Improvement of the car guard. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Improvement of the car guard. 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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In "Radio", 2000, No. 10, p. 33, 34 an article by O. Tsitsersky was published "Simple car caretaker", which describes a very successful device for car protection. It was repeated by me many times, while some changes were made to the design aimed at improving performance.

So, if pin 6 of the DD3.2 element (according to the diagram in the mentioned article) is disconnected from pin 5 and other circuits and connected to pin 1 of the DD2.1 trigger, then when the guard is triggered, the HL1 LED stops blinking and stays on. After the watchman enters the armed mode, the blinking of the LED is restored.

This alteration makes it easier to control the state of the device.

The article says that when the supply voltage is applied to the guard, a pulse with a duration of 400 ms will be generated and a short beep will sound, indicating that the security device is turned on. But this signal, in fact, contributes to the unmasking of the power switch.

To avoid this, two ways have been proposed and tested in practice. The first is to exclude the single vibrator DD3.3, DD3.4. The second, which turned out to be more acceptable, is to turn on the watchman with an open switch, while the additionally mounted relay K2 is activated (see the figure), and turn off the relay and the watchman with a hidden button.

Completion of the autoguard

To turn on, the SF3 reed switch was used, installed behind the windshield, next to the signal LED HL1. After getting out of the car, the driver applies a small magnet to the glass opposite the reed switch from the outside and closes the reed switch. The supply voltage is supplied to the autoguard and to the winding of relay K2. It works and contacts K2.1 blocks the reed switch. Now the magnet can be removed, the watchman and the relay will be powered through contacts K2.1, and the relay winding - through the resistor R16, selected for its holding current. Turn off the watchman hidden button SB1.

With the described method of turning on the security device, the time delay for entering it into the watchdog mode becomes unnecessary, so the capacitance of the capacitor C2 can be greatly reduced. It should be borne in mind that this modification increases the current consumed from the battery in armed mode. But since relay K2 switches a small current, you can use a reed relay, for example, RES55A (passport RS4.569.602 or RS4.569.607), or miniature ordinary ones, for example, RES47 (passport RF4.500.407-01 or RF4.500.407-05).

In the original version of the watchman, when any security sensor is triggered, the alarm signal starts sounding after a certain time delay. It would be more correct to have a mode in which the alarm is triggered with a delay when the driver’s door is opened and immediately when any other door, hood and trunk lid are opened, interior windows are broken, etc. This mode is easy to implement if the anode of the VD5 guard diode is disconnected from the microcircuit terminals DD3 and connect to the output of the element DD1.1 (pin 3).

Now the alarm will sound when the SF2 contacts are closed (these are all sensors except the driver's door sensor). If the SF2 contacts are now opened, the signal will stop, but the watchdog will complete the duty cycle and return to the armed mode again. When installing a modified version of the watchman, it is not necessary to install capacitor C7 and resistor R13 on the board, the conductor connecting the anode of the VD5 diode to the DD3 microcircuit must be removed, and the freed inputs of the DD3.3 and DD3.4 elements must be connected to the positive power wire.

The device will still respond with a delay to the activation of the SF1 sensor.

Author: A.Marievich, Voronezh

See other articles Section Automobile. Security devices and alarms.

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