SU1531121A2 - Device for fire signalling - Google Patents

Abstract

The invention relates to fire-fighting automation and is intended for use in fire protection systems of objects where ignition of flammable substances is possible. The aim of the invention is to improve the functional reliability of the device when exposed to interference. The device contains a photoelectric converter, a band-pass filter, a low-pass filter, an amplitude detector of positive polarity signals, an amplitude detector of negative polarity signals, an AC amplifier, a sampling-storage unit, two differential amplifiers, a null comparator, a division unit, a two-threshold comparator, an output element, comparators and three elements of time delay. Upon termination of interference, the device almost instantly returns to its original state, and when a fire occurs, immediately after the effect the interference is triggered. 2 Il.

Description

The invention relates to fire-fighting automation, is intended for use in fire protection systems of objects where ignition of flammable substances is possible, and is an improvement of the known device according to the author. St.

 1256066.

The purpose of the invention is to increase the functional reliability of the device when exposed to litter.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - time diagram of the operation of bit circuits.

The device contains a photoelectric Converter 1, the band

filter 2, low-pass filters 3, amplitude detector of 4 positive-polarity signals, amplitude detector of 5 negative polarity signals, ac amplifier 6, sampling-storage unit 7, differential amplifier 8, null comparator 9, differential amplifier 10. block 11 divisions, double threshold comparator 12, time delay element 13, output element 14, comparators 15 and 16, time delay elements 17 and 18.

The device works as follows.

In the event of a fire, the photoelectric output

SP

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Converter 1, which is linearly dependent on the magnitude of the luminous flux of flame, enters through the low-pass filter 3 to the positive input of the differential amplifier 10 and to the input of sampling-storage unit 7, and through the band-pass filter 2 to the amplitude detector A of positive polarity signals, amplitude detector 5 signals of negative polarity and amplifier 6 of alternating current. The latter, including the null comparator 9, switches the sampling-storage unit 7 from the sampling mode to the storage mode and continues to receive the output signal of the unit 7, which was before the fire, to the negative input of the second differential amplifier 10, is a voltage corresponding to a monotonically increasing component of the light radiation.

The operation of two chains of device elements: the comparator 15, the time delay element 17 and the comparator 16, the time delay element 18, explains the timing diagram of the operation of the discharge circuits (Fig. 2). The diagram shows diagrams of output voltages of elements 2, 4, 5, 15 - 18.

At time t on the positive input of the comparator 15 the instantaneous value of CD. the output signal of the amplitude detector of signals of positive polarity exceeds in magnitude the instantaneous value of U ,; the output signal of the bandpass filter 2 (since the signal U, j at the time t already passes its maximum); which leads to the triggering of the comparator 15, the activated comparator 15 starts the time delay element 17 having a time delay of 100 ms, but the output signal does not appear, because at time tj the instantaneous value of the signal U becomes less than the instantaneous value of the signal U (due to the increasing character of the burning process) and the comparator 15 returns to the initial state, the delay element 17 also returns to the initial state not typing the time delay, since the signal at its input disappears.

Since at the beginning of the burning of substances, the amplitude of low-frequency scintillations increases (Fig. 2), and the bottom charts

five

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five

0

five

0

five

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That bandpass filter 2 is 10 Hz (oscillation period is 100 ms), then when selecting a time delay of 100 ms, the first element of the time delay is in an inoperative state and no signal is input to the reset input of the amplitude detector of positive polarity signals.

The chain of elements 16 and 18 works similarly. The second comparator operates at the moment of time t, the voltage U of negative polarity and smaller value than the negative voltage at the output of the amplitude detector of signals of negative polarity Uj., and n moment of time t goes into the unworked state. The time duration (tg - tg) is less than the selected 100 ms setting of time delay element 18, so it does not fire and does not send a signal to the reset input of the amplitude detector 5 of the negative polarity signal,

Otherwise, when a fire is detected, the device operates in a manner similar to the well-known: the output signals of the amplitude detector 4 signals of positive polarity and the amplitude detector 5 signals of negative polarity go to the positive and negative inputs of the differential amplifier 8 and to one of the inputs of the dividing unit 11. The signal corresponding to the span of the periodic component of the light emission equal to the sum of the output signals of the amplitude detectors goes to the division unit, where the output signal of the differential amplifier 8 is divided by the output signal of the differential amplifier 10 and, since the output signal of this unit falls within the expected range, This is triggered by a two-threshold comparator 12, the triggering element 13 of the time delay, the latter triggered after 200 ms and turns on the output element 14. The device triggers.

In the case of a change in the illumination of the photosensitive elements of the device during the movement of objects and people, there are 1xC in the viewing angles of these elements, the output signal of the photoelectric converter 1 contains only low-frequency pulsations.

15

which are separated by the band-pass filter 2. The output signal of the band-pass filter 2, amplified by the AC amplifier 6, turns on the null comparator 9 and switches the sampling-storage unit 7 from the sampling mode to the storage mode and the output voltage remains at its output changes in the illumination of the photosensitive elements of the device. But since in this case the output of the low pass filter 3, having a cutoff frequency of 1 Hz, the signal almost remains the same (there is no monotonically increasing component that is characteristic for burning substances), then the output of the differential amplifier 10 has a low signal level and at the output of dividing unit 11, there is a signal corresponding to the depth of the low-frequency pulsations 2 rel. units The device does not work.

The operation of the circuits of elements 15, 17, 16, 18 is explained in the timing diagram of the operation shown in FIG. 2

The timing diagram shows the case of the termination of the specified type of interference, when the output signal of the bandpass filter is in this case decreasing, rather than increasing, as during the occurrence of a flame.

The chain of elements 15 and 17 work

em as follows. When the voltage at the output of the amplitude detector 4 signal of positive polarity is exceeded, the voltage value at the output of the bandpass filter at time t {the comparator 15 is triggered and starts the time delay element 17 and at time t the last one is triggered. The signal from the output of the element 17 of the time delay will be fed to the reset input of the amplitude detector 4 positive polarity signals. The value of the signal U from time t to time tg becomes zero.

one

Q 5 0

five

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with

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Claims (1)

A chain of elements 16 and 18 works in a similar way. Thus, the presence of the considered chains eliminates the inertia of the device. Therefore, at the termination of interference, the device circuit almost instantly returns to its original state (before the appearance of background interference) state, and upon the occurrence of a fire, immediately after the action, the interference triggers. Due to the forced reset of the amplitude detectors 4 and 5, the possibility of a false triggering of the device is also eliminated in the event of a background disturbance associated with movements of objects and people immediately before the appearance of light when the lamp on the control object is turned on, as in this case the occurrence of variable light radiation returns to its original state. The invention of the device for a fire alarm on the author. St. | 1256066, characterized in that, in order to increase the functional reliability of the device, two comparators are introduced into it, the second and third time delay elements, the amplitude detectors are reset, the positive input of the first comparator is connected to the output of the amplitude detector of positive polarity signals, and the negative input of the second comparator is connected to the output of the amplitude detector of negative polarity signals, the negative input of the first comparator and the positive input of the second comparator oedineny a bandpass filter outputs, the inputs of the second and third additional time delay elements are connected respectively to the outputs of the first and second comparators, .a Yield them - to the inputs of peak detector reset signal of positive and negative polarities respectively. yy 13 ifi S0IG.1