief. Having heard a loud signal, he will not want to take risks and will not get into the room, in addition to psychological influence, she can also attract the attention of neighbors.
Security alarm based on motion sensor
The simplest burglar alarm for a house can be made by hand on the basis of a conventional household motion sensor for lighting, which are installed in entrances to save energy. But instead of a lighting lamp, you can install a siren.
What is needed for this?
- Motion Sensor- you can buy at any hardware store, for example OBI or Leroy Merlin. It is necessary to pay attention to the voltage of the sensor - we need it to work from a 220V network, the viewing angle depends on the external version of the sensor (wall or ceiling) and the lens used (it can be 180 degrees wide or corridor type). Average cost from 400 to 800 rubles;
- Siren, powered by a 220V network... For example, PKI-3 "Ivolga-220", the average price is 250 rubles. Can be purchased at radio stores;
- Conventional switch, to turn off the alarm. Anyone will do, from 100 rubles. and higher.
The connection diagram is shown below:
The motion sensor should be chosen one that has at least two types of adjustments - time setting (TIME) and sensor sensitivity (SENS). With the help of the first, it will be possible to set the triggering time of our alarm, i.e. siren sounding time. This value is usually set for five minutes. The second adjustment changes the sensitivity of the sensor, for example, if it does not respond to you or to reduce so-called "false alarms".
The switch is needed in order to turn off the device when you are in its field of view and turn it on when you leave this room. It is advisable to install the switch covertly, so that after activating the burglar alarm you do not fall within the range of its action. In addition to the siren, you can also connect a regular light bulb for double impact on the intruder. 
The main disadvantages of this implementation will be that after switching on some models of motion sensors, it takes from 1 to 10 seconds to "stabilize" and switch to standby mode. If you come across such a sensor, you need to add a time relay to the general circuit, which will keep the siren off while it is turned on.
There are also miniature motion sensors on sale that operate on 12V, for example, model DD-03. You can also create a simple alarm on them, but you need to connect it to a 12 volt power source or a battery. Thanks to this, the system will be non-volatile and work even if there is a power outage.
Security alarm from a ready-made kit
The simplest security device based on an autonomous alarm system can work wirelessly. In stores for radio amateurs, you can find two options - based on an infrared sensor (aka motion) or a magnetic contact sensor that reacts to opening. True, the choice is not large enough and often you will have to go shopping to find goods "in stock". Therefore, the easiest way to purchase this product is to order it in one of the major online stores.
Infrared sensor kit.
An example is the Chinese alarm system under the loud name "Alarm mini". Consists of the infrared sensor itself, an installation bracket and one or two key fobs. The kit contains clear instructions for installation and operation. 4 AA AA batteries are purchased separately, but can also be operated with a 6V power adapter (sold separately). It will not be difficult to carry out the installation yourself.
After inserting the batteries into the device, you need to install the unit itself in such a place so that its lens is directed to the protected area. On the front panel there is an infrared receiver window for controlling the alarm from the remotes. A lens that “detects movement” in the monitored area, indicator lights for operation and a siren.
We press the button on the remote control - the green LED lights up, which means that the report has gone to the exit (15-20 seconds) in order to have time to leave the apartment. Then the green peephole goes out - the device starts working. Now, as soon as there is any movement in the room - a person passes, a dog or cat runs, the red LED will light up and after 15-20 seconds a very loud siren will sound. The device is working!
A set based on a magnetic contact sensor.
The burglar alarm based on an opening sensor is a main unit in which there is a sensor with open contacts and a magnet to close these contacts. It is necessary to set them against each other so that there is direct contact between them. If a thief has entered the house, when the door or window is opened, these elements move away from each other and an alarm siren sounds.
Such an alarm can be used mainly to scare off intruders and its main advantage is its low price, about 100 rubles per sensor. And very easy installation, there is adhesive tape on each part, just remove the protective layer and stick the sensor on the front door or window.
Often such kits are used to protect the perimeter of the house at the moment when you are inside, for example, sleeping at night. The sound of the siren will wake you up and you can take any action to protect yourself.
Burglar Alarm Simulator
In urban multi-storey buildings, it is becoming popular to put an apartment on guard, in this case, expensive equipment is bought to protect against intrusion, and the signals are transmitted to the control panel of the security company. But not every owner can afford this, and it is not always justified.
Remember on cars such a device, under the windshield, usually near the steering wheel, there is a red LED that blinks or is constantly on? He warns that the car is under guard. So for an apartment or a summer residence, there are similar structures or, in another way, imitators of the burglar alarm. They are designed to scare off unprepared and unprofessional thieves or burglars.
To make such a simulator, you need to buy a red LED (for example, such an AL307), a back box for placing it, a 100 Ohm resistor, a switch and a compartment for two batteries. For the entire set, you will need to pay about 100 - 200 rubles. Depending on the characteristics of the LED, a current-limiting resistor must be connected to it in series. You will be helped to find the right resistor in a radio store (unless, of course, you have a Soviet AL307 LED, as in our example).
Leaving the house, we turn on the constantly glowing LED, when we return, we turn it off. Strangers will think that the apartment is on an alarm.
