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Auto-guard with a changeable sound pattern of the alarm signal. 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 electronic security device works in conjunction with both contact (door) sensors and body rocking sensor. In addition, it provides the ability to change the nature of the sound ("sound pattern") of the alarm.

In the described autoguard, CMOS microcircuits are used, which provide high power efficiency. The watchman also has a number of operational amenities not found in other similar devices. The transition of the guard to the armed mode occurs when the driver's door is closed (and not after some time has elapsed), the characteristic sound is inherent in the alarm signal. The autoguard has an LED indicator of the operating mode and a switch for the sound mode of the signal. In continuous mode, the signal sounds until the power is turned off, and in short mode, it sounds for a limited time. When you try again to open the doors or rock the car in short-term mode, the signal sounds twice as long, on the third attempt - six times longer.

The device allows, within certain limits, to delay the operation of the sound signal when the driver's door is opened. All timing relationships are determined by the parameters of the timing circuit of one generator.

The main technical characteristics of the device:

  • Time to switch to security mode, s.......18
  • Alarm triggering delay time (when opening the driver's door or closing the swing sensor), s.......6
  • Signal sounding time: at the first attempt, s.......24
  • at the second attempt, with ....... 48
  • at the third attempt, from ....... 44
  • Sound pattern.......short-long-short; the short one is twice as long as the long one.
  • Signal series repetition interval, s.......7,5
  • Current consumed in security mode, no more than, mA.......3
  • Dimensions of the guard, mm....... 50x45

The schematic diagram of the autoguard is shown in fig. one.

Auto-guard with changeable alarm sound pattern
Fig.1 (click to enlarge)

On fig. 2 shows the connection diagram of the autoguard to the sensors and elements of the electrical circuit of the car.

Auto-guard with changeable alarm sound pattern

In Fig. 2, SB1 is the driver's door switch (in parallel to which a rocking sensor can be connected), SB2 - SBn - switches for other doors, hood and trunk lid, SA1 - power on toggle switch, SВ2 - operation mode selection switch, EL1 - ceiling lamp, HL1 - watchdog LED indicator, K1 - car horn relay.

When the power is turned on (both with the driver's door open and closed), a short positive pulse generated by the differentiating circuit C2, R3 sets the trigger DD2.1 and the counter DD4.2 to zero. A high level from the inverse output of the trigger DD2.1 through the diode VD2 is fed to the input R of the trigger DD2.2 and sets it to zero. Similarly, a high level from the inverse output of the trigger DD2.2 sets the counter DD4.1 to zero. A low level from the direct output of the trigger DD2.1 disables the operation of the clock generator assembled on the elements DD3.2, DD3.3. LED HL1 glows continuously, indicating the supply of power to the guard.

When the driver's door is closed, a positive drop from the output of the element DD1.1 is fed to the clock input C of the trigger DD2.1 and switches it to a single state, since its input D is a log level. "1". A high level from the direct output of the trigger DD2.1 allows the generator to work, the HL1 LED starts blinking, signaling the transition of the guard to the armed mode. In this mode, the current consumed from the on-board network is about 3 mA and is mainly used to turn on the HL1 LED.

If you now open the driver's door, the trigger DD2.2 will switch to a single state and a low level from its inverse output will allow the counter DD4.1 to work. turn off after 1 s, a high level will appear at the output 4 of the DD1.3 counter, which will open the DD2 element through the DD6 element. The signal from the output of the adder DD8 is fed to the current switch, assembled on transistors VT4.1 - VT1.4 and controlling the activation of the horn relay K3.4. When the relay is triggered, an alarm will sound with a specific "pattern": short-long-short. The duration of a short signal is half the length of a long one. Such series of signals are repeated with an interval of 1.3 s.

If the door is closed, then with the SA2 switch open - short-term mode, after 24 s, i.e. at the end of two series of alarms, a high level will appear at the output 2 of the counter DD4.2. This positive voltage drop through the VD4 diode is fed to the differentiating circuit C5, R5, which generates a positive pulse. This pulse trigger DD2.2 switches to its original state, and autoguard goes into protection mode.

A second attempt to open the door will cause an alarm to sound after 6 seconds, but since the counter DD4.2 is not set to zero, a high level at its output 2 will appear only after 48 seconds. The duration of the signal will be twice as long (Fig. 3). At the third attempt to open the car door, a positive drop at the junction point of diodes VD3 and VD4 will appear only after 144 s and 12 series of alarms will sound. On subsequent attempts, the alarm signal will be repeated from four, then from twelve series.

Auto-guard with changeable alarm sound pattern

When the contacts of the switch SA2 are closed (long mode), the diodes VD3 and VD4 are closed permanently and a series of signals sound until the watchman is turned off.

If you open any other door (except the driver's door), hood or trunk lid in armed mode, the contacts of one of the buttons SB2 -SBn will be closed. A high level from the output of the inverter DD3.1 will switch the trigger DD2.2 and enable the counter DD4.1. The signal generated at the output of the adder DD1.3 will pass through the element DD3.4, since its second input through the element DD1.4 receives a high level from the output of the inverter DD3.1. The alarm will turn on almost instantly. If the open door, hood or trunk lid is then closed, then the further behavior of the guard will be the same as when opening and closing the driver's door.

The guard is assembled on a double-sided printed circuit board made of foil fiberglass 50x45 mm in size. The drawing of the board is shown in Fig.4. When mounting parts on the board, be careful - some points must be soldered on both sides of it.

Auto-guard with changeable alarm sound pattern

The device used resistors of the MLT-0,125 type, capacitor C3 of the KM6 type, the rest - KM5. Diodes can be used any low-power silicon, suitable in size, for example, from the KD503, KD509, KD510 series. KD521, KD522. Transistors VT1, VT2 - low-power silicon, can be replaced by KT312. KT342, KT3102. transistor VT3 - on KT313, KT326, KT3107. Instead of KT814B, any transistor pn-p structure of medium or high power from the KT626, KT818, KT816, KT837 series is suitable. Zener diode VD5 - any for a voltage of 18 - 30 V. Instead, it is permissible to turn on a medium power diode, for example, the D226, KD! 05 series, by connecting it in parallel with the winding of the K1 horn relay.

An auto-guard assembled from serviceable parts does not require adjustment. The time intervals of the tripod signal can be adjusted by changing the resistance of the resistor R4. The SA1 switch must be installed in a hidden place in the vehicle interior, and the HL1 LED must be installed in front of the windshield so that the light signals are visible from the outside. The pendulum motion sensor of the car body can be connected in parallel with the SB1 contacts, however, at the moment of closing the driver's door, due to body vibration, an alarm may sound prematurely. To exclude this phenomenon, the autoguard should be supplemented with a time delay circuit of the trigger GSh2.2 (Fig. 5). The printed circuit board provides for the possibility of installing these additional elements. In the absence of a swing sensor, jumpers are installed instead of resistor R11 and capacitor C6. At the indicated ratings, the time delay for the autoguard to switch to armed mode after closing the driver's door is approximately 18 s, which is quite enough to calm the sensor.

Auto-guard with changeable alarm sound pattern

Consider two options for constructing a simple remote rocking sensor. Figures 6 and 7 show the design options for these sensors, which differ from each other only in the location of the contacts. The first sensor has a fixed contact, which is made in the form of a cone, while the second one has the same contact ~ movable.

Auto-guard with changeable alarm sound pattern

Auto-guard with changeable alarm sound pattern

Consider the design of sensors. In the sensor, the movable contact is fixed on the base 6, which is an insulating material (getinaks, a piece of plywood). A spring 5 is attached to the base with two screws. The stiffness of the spring is selected such that in a calm state, a metal ball 4 fixed on it (Fig. 6) or a metal funnel 3 (Fig. 7) does not deviate to the side under the influence of its mass.

When the base 6 is tilted by approximately 5°-10°, the ball or metal cone, under the influence of its mass, should fall on its side and touch the second fixed contact 1. The sensitivity of the sensor can be adjusted within small limits by changing the distance between the movable and fixed contacts by, for example, moving the rod vertically in the threaded connection 2 by turning the knob 1. When the knob is turned in one direction, the distance between the contacts increases, in the other it decreases. Accordingly, the sensitivity of the sensor to operation also changes. By selecting the sensitivity of the sensor in such a way, it is not difficult to ensure that it operates at a well-defined given angle of inclination of the base 6.

Bracket 8 can be made of any metal. A threaded hole 2 is made in its upper part, for example, for a bolt 1 with a diameter of MB. At the base of the sensor is a flat magnet 7, which allows you to easily place the sensor on a horizontal surface of the car body, for example, on a gas tank.

With correctly selected spring stiffness and the gap between the contacts, even a slight swaying of the car leads to the sensor being triggered. However, one should not strive for the maximum sensitivity of the sensor, because even with a slight wind, it will work and disturb others.

See other articles Section Automobile. Security devices and alarms.

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