RU2277263C1 - Capacitive device for intruder alarm - Google Patents

Abstract

FIELD: engineering of intruder alarms, namely, engineering of devices for signaling about unsanctioned crossing of blocked boundary by an individual, possible use for developing devices for blocking off portions of closed protected boundary or perimeter of object.

SUBSTANCE: device, containing two sensitive elements in form of capacitive antennae, connected to outputs of primary winding of differential transformer, high frequency filter and relay, additionally includes decoupling transformer, key, voltage splitter and digital signaling processor, input of which is connected to output of high frequency filter, first output - to relay input, second output - to first input of voltage splitter, third output - to first input of key, to second input power is sent, output of which is connected to one of outputs belonging to primary winding of decoupling transformer, another output of which is connected to zero potential point of device, one of secondary winding outputs of decoupling transformer is connected to zero potential point of the sensitive element, another output of which is connected to middle point of primary winding of differential transformer, one of secondary winding outputs of which is connected to zero potential point of device, another output of which is connected to second input of voltage splitter, output of which is connected to high frequency filter input.

EFFECT: increased reliability of device due to increased resistance to interference and resistance to weather effects.

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Description

The invention relates to burglar alarms, and in particular to devices for signaling an unauthorized person crossing a blocked line, and can be used to develop devices for blocking sections of a closed line of protection or the perimeter of an object.

A device for capacitive type alarm systems (AS No. 372571, MKI G 08 V 13/26, BI No. 13, 1973) is known, comprising antennas connected to the ends of the primary winding of a differential transformer, the tap of which is connected to one terminal of the generator, the other the terminal of which is connected to the zero potential bus, the secondary winding of the differential transformer through an amplifier is connected to the signal processing circuit, the primary winding of the differential transformer is asymmetrical.

The disadvantage of this device is the low reliability of the device, low noise immunity, low resistance to weather and climate influences.

The closest in technical essence and the achieved effect to the proposed invention is a capacitive device for burglar alarms (RF patent No. 2010337, IPC G 08 V 13/26, 1994 - prototype), containing two sensitive elements mounted on a protected object, high amplifier frequency filter, low-pass filter, screen, threshold block, the output of which is connected to the input of the Executive unit, a differential transformer, the secondary winding of which is connected to the input of the high-frequency amplifier, alternator one output of which is connected to the zero potential bus, a synchronous detector, a high-pass filter, a DC amplifier, an additional sensitive element is made in the form of a reference capacitor, and the main sensitive element is made in the form of a flat capacitor, one of the electrodes of which is equipped with an insulating adhesive tape and connected with the first terminal of the primary winding of the differential transformer, the second electrode of the flat capacitor is connected through the screen to another terminal of the alternating voltage generator , with the reference input of the synchronous detector and with the midpoint of the primary winding of the differential transformer, the output of the high-frequency amplifier is connected to the information input of the synchronous detector, the output of which is connected to the input of the low-pass filter, the output of which is connected to the input of the high-frequency filter, the output of which is connected to the input of the amplifier DC, the output of which is connected to the input of the threshold unit, the second terminal of the primary winding of the differential transformer is connected to one output of the reference capacitor an amplifier whose other output is connected to the zero potential bus.

The disadvantage of this device is its low reliability due to low noise immunity and low resistance to climatic influences.

In this device, exposure to a sensitive element of a noise with a frequency close to the frequency of an alternating voltage generator or a broadband signal with a spectrum that covers the passband of a bandpass filter leads to a false response of the device.

When using this device to protect the perimeters of extended objects as a result of changes in weather and climate conditions (for example, snow sticking to a sensitive element), the capacitance of the sensitive element will change, the differential transformer will be unbalanced and, as a result, the high-frequency amplifier will become saturated with a sharp loss of sensitivity devices in general.

The aim of the present invention is to increase the reliability of the device by increasing the noise immunity and resistance to weather and climate influences.

To achieve this goal, a decoupling transformer 6, a key 7, a voltage divider 8 and a digital signal signal are introduced into a device containing two sensitive elements in the form of capacitive antennas 1, 2 connected to the terminals of the primary winding of a differential transformer 3, a high-pass filter 4 and a relay 5 processor 9, the input of which is connected to the output of the high-pass filter 4, the first output is with the input of the relay 5, the second output is with the first input of the voltage divider 8, the third output is with the first input of the switch 7, the second input of which is supplied with power e, the output of which is connected to one of the terminals of the primary winding of the isolation transformer 6, the other terminal of which is connected to a point of zero potential of the device, one of the terminals of the secondary winding of the isolation transformer 6 is connected to a point of zero potential of the sensing element, the other terminal of which is connected to the midpoint of the primary winding differential transformer 3, one of the terminals of the secondary winding of which is connected to the point of zero potential of the device, the other terminal of which is with the second input of the divider zheniya 8, whose output is connected to the input of the high pass filter 4.

A comparative analysis of the claimed device with the prototype shows that the proposed device is characterized by a new structural embodiment of the elements, their location in the circuit. Therefore, the proposed solution meets the criteria of the invention "technical solution".

Comparison of the claimed solution with other technical solutions in this technical field did not reveal the signs that distinguish the proposed solution from the prototype, which makes it possible to conclude that the criteria of the invention are met: "novelty", "significant differences" and "positive effect".

Figure 1 presents the structural diagram of the proposed device; figure 2, 3 are graphs explaining the operation of the device.

The following notation is accepted:

1, 2 - capacitive antennas;

3 - differential transformer;

4 - high-pass filter;

5 - relay;

6 - isolation transformer;

7 - key;

8 - voltage divider;

9 - digital signal processor.

The proposed device operates as follows. The digital signal processor 9 generates the triggering pulses, closing the key 7 (figa, where U is the voltage at the third output of the digital signal processor 9; 1 - the first triggering pulse, 2 - the second triggering pulse, ... I - I-th triggering pulse etc.). Wherein the probing pulse duration τ _and selected in such a way that after opening of the key 7 in the primary winding of the differential transformer 3 arise free damped oscillations whose amplitude is proportional to the difference in capacitances antennas 1, 2 (2b, where V - error signal at the output of differential transformer 3 ; 1 - the first implementation of the error signal, 2 - the second implementation of the error signal, ... I - I -th implementation of the error signal, etc.). An isolation transformer 6 is used to galvanically decouple the points of zero potential of the device and capacitive antennas 1, 2 and thereby increase the noise immunity of the device.

The repetition period of the trigger pulses (T _u ) is selected from the condition:

T _u = T ₁ + T ₂

where T ₁ = const

T ₂ is a random variable in the range from 0 to T ₂ , where T ₂ > T ₁ .

The error signal from the output of the secondary winding of the differential transformer 3 through a voltage divider 8 and a high-pass filter 4 is fed to the input of a digital signal processor 9, where it is digitized with a period ΔT (Fig. 3).

t _i = ΔT

i = 1,2 ... K

равно значению i-й выборки, I-й реализации сигнала рассогласования;Where

equal to the value of the i-th sample, I-th implementation of the error signal;

K is the number of samples of the error signal.

During the time remaining after digitization before the end of the current period T _n , the digital signal processor 9 performs the following operations:

1) for each i-th sample (i = 1, 2 ... K) it calculates the first and second current average amplitude values:

1st current average

2nd current average

where M> L

2) calculates the average value for all K samples:

and compares with its threshold value.

In the absence of the intruder’s impact on the capacitive antennas 1,2, the mismatch signal changes only due to changes in weather and climate conditions (since the antennas cannot be exactly the same, their own capacities change differently with changes in weather and climate conditions), t. e. slow enough. The ratio of the averaging periods L and M is chosen so that, for any change in weather conditions, the average value is less than the threshold value.

превысит пороговое значение и цифровой сигнальный процессор 9 подаст напряжение на обмотку реле 5, выставив тем самым сигнал тревоги.When an intruder acts on one of the antennas 1,2, a rather rapid change in the error signal will occur,

will exceed the threshold value and the digital signal processor 9 will apply voltage to the coil of the relay 5, thereby setting an alarm.

The presented algorithm is a software implementation of a band-pass filter, the upper and lower boundary frequencies of which are determined by the values of L and M averaging periods.

, будет равен 0.The impact on one of the capacitive antennas 1, 2 interference (for example, a sinusoid) with a frequency in the passband of the band-pass filter, will not lead to a false response of the device, because the phase shift between the triggering pulses and the sinusoid will vary randomly and for sufficiently large values of L and M the interference contribution to the first and second current average, and therefore to

will be equal to 0.

Claims (1)

A capacitive device for burglar alarm, containing two sensing elements in the form of capacitive antennas connected to the terminals of the primary winding of a differential transformer, a high-pass filter and an actuating unit in the form of a relay, characterized in that an isolation transformer, a key, a voltage divider and a digital signal are introduced into it a processor, the input for receiving the mismatch signal of which is connected to the output of the high-pass filter, the first output for supplying an alarm signal - with the input of the executive unit in de relay, the second output for matching the mismatch signal with the input range of the built-in analog-to-digital converter of the digital signal processor - with the first input of the voltage divider, the third output for supplying a triggering pulse - with the first input of the key, the second input of which is supplied with power, the output of which is connected to one of the terminals of the primary winding of the isolation transformer, the other terminal of which is connected to a point of zero potential of the device, one of the terminals of the secondary winding of the isolation transformer the ora is connected to the point of zero potential of the sensing element, the other terminal of which is connected to the midpoint of the primary winding of the differential transformer, one of the terminals of the secondary winding of which is connected to the point of zero potential of the device, the other terminal of which is connected to the second input of the voltage divider, the output of which is connected to the input of the filter high frequencies.

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