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Autoguard on one chip. 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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A simple car security device is made on a K561LN2 microcircuit with a low current consumption (80 μA in armed mode) and allows you to connect a large number of sensors and control the moment the car ignition is turned on.

According to its characteristics, the car security device is close to the one described above, but contains several additional elements that can significantly expand its functionality.

The main technical characteristics of the guard:

  • Time to switch to armed mode, s .............................................. .. 40-50
  • Alarm delay time, s ....................... 7
  • Duration of sounding of an alarm signal, with....................... 40 - 60
  • Frequency of alarm interruptions, Hz............................................... 1
  • Current consumption in armed mode, not more than, µA ....................... 80
  • Dimensions of the guard with a swing sensor, mm .......................... 70x115

The circuit diagram of the autoguard is shown in Fig.1.

Autoguard on one chip
Fig.1 (click to enlarge)

The security device works as follows. Before leaving the car, the driver turns on the supply of the watchman with the SA1 toggle switch (according to the diagram, position 1), installed in a secret place. In this case, a slow charge of the capacitor Sat begins through the resistor R11. At this time, the output of the inverter DD1.4 is low and the capacitors C3 and C4 are discharged. After a time interval of 40 - 50 s, determined by the formula t \u0,7d 6R / IC1.4 (time is in seconds, if the resistance is in megaohms, and the capacitance is in microfarads), a high level is set at the output of the DD1 inverter, and the watchman switches to the mode protection. During this time, the car owner can set the required sensitivity of the SB1 rocking sensor by flashing the HL2 LED, make sure that all doors, hood and trunk are closed (if the HL80 LED is off), exit the passenger compartment and close the door behind him. In the armed mode, the watchman consumes a small current from the battery - less than XNUMX μA.

If the driver's door is opened in the security mode (switch SB2 closes) or the car is rocked (sensor SB1 is triggered), the input of the inverter DD1.2 will close to the vehicle ground. A positive voltage from the output of the inverter DD1.2 will quickly charge the capacitor C3, and after a time t 0,7R10C4 (usually 7 - 10 s) - the capacitor C4. During this period of time, the watchman must be turned off by the SA1 toggle switch, otherwise an alarm will sound.

If you open any car door (except the driver's door), the hood or trunk lid, contacts SB3 - SBn will close, a high level will be set at the output of the inverter DD1.l, and instantly capacitor C6 will be charged through resistor R5 and diode VD4, and capacitor C8 through diode VD3 C1. Turning on the ignition switch will also charge these capacitors (transistor VT1 opens, providing a low level at the input of the inverter DD1.3 and a high level at its output). At the same time, a low level is formed at the output of the inverter DD1.5, which allows the operation of the pulse generator assembled on inverters DD1.6, DD3. Subsequent actions to close the doors, hood, trunk lid and turn off the ignition will not lead to the discharge of capacitors C4 and C5 due to the presence of diodes VD6, VD8, VD1. With the indicated ratings of the circuit elements, the generator generates pulses with a repetition rate of 2-2 Hz, which open the transistor VT40, which switches the winding circuit of the vehicle's VA signaling device. Periodic audible alarms will sound for 60 to 3 seconds. After the discharge of the capacitors C4 and C7, after a time t Q,9R3CXNUMX the watchman switches to the armed mode again.

To bring the guard fi initial state is used toggle switch SA1 with two positions. When the SA1 toggle switch is set to position 2 ("Off"), the capacitor C14 is instantly discharged through the resistor R6 and the watchman is completely de-energized. After switching the SA1 toggle switch to position 1 ("On"), the capacitor C6 is slowly charged, and after 40 -50 seconds the watchman switches to the armed mode. All time delays can be changed by the appropriate selection of the values ​​of the elements of the time-setting circuits.

Elements C7, C8 and VD10 serve to smooth out voltage surges in the on-board network that exceed 15 V and to protect against interference. Diode VD1 protects the transistor VT2 from surges of reverse polarity that occur in the winding of the VA signaling device when it is switched.

The elements of the autoguard circuit are mounted on a printed circuit board made of double-sided foil fiberglass. The drawing of the printed circuit board is shown in Fig.2.

Autoguard on one chip
Ris.2

The rocking sensor consists of three elements: a metal elastic plate A, a rocking plate B, at the end of which a metal weight is attached, and knobs C for adjusting the sensitivity of the sensor (Fig. 2) Due to the asymmetric attachment of the knob to the base of the board, when it is turned, they approach ) or removed (position 1) contact pairs of plates A and B of the sensor. Each time the contact pairs of the sensor are closed, the HL6 LED lights up, which allows you to quickly set the required sensor sensitivity. The sensor sensitivity adjustment knob can be made of any non-conductive material, such as organic glass. The device uses diodes VD1, VD2 -VD4 - any silicon; VD9 - any that can withstand direct current of at least 3 A (for example, type KD0,3, KD208). Diode VD209 is better to choose a pulse from the series KD1, KD521. Instead of the KT522B transistor in the watchman, you can use any type of KT315, KT3102. Transistor KT342A can be replaced with KT829. The KS972Zh zener diode can be replaced with any other with a stabilization voltage of 210 - 8 V. The resistor R9 must be rated for a power of at least 14 watts.

The Sh1 connector is made in the form of contact "knives", which are used as detachable connections in the electrical wiring of cars.

See other articles Section Automobile. Security devices and alarms.

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