Universal security device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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This device is multifunctional and can be used to protect a car (Fig. 1), an apartment (Fig. 2) or a garage. When an alarm is triggered, an audible signal is activated. The device has a built-in power supply and is non-volatile in an emergency. The entire circuit of the device, together with the sound signal, is made in one housing.

Rice. 1. Connecting the security system to the car

When guarding a car, the device works with two types of external sensors: a) for doors (door opening sensors or a mechanical vibration sensor, see the article "Sensors for burglar alarms") - it turns on an audible signal with a delay of 6 seconds; b) for a closed hood and trunk - instant activation of the sound signal.

When an alarm is triggered by the sound, the owner of the guard can easily determine the group of sensors that have triggered during guarding.

After arming, the autoguard circuit provides a delay of 12 ± 2 seconds for leaving the car and 6 ± 1 seconds when entering the car to turn off the alarm with a secretly installed toggle switch S1 until the sound signal is triggered.

Rice. 2. Connecting the security system in the apartment

The wiring diagram of the autoguard (see Fig. 1) ensures blocking of the ignition system (by the second pair of contacts of the toggle switch S1) for the entire time of protection, regardless of the operation of the sensors.

The security device provides LED indication of the alarm sensor operation mode, which is convenient during installation and operation, as it is an indicator of the normal operation of the entire circuit.

The device is powered by the car battery, but in case of an emergency (when it is turned off), the circuit automatically switches to the built-in backup power source, while the current consumed in the ARMED mode does not exceed 0,5 mA.

When guarding an apartment or garage, the device is powered from a built-in power source, which is a block of six A316 cells or NKGTS-0,45 batteries, while the current consumption in the ARMED mode does not exceed 0,5 mA and the batteries will ensure the operation of the device in the ARMED mode at least one year (unless the horn has sounded).

The device works with two lines from sensors:

a) door sensor - turns on the sound signal with a delay of 6 seconds;

b) the sensor of the closed window or the second doors - inclusion of a sound signal instantly.

The watchman circuit provides, after arming, a delay of 12 seconds for leaving the apartment and 6 seconds for entering - to turn off the alarm until the sound signal is triggered.

The alarm circuit has an LED indication of the sensor operation mode, which is an indicator of operation.

The electrical circuit (Fig. 3) is assembled on four CMOS microcircuits of the series, which ensures low current consumption, and consists of a trigger on the elements D1.1 ... D1.3, a generator at a frequency of about 500 Hz - D2.2 and D2.3 , a clock counter D3 and a time interval selection circuit on the D4 chip. Transistors VT1 and VT2 allow you to amplify the current in the load, which is an internal small-sized speaker (ZGDSh-14-4), and an external signal source can also be connected - a car horn.

At the moment the circuit is powered on, the outputs of the counter D3 are set (by the circuit C3, R4) to log. "0". This ensures the appearance of the log. "1" at pin D4/10 and log. "0" on D1/3. In this case, the oscillator and the counter associated with it will work until the moment when "3" appears on the output D2 / 1. If none of the sensors worked, then after 12 seconds a log will appear. "1" on output D1/3 - the generator will stop. From this moment, the device will be in the ARMED mode, and the operation of the sensors will lead to switching the trigger on the elements D1.1 ... D1.3 (log "1" will appear on the output D4/1, and "1" on the output D3/0 "), which will lead to the continuation of the generator and the counter, and an audible signal will appear on the output load after 6 seconds.

Rice. 3 (click to enlarge)

The applied resistors and capacitors can be of any type. All circuit elements, except for the HL1 LED, S1 toggle switch, BA1 speaker, R5 resistor, batteries and sensors, are placed on a single-sided printed circuit board 110x45 mm in size (Fig. 4). In this case, you will need to make six bulk jumpers (if you use a double-sided printed circuit board, then these jumpers are conveniently made with printed conductors).

Transistor VT1 is attached to a heat-dissipating plate (radiator). Toggle switch T1 or any similar one with two switching contacts is used as switch S3.

With proper assembly and serviceable parts, the circuit does not require configuration. The overall dimensions of the entire device, when using a small-sized sound source, do not exceed 140x120x60 mm.

A feature of the above circuit is the absence of electrolytic capacitors, which makes it possible to increase its reliability and expand the operating temperature range for the security device.

Rice. 4. PCB topology and element layout

The given burglar alarm can be easily improved by adding a number of useful functions to it:

• limiting the sounding time (4 ... 5 minutes) of the signal in case of permanent violation of the security loop;
• when the security unit is turned on with a covertly installed toggle switch SA1; if the F1 sensor is in the position shown in the diagram, then regardless of the state of other sensors, the device will wait until it works (for example, when leaving the room), after which the delay time (12 seconds) for turning on the ARMED mode (counting start indicator) will start counting time is blinking green LED HL1);
• upon entering the premises, it is necessary to turn off the alarm within 6 seconds until the alarm sounds, and so that you do not forget that the room was armed, during this time interval the HF1 piezo emitter will emit an intermittent sound signal of low volume.

To perform all these functions, the following nodes were added to the circuit (Fig. 5): a time limiter for the sound signal on the counter D5; trigger on the elements of D6 to provide the standby mode for the start of the countdown of the time interval of 12 seconds. The HL1 LED and the HF1 piezo emitter allow you to more fully control the operating modes of the device, which is convenient during operation.

Rice. 5. Advanced burglar alarm circuit (click to enlarge)

At the initial moment of turning on the power supply of the circuit (A1), the pulse generated by the C4-R5 circuit ensures that the counter D5 is reset to zero (a logical "5" appears at the D7/1 output, i.e., the supply voltage). In this case, the outputs of the circuit elements will have the following states: D6 / 10 - log. "1"; D1/1 - "0"; D1/2 - "0"; D1/3~"1"; D7/1 - "0"; D7/13 - "0".

After the sensor F1 is triggered, a log will appear at the output D6 / 9. "1" (D6 / 10 - "0"), which will lead to the appearance of the output D1 / 3 log. "0". The generator and the counter D3 associated with it will start working, until the time (12 seconds) until the log appears on D4 / 10. "0" (on D1 / 3 - log. "1", which will stop the generator). In this case, the circuit switches to the ARMED mode and will remain in this state until any sensor is triggered.

If one of the sensors F1 or F2 is triggered (when the circuit is in ARMED mode), this will lead to switching the trigger on the elements D1.1 ... D1.3 (log "1" will appear on the output D4/1, and on the output D1 /3 - "0"), which will enable the operation of the generator and counter D3. In this case, after 6 seconds, an audible warning signal (BA1) will appear. During this time interval, it is necessary to turn off the security unit, which, without knowing the location of the SA1 toggle switch, cannot be done by an outsider.

When the F3 sensor is triggered, the audible signal will appear without delay.

When the security unit operates in the NOTIFICATION mode, in addition to the sound signal, the HL1 indicator will glow red. The dual HL1 LED can be replaced with any two ordinary LEDs with a different glow color.

In order to reduce the current consumption of the circuit when the LED is in the indication mode, voltage is applied to it in pulses. Due to the inertia of vision, it is imperceptible.

Rice. 6. Power supply

In stationary conditions, it is better if the device has a mixed power supply - from the mains and the battery. At the same time, the network source is the main one, and in an emergency (when the network is turned off), backup power is automatically supplied from the battery (Fig. 6).

It is convenient to use reed contacts, such as KEM-1, together with a magnet, as sensors F3 ... F1 for signaling. They are small in size and have high reliability. Most often, just one sensor (F1) on the front door is enough.

In case of a short-term operation of the sensors, the circuit from the NOTIFICATION mode automatically returns to the ARMED mode. The duration of the alert tone depends on which sensor has been triggered, and the group of triggered sensors can be easily identified by the sound.

The applied resistors, capacitors and piezo emitter (HF1) will fit any type, small-sized. Instead of KT3102 transistors, you can use KT315G (E), KT3107 is replaced by KT361G (E). Transistor VT5 and stabilizer DA1 are mounted on heat-dissipating plates.

As diodes VD1 ... VD4, any pulse diodes are suitable, VD5 ... VD11 are replaced by KD213A or similar.

For a network power supply, the T1 transformer can be used with a voltage in the secondary winding of 12 ... 16 V and a power of at least 15 W. So, for example, unified transformers of the type are suitable: TPP266-220-50, TPP276-220-50, TPP286-220-50. In this case, during installation, the pin numbering indicated in the diagram is saved.

The security unit is located in a hidden place, and it is better to connect the sensors with wires twisted together, which will eliminate the influence of external induced interference.

With proper assembly and serviceable parts, the circuit starts working immediately and, as a rule, does not require settings.

If necessary, the time intervals of 6 and 12 seconds can be simultaneously changed by selecting the value of the resistor R4. Resistor R13 allows you to limit the sound power in the speaker.

See other articles Section Security devices and object signaling.

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