Autonomous security device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Safety and security

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Readers are invited to an autonomous security device. In times of lack of free telephone pairs, similar "autonomous" industrial-made, not equipped with the means of transmitting information about an alarming situation to the central security console, equipped many objects where there were material values ​​- warehouses, shops, savings banks, especially in rural areas.

The proposed device is built on the same principle and is also intended for apartments, houses, cottages or garages equipped with several security sensors. A loud alarm will sound when any of them are triggered.

Rice. 1 (click to enlarge)

The scheme of the device is shown in fig. 1. In the author's version, two industrial security sensors were connected to it: surface sound security detector I0329B "Astra-S" (reacts to the destruction of window panes) and an infrared motion sensor "Reflex" by Tehesot. The contacts of the executive relays of these sensors are indicated in the diagram, respectively, K1.1 and K2.1 and are connected in series. As long as the sensors are not powered (voltage 12 V), these contacts are open.

After turning on the device with switch SA1, the voltage stabilizer DA2 is supplied through the diode VD6 from the mains power supply on the transformer T1 and the rectifier on the diode bridge VD1-VD4 or through the diode VD5 from the backup batteries GB1 and GB2. A voltage of 12 V appears at the output of the stabilizer in any case. After 2 s after that, the contacts of the "Astra-C" sensor come into a working closed state, and after 40 s the contacts of the "Reflex" sensor close. The current consumed in rest mode by the first sensor does not exceed 12 mA, the second - 10 mA.

The alarm should not sound until both sensors are in working condition, and the person who turned on the alarm with switch SA1 has not left the protected room or area.

To prohibit its supply for this time (at least 40 s), the DA3 timer generates a 3 high-level pulse of the required duration at its output. It is set with a trimming resistor R10.

During this pulse, the HL2 LED is on (indicating that the security device is in the mode of putting the object under protection), and the transistor VT1 is open. The low voltage level coming from the collector of this transistor to the input E (pin 4) of the DA1 timer maintains the same level at its output (pin 3). Therefore, the sounder HA1 is silent, and the HL1 LED is on. In this state, the timer is insensitive to the voltage level at input S (pin 2), which depends on the state of the sensors.

At the end of the pulse generated by the timer DA3, the transistor VT1 closes. The level at the input E of the timer DA1 becomes high, unlocking it. The HL2 LED goes out, signaling that the object is armed. The DA3 timer no longer affects the operation of the device.

The signal for the operation of the Astra-S sensor is an opening to 7 from contacts K1.1. The voltage level at the input S of the timer DA1 becomes low, and at its output (pin 3) - high. In the timer, the internal transistor closes, the collector of which is connected to pin 7, and the charging of the capacitor C1 through the resistor R1 begins. The HL1 LED goes out, and the sounder HA1 is supplied with power. It beeps at a volume of 105 dB. The current consumed by the detector is 20...40 mA. The signal will sound until the voltage across the capacitor C1 reaches the upper threshold of the timer DA1. The duration of the signal (30 ... 90 s) is set with a trimming resistor R4.

In the case when a person moves in the sensitive zone of the "Reflex" sensor, contacts K2.1 periodically open for approximately 5 s. Each opening triggers the audible alarm process described above. If the repetition period of openings is less than the exposure time of the DA1 timer, the signal will sound continuously and end only after the time set by the trimming resistor R4 after the intruder leaves the sensitive zone of the sensor and the openings stop. If it moves slowly or with stops, the horn may sound intermittently.

In some cases, false alarms of the device are possible, caused by short pulses of interference from nearby electrical equipment, induced on the wires connecting it to the sensors. To get rid of them, you can enter a delay in triggering the alarm by a few seconds. To do this, it is enough to install capacitor C2, shown in the dashed line in the diagram, in parallel with the resistor R2. To obtain the desired delay, the capacitance of the capacitor and the value of the resistor are selected.

It is not recommended to introduce a delay that exceeds the minimum duration of the open state of the sensor contacts when they are triggered (about 5 s). Otherwise, the offender will have the opportunity to "deceive" the security system by moving in a special way.

Fig. 2

The printed circuit board of the device, made of foil fiberglass with a thickness of 1,5 mm, is shown in fig. 2. It is designed for the installation of permanent MLT resistors, KM-6 and K50-35 capacitors (or similar imported ones, suitable in size). Capacitor C3 - K73-17 or K78-2 for a voltage of at least 630 V.

The analogue of the KR1006VI1 timer is any imported microcircuit of the 555 series, for example NE555. The KT315A transistor can be replaced by another device of this series or the KT3102 series. An imported low-power transistor of the p-p-p structure is also suitable. The LEDs of the types indicated in the diagram can be replaced by any that, at a current of 0,5 mA, will provide sufficient brightness.

Transformer T1 - TVK-110LM, modified according to the method described in the article by I. Balonov "On the use of TVK in the power supply" ("Radio", 1984, No. 7, p. 38), or another small-sized one that provides the current of the secondary winding 200. ..500 mA and voltage after rectification (on capacitor C4) 20...35 V.

Krona-VTs (6F22) galvanic batteries were used as backup power sources. The current consumed from them in standby mode does not exceed 30 mA, and when an alarm is given - 50 mA. The operability of the device is maintained when the total voltage of the batteries GB1 and GB2 is reduced to 11 V, and the voltage at the output of the stabilizer DA2 is reduced to 9 V.

When setting up a security device, the engine of the tuned resistor R10 is set to a position in which, after turning on the power with switch SA1, the LED built into the sensor with the longest time to enter the operating mode goes out first (in this case, it is the "Reflex" sensor), and only after 3. ..5 s after that - LED HL2. The desired duration of the alarm sound is set by the trimming resistor R4.

Any number of security sensors can be connected to the described device by connecting their actuating contacts in series. It is limited only by the power of the AC adapter and the capacity of the backup batteries.

Author: S. Semikhatsky

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