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Car alarm. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms

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The proposed car alarm device (AC) performs almost all the necessary functions, does not contain scarce parts and can compete with industrial systems.

The UAS is powered by the car's on-board network (+12 V), and if it fails, it continues to function normally, since it has an internal source. UAS scheme is shown in Fig.1. (45 Kb)

Each correct connection of the electronic key to socket X1 is accompanied by a short start of the siren and flashing of the vehicle's parking lights, as well as by the alternating transition of the UAS from the "Security" mode to the "Disabled" mode.

Off mode

In this mode, the device consumes a completely negligible current, and all electrical equipment of the car operates in normal mode. The UAS sensors are disabled and the LED is off.

Security mode

The consumed current does not exceed 5 mA. All sensors are activated, the LED flashes at a frequency of 1,4 Hz, the ignition and engine start system of the car is blocked.

UAS goes to "Alarm" mode, if one of the sensors is triggered. In this case, the siren instantly turns on, the side lights start flashing (f=1,6 Hz), and an attempt to start the engine fails. The consumed current does not exceed 2 A in this mode. The UAS will remain in the "Alarm" mode for another 20 s, provided that all sensors have returned to their original state. If not, the twenty second cycle will be repeated until the sensors return to their original position. It is possible to transfer the UAS to the "Off" mode from any state only with an electronic key.

The UAS scheme contains:
- DA1, R1...R4, C1, PA1 - position sensor, made on the basis of a microammeter. It provides arming at any initial position of the body;
- DD1, R6...R13 - receiving part of the electronic key;
- R10'...R13'-remote electronic key. Logic "1" at pin 10 DD1 appears only when the following conditions are met:
This is the "highlight" of the whole scheme. For simplicity, it is convenient to take the value of all resistors R10...R13 and R10'...R13' equal to 10 kOhm.
- VD1...VD4 - protection elements of the circuit when 1 V is applied to X220. In this case, they will simply burn out without damaging the rest of the circuit elements;
- SB - contact contactors. They are installed on the doors, hood, trunk. The sensor closes when trying to hack;
- DD2.1, C3, R5-single vibrator, providing suppression of interference from the electronic key for the normal operation of the counting trigger DD3.1;
- DD2.3, R16, R19, R20, C6, VT1. VD8 - time delay elements (20 s) in the "Alarm" mode;
- DD2.4, R17, C4, VD10 - elements of a single vibrator - a shaper of the siren start pulse at each UAS transition to a new mode;
- DD4.4, R18, R21, C5 - pulse generator (f = 1,6 Hz), control LED VD11;
- DD4.1...DD4.3, С7...С10, R22...R28, VT3...VT6 - electronic siren;
- DD4.1, VT2, K1. K1.1 - control elements of the "dimensions" of the car (P = 1,6 Hz);
-K2,K2.1,VT7,VD14, R29 - elements for blocking the ignition system and starting the engine;
- GB1, VD15, VD16, R30 - uninterruptible power supply and charging elements. The charge current GB30 depends on the value of the resistance of the resistor R1;
-VD13, C11 ... C13, DA2 - power filter and stabilizer +9 V.

The initial reset of the circuit is due to the fast charge of C2 through R14. In this case, DD3.1 at pin 4 and DD3.2 at pin 10 through DD2.3 are reset to zero states. UAS is set to the "Protection" mode, and all sensors are activated. Logic "0" from output 13 DD3.2 disables the operation of the siren and "dimensions". Logic "1" at pin 2 of DD3.1 allows the generator to work on DD4.4 (F=1,4 Hz), which periodically turns on VD11, and also provides an opening voltage based on VT7. To ensure efficiency, relay K2 is only activated when an attempt is made to start the engine.

As soon as one of the SB sensors is triggered, the UAS instantly switches to the "Alarm" mode. This is due to the appearance of a logical "1" at pin 8 DD3.2 through DD2.2. Trigger DD3.2 switches to a single state and starts the siren DD4.1...DD4.3. Contacts K1.1 begin to close at a frequency of 1,6 Hz, providing flashing side lights. LED VD11 continues to flash, and the engine remains blocked. At the same time, C6 begins to charge through R20. As soon as it is charged (20 s), the logical "1" through VD8, DD2.3 enters the base VT1 and pin 10 DD3.2. If the sensors have not returned to their original state, then VT1 discharges C6, and the 20-second cycle repeats again. If the sensors nevertheless returned to their original state, the trigger DD6 is reset along with the C3.2 discharge. UAS again switches to the "Protection" mode.

You can turn off the UAS instantly only with an electronic key. Each correct connection of the key to X1 causes the appearance of a logical "1" at pin 10 DD1.1 and a logical "0" at pin 11 DD2.1. This leads to switching the counting trigger DD3.1 to the opposite state. Logic "1" from pin 1 DD3.1 through VD7, DD2.3 gets to pin 10 DD3.2, resets it and holds it in the zero state, i.e. UAS is in "Off" mode. Logic "0" from pin 2 DD3.1 extinguishes VD11 and unlocks the engine ignition system.

Reconnection of the electronic key puts the UAS back into the "Protection" mode. Each UAS transition to a new mode is accompanied by a short start of the siren (0,7) s and a flashing of the dimensions. This is ensured by a fast charge or discharge of C4 through R17 and the operation of the elements DD2.4, VD10.

Details and construction

Emitter VA1 - any dynamic head for 10 W (8 Ohm) or 20 W (4 Ohm). VT2...VT7 - any of the KT972, KT973, KT853, KT829 series. Transistors VT3 ... VT6 are installed on one common radiator through mica gaskets. A VD16 diode is also attached here. VT1 - any of the KT315, KT3102, KT503 series. VD1...VD4 - any low-voltage diodes with a reverse voltage of 10...20 V. VD5...VD10 - any of the series KD521, KD522, KD503, KD510. VD12 ... VD14 - any of the series D226, D7 and others for a current of at least 0,1 A. VD15 ... VD16 can be replaced by KD2997, KD2999 and others for a current of at least 10 A. R30 - MLT-1, the rest resistors - MLT-0,125 or MLT-0,25. GB1 - any small battery, preferably without liquid electrolyte. It is installed outside the speaker cabinet. X1 - any five-pin connector. It is installed in the rear-view mirror of the driver or in any other place, but outside the car. VD11 - red LED AL307 or similar. It is installed under the front windshield^ so that it can be clearly seen from the street. K1, K2, K2' - any relays for a switching current of at least 5 A. Moreover, the contacts K1.1 must be normally open and connected in parallel to the switch "dimensions" of the car, and K2.1, K2.G - normally closed and connected to the gap wires from the ignition switch to the ignition coil and from the ignition switch to the starter relay, respectively. Relays K2 and K2' can be replaced by one with two pairs of contacts.

The printed circuit board is shown in Figure 2 (37 Kb) and shown in detail. All conductors are shown through the board, which is one-sided and contains 10 jumpers. All conductors through which a large current flows are made as wide as possible and soldered with solder. The ground bus is also soldered.

Setting. As a rule, the device starts immediately. Sometimes it is required to select the resistors of the electronic key. To do this, by applying the supply voltage to the circuit, by selecting R13 they achieve the appearance of a logical "1" at the output of the element DD1.4. Similarly - for R12, achieving the appearance of a logical "1" at the output of DD1.3, etc. Resistor R4 sets the required sensitivity of the body position sensor, but this is done when the UAS is already installed on the car.

Author: A. Chastov; Publication: N. Bolshakov,

See other articles Section Automobile. Security devices and alarms.

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