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Remote security devices infrared car

Remote security devices infrared car

In this section, we will consider security devices with remote control on infrared rays, which allow disabling the alarm without touching the car, and abandon the delay in switching the system into armed mode. The time delay is sometimes enough for the “expert” to open the hood and disconnect the battery, and then deal with the alarm in a calm environment.

Of course, there are scanners of domestic and imported production, with the help of which by selecting combinations of pulses, their duty cycle and period, you can reveal the alarm code on infrared rays. Therefore, there will be considered remote security devices on IR rays, which use information coding based on other physical principles that are not available to modern scanners.

Auto guard on infrared rays

This is a remote control system with frequency coding and long-term exposure to the photodetector. Of course, frequency coding is not the top of perfection, but, nevertheless, it works effectively. In order for the frequency of the scanner at a certain moment to not accidentally coincide with the frequency of the auto-watch , a 2-second time delay is used, which almost completely excludes random selection of the frequency.

The auto-guard includes a remote control on infrared LEDs of the type AL107B, made according to the well-known scheme. Also, the K176IE12 microcircuit and a quartz resonator Q 1 with a frequency of 32768 Hz for the formation of time intervals are included in the auto guard .

Main technical characteristics of the device:

Time of transition to protection mode, with                                                                                                                20

Alarm duration, s                                                                                       40

Alarm interruption frequency, Hz                                                                                                      one

Alarm delay time, s                                                                                          2

Current consumption in protection mode, not more, mA                                                                                       ten

PCB dimensions, mm                                                                                                                           60x65

Dimensions of the control panel, mm                                                                                                                     25x30

The schematic diagram of the remote control is shown in Fig. 4.27. The console includes a multivibrator on the elements DD 1.1 - DD 1.3, an inverter DD 1.4, a pulse switch on transistors VT 1, VT 2 and infrared light-emitting diodes VD 1, VD 2. The frequency of the multivibrator is adjusted by adjusting the resistance of the R 1. Resistance printed circuit board is shown in fig. 4.28. To power the remote, you can use the battery "Krona", which will ensure its long use.

The schematic diagram of the auto guard is shown in fig. 4.29. The auto-watch contains a counter-shaper of time intervals on a DD 2 chip, two triggers on DD 1.3, DD 1.4 and DD 3.2, DD 3.3 elements, a receiving device on a DD 4 chip with a VD 6 photodiode and a key on VT 2, VT 3 transistors.

When the device is powered on with the SA 1 toggle switch (before leaving the car), the capacitor C 1 with its charging current sets the counters of the DD 2 chip to the initial zero state. On pin 10 of the DD 2 chip at this time log. "0", which enters the input element DD 3.4 and opens it. From pin 6 of DD 2 chip, 2 Hz pulses go through DD 3.4 and arrive at clock input C (pin 7) of DD 2. At the same time, the zero level at pin 10 of DD 2 chip, inverted by DD 3.1, blocks the trigger, collected on the DD 3.2 and DD 3.3 elements, and prohibits the passage of a signal from the contact sensors SB 1 - SBn connected to the cathode of the VD 3 diode through the transistor VT 1 to the elements DD 1.1 and DD 1.2. The guard is in this state until the counter DD 2 counts 39 pulses with a frequency of 2 Hz. This time of 20 s gives the car owner the opportunity to leave the cabin and close all doors. After this time, a unit appears on pin 10 of the DD 2 counter, which closes the DD 3.4 element   and prohibits the arrival of counting pulses with a frequency of 2 Hz at the counting input C DD 2. The same signal (log. "1"), acting on the inputs of the DD 3.1 element, unlocks the trigger on DD 3.3, DD 3.2, and the circuit goes into vehicle protection mode.

As contact sensors, you can use the car door switches. The same pushbutton switches can be put on the hood and on the trunk lid. The cascade on the transistor VT 1 serves as an inverter and at the same time protects the DD 3 microcircuit from failure when a positive voltage is applied to its output 1 at a time when the power of the auto-guard is turned off. When one of the contact sensors SB 1 - SBn is triggered, the cathode of the diode VD 3 closes to ground, the transistor VT 1 closes and a positive potential is set on its collector, which switches the trigger on the DD 3.3, DD 3.2 elements. At the same time on its output 4 the log level is set. " I ". With the output of the inverter DD 1.1 log. "0" goes to pin 1 of DD 1.2 and opens it. From pin 4 of the DD counter, 2 second pulses through the DD 1.2 element are fed to pin 7 of the DD 2 counter and the key on transistors VT 2 and VT 3, which turns on the K 1 audio signal relay. The DD 2 counter counts 39 pulses arriving at pin 7, and after 40 s it is set to the zero state (at pin 10 - the log. "0"). Then, according to the scenario described above, there is a 20 second delay (as when the power is turned on), and the circuit goes back into protection mode.

To turn off the auto guard, use the control panel, which emits pulses in the infrared range . A photodetector consisting of a photodiode VD 6 and a resonant amplifier on elements DD 4.1 - DD 4.3, receives a signal from the remote control panel. The frequency to which the device reacts is set by the elements of the circuit L 1, C 9. Its resonant frequency should correspond to the frequency of the console's multivibrator. The signal from the resonant amplifier is fed to a constant voltage driver. When the frequencies of the contour L 1, C 9 and the multivibrator of the control panel correspond, the level log appears at the output 10 of the DD 4.5 element. " I ". In order to exclude the operation of the auto-guard in case of accidental coincidence of the frequencies of the device and the scanner by the R 19, C 11 circuit, a time delay of 2 s is formed .

After charging the capacitor C 11, the signal arrives at pin 8 of the trigger on the elements DD 1.3, DD 1.4, which at pin 11 forms a positive pulse arriving at pins 5, 9 of DD 2, and resets the counter. The moment the device is turned off is indicated by the HL 1 LED.

The printed circuit board of the auto guard is shown in fig. 4.30. The coil L 1 is wound on the core of the SBR-23 and contains, depending on the frequency from 100 to 500 turns (from 16 kHz to 5 kHz, respectively) wires PEV-1 0.1 mm . To power the chips in the circuit, a Zener diode VD 5 of the type KC 210 is used with a stabilization voltage of 10 V.

The location of the parts on the circuit board of an auto guard is shown in fig. 4.31.

Setting up the auto guard is reduced to setting the frequency of the circuit with the elements L 1, C 9 and interfacing with it the frequency of the multivibrator of the remote control by selecting the resistance of the resistop R 1, achieving reliable and stable operation of the device.