RU2134907C1 - Method and device for smoke recording - Google Patents

Abstract

FIELD: fire alarm. SUBSTANCE: method involves shaping periodic bursts of light pulses emitted into optical chamber provided with light-absorbing walls, receiving reflected signals arriving at angle other than that of optical emission axis both during emission of light pulses and at intervals between light pulses of burst, comparing with threshold value and memorizing them, followed by shaping smoke recording signal on condition that entire burst of light pulses has been received. Device has clock generator, reset circuit, control and memory circuit, optical chamber, photodetector, emitter, comparison circuit, output switching circuit, and noise detection circuit incorporating flip-flop, as well as AND and NAND gates functioning to implement this method. EFFECT: improved noise immunity in fire detection; improved design of device reducing probability of false operation. 2 cl, 2 dwg

Description

 The invention relates to the field of fire alarm, and in particular to methods for detecting smoke, designed to detect fires, accompanied by the appearance of smoke in enclosed spaces, and devices for implementing such methods.

 Smoke detectors, fire detectors and detectors are known that operate on the principle of periodic emission of light pulses and their subsequent reception, and the emitted and received pulses are modulated, compared and processed in various ways, and as a result a signal is issued about the presence or absence of smoke (see Germany s. N 2361403, RF z. N 93021357/09, RF z, N 2037883).

 The prototype of the claimed technical solution was the smoke detection method implemented in a commercially available fire optic-electronic detector IP-212-26 (see, BDVK. 425232.001 TU).

The method of detecting smoke, taken as a prototype, is as follows:
- using a clock circuit, a control and memory circuit, an emitter, periodic bursts of light pulses are generated that are emitted into an optical camera with light-absorbing walls;
- receive the reflected signals by the photodetector at an angle different from the optical axis of the emitter:
- form a smoke detection signal provided that the entire packet of emitted light pulses is received.

 The formation of a smoke detection signal is the result of comparing and storing operations. In the absence of smoke in the sensitive area of the optical camera, the photodetector signal is below the threshold value specified by the comparison circuit. The result of comparing the photodetector signal with a threshold value in the form of a high-level logic signal is fed to the control and storage circuit and allows the passage of the counter zeroing signal. When smoke appears in the sensitive area of the optical camera, light pulses reflected from the smoke particles fall on the photodetector, the signal from which now exceeds the threshold value and from the comparison circuit in the form of a logical zero is fed to the control and memory circuit. This signal blocks the passage of the counter zeroing signal, which upon repeating this situation four times in a row, that is, upon receipt of the entire packet of light pulses, registers the "fire" mode, after which the environmental density control is terminated.

 The disadvantage of the prototype can be attributed to the low level of noise immunity when exposed to light or electromagnetic interference passing through the photodetector, the comparison circuit and the control circuit and memory at the time of interrogation of the optical channel.

 The objective of the present invention is to increase the noise immunity of the method by periodically monitoring the sensitive area of the optical camera using additional methods for determining interference and improving the known device that reduces the likelihood of false alarms.

 The problem is solved by the method of detecting smoke, which consists in the formation of periodic bursts of light pulses emitted into the optical camera with light-absorbing walls, subsequent reception of the reflected signals coming at an angle different from the optical axis of the radiation, comparing them with a threshold value and memorizing, followed by the formation of a registration signal smoke, provided that the entire packet of light pulses is received, and simultaneously receive signals both at the moments of emission of light pulses and in the intervals between the emission of light pulses of the packet, when information about the absence of a useful signal is reliable, with the subsequent formation of a signal of the presence of interference and correction of the smoke detection signal. The problem is also solved by the fact that in a device containing a clock circuit, a reset circuit, a control and memory circuit, an optical camera with light-absorbing walls, a photodetector, an emitter, a comparison circuit and an output key circuit, according to the invention, there is additionally a jamming circuit containing a trigger , logical element AND, logical element NAND, moreover, the trigger reset input is connected to the grounding bus, the trigger installation input is connected to the reset circuit, the trigger data input is connected n a comparison circuit output, and clock input of flip-flop connected to the output member and whose input is connected to the control circuit and the memory, the flip-flop non-inverting output connected to an input of the logical AND-NO element, to second input of which receives a signal from the control circuit and memory.

 Comparison of the proposed method with the prototype shows that, in the presence of features common with the prototype, it differs from the prototype in that it simultaneously receives signals both at the moments of radiation and in the intervals between the emissions of light pulses of the packet, when it is known that there is no useful signal , which allows you to determine the interference and adjust in accordance with this smoke detection signal; that is, the polling frequency of the optical system has increased compared to the prototype.

 The proposed method is implemented in a device, a new feature of which, in comparison with the prototype, is the presence of a noise detection circuit, structurally consisting of a trigger, a logical element AND, a logical element AND-NOT, to the input of which all signals from the comparison circuit are received, and at the output to As a result, an enable or disable signal is received.

 Thus, the claimed method and device meet the criterion of "novelty." The proposed set of operations and techniques characterizing the method allows to increase the noise immunity of the method and reduces the likelihood of a false response of the device. If the signal enters the comparison circuit at the time of the interrogation of the optical system, that is, at the moment of emission of the light pulse of the packet, then the count of the first pulse of the packet is allowed in the control and storage circuit, but since the control and storage circuit issues a response signal to the output key only after receiving and the counts of the entire packet of emitted pulses (in our case, four), and any interference that has passed to the input of the comparison circuit during the time interval between the reception of individual emitted light pulses of the packet and exceeds the threshold yvaniya, produces a logic low level signal which is supplied to the interference determining circuit, and then the control and memory circuit, resetting the counter circuit and prohibiting the count of pulses, the signal interference is not considered, therefore, there is no false operation of the device. Thus, an interference signal interferes with the operation of the device.

 Structurally, this method is carried out by comparing the logical levels of the signals arriving at the interference determination circuit from the comparison circuit, namely, at the trigger data input, the synchronization of which is carried out using the And element in the time intervals between the emission of light pulses and from the non-inverse trigger output to the first input of the AND logic element -Do NOT receive a signal, which, depending on the presence of interference, takes various logical levels, and the signal from the control circuit receives the second input of the logical element AND-NOT Lenia and storing receiving different logic levels depending on whether the useful signal or noise at the instants of the radiation time of light pulses; at the output of the AND-NOT element, an enable or disable signal is generated.

 Thus, the achieved technical result is ensured by the above combination of features characterizing the method and device. Such a performance in the technique is not known, it does not follow directly from the existing level of technology, and was not obvious to specialists. This gives reason to consider these technical solutions as inventive.

 In FIG. 1 is a block diagram of a smoke detection device. In FIG. 2 shows an example implementation of the device.

 The smoke registration device (Fig. 1) contains a clock 1 connected in parallel with a reset circuit 2 and a control and memory circuit 3, the installation input of which and the installation input of the interference detection circuit 8 are connected in parallel with the output of the reset circuit 2, the control output of the control and memory circuit 3 connected to the emitter 4, connected in series with the optical camera 5, a photodetector 6, a comparison circuit 7, the output of which is connected in parallel to the data inputs of the interference detection circuit 8 and the control and memory circuit 3, to the input Allowing the account is connected to the output circuit 8. The obstacle detection resolution Yield account control circuit and memory 3 is connected to an input of multiplying circuit 8 obstacle detection and recording output is connected to an output circuit 9 key.

 The method of detecting smoke is as follows. Using the reset circuit 2, the control and memory circuit 3 and the interference detection circuit 8 are set to the signal receiving mode, the clock generator 1 generates pulses arriving at the control and memory circuit 3. From the control and memory circuit 3, the pulse packets are fed to the emitter 4, which converts electrical pulses in light. In the presence of smoke in the sensitive area of the optical camera 5, light pulses reflected from the smoke particles fall on the photodetector 6, the output signal of which exceeds the threshold set by the comparison circuit 7 and a logic signal of a certain, for example, low level is input to the data of the determination circuit from the comparison circuit 7 interference 8 and the control and memorization circuit 3. In the absence of interference, the interference determination circuit 8 allows pulse counting to the control and memorization circuit 3, which, after counting four pulses in our case, generates a register the signal to the output key circuit 9. In the presence of interference to the input of the data of the interference detection circuit 8 in the time interval between the emissions of light pulses, the interference detection circuit 8 resets the counter in the control and memory circuit 3, thereby inhibiting the counting of the interference signal arriving at data input of the control and memorization circuit 3 from the comparison circuit 7.

 A smoke detector may be implemented, for example, as shown in FIG. 2, from commercially available components.

 Clock generator 1 is made on transistors VT1, VT2, resistor R1, R2, capacitor C1, reset circuit 2 on logic element And D1.1, resistor R3, capacitor C2, control and memory circuit 3 on binary counter D4, trigger D5.1, logical element AND D1.4, logical element AND-NOT D2.2, D2.4, resistor R14, capacitor C6, emitter 4 on LED VD4, photodetector 6 on operational amplifier D3, photodiode VD1, comparison circuit 7 on transistor VT4, output key circuit 9 on transistors VT7, VT8, LED HL1. An additional circuit for determining interference 8 on the trigger D5.2, logical element AND D1.3, logical element AND-NOT D2.3.

 The device operates as follows. At the initial moment of switching on the supply voltage, with increasing voltage on the resistor R1, the clock generator is inhibited and there is a logic level on both inputs of the D1.1 element, which causes a logic level on the inputs 8 and 9 of triggers D5.1 and D5.2, level logical unit at input 8 and the level of logical zero at input 9 of element D2.3, which leads to zeroing the counter D4.2.

Subsequently, the clock generator generates pulses of high duty cycle with a period of T _gene , a logic zero signal is generated on the integrating circuit R3, C2, which removes the level of a logical unit from inputs 8 and 9 of triggers D5.1, D5.2 and the device goes into standby mode.

 The pulse period is set by the resistor R1, the pulse duration is determined by the resistor R2 and the capacitor C1.

From the output of the clock generator, the signal goes to input 1 of the element D4.1. At the input 2 of the element D4.1 there is a signal of a logical unit, therefore, a pulse count is provided along the leading edge. The differentiating chain C6, R14 has a time constant T <T _gene . From output 5 of counter D4.1, through a differentiating circuit C6, R14, a periodic signal with a period T> T _gene is fed to input 13 of element D1.4, where it is multiplied with a clock signal. As a result, at the input of the emitter there is a periodic signal with a period T and a pulse duration set by the clock.

 The periodic signal from the differentiating circuit C6, R14 is multiplied with the clock signal and inverted to the element D2.2, the output of which is fed to the synchronizing input 3 of trigger D5.1, which ensures synchronization of the signal input to the emitter input and the signal from the key VT4 element.

 When binary numbers 0110 and 1110 occur at the output of counter D4.1, from outputs 4 and 5 of counter D4.1, pulses are sent to element D1.3, from output 10 of element D1.3 - to synchronization input 11 of trigger D5.2. The leading edge of the pulse formed by element D1.3 coincides with the time when the VD4 LED is off. Thus, the photodetector signal is recorded after receiving the signal from the emitter.

 If there is smoke in the optical region of the detector, the radiation of the VD4 LED, reflected from the smoke particles, is transmitted to the VD1 photodiode, the pulse signal from which is amplified by VT3 and fed through the operational amplifier D3, isolation capacitor C5, and current-limiting resistor R16 to the key element VT4. When the signal is increased to a threshold value, the transistor VT4 opens and pulses of the zero logic level, synchronous with the pulses of the radiation of the LED, are fed to input 5 of the trigger D5.1. The pulses arriving at input 9 of trigger D5.2 are not fixed by this element at the time of emission by the LED.

 Therefore, at the input 8 and 9 of the element D2.3 there is a signal of a logical unit and pulse counting is allowed for the element D4.2 from the output 5 of the element D4.1. When a sequence of four consecutive pulses arrives, output 13 of counter D4.2 gives a signal of a logical unit, which is inverted by element D2.4 and fed to input 2 of counter D4.1. As a result, pulse counting by element D4.1 is prohibited. At the output 11 of the element D2.4, a logic zero signal is set, the LED switching circuit, the input amplifier circuit and the comparison circuit are turned off.

 From the output 13 of the counter D4.2, the signal of the logical unit goes to the output key circuit, which causes the opening of transistors VT7, VT8 and the flow of current through the indicator element HL1. The internal resistance of the device is discretely reduced. The device registers the "fire" mode and remembers this state.

 If there is light illumination or electromagnetic interference exceeding the permissible values, the signal of the zero logic level from the key element VT4 is fed to the inputs 5 and 9 of the triggers D5.1 and D5.2, which causes the presence of a logic unit at the input 8 of the element D2 during the emission of the LED. 3. The trigger D5.2 also registers an interference signal before and after the emission of the LED VD4 and a logic zero signal is set at the output 13 of the trigger D5.2. A logic unit signal is generated at the output of element D2.3, which prohibits the counting of element D4.2 and does not cause the detector to trigger and switch to the "fire" mode.

 In the absence of smoke and interference, a high logic level is set on the VT4 collector, at the output 2 of trigger D5.1 there is a low logic level, which prohibits the operation of counter D4.2 and prevents the formation of a fire signal by the smoke detector.

 Experimental studies of the inventive device and method showed that, compared with the prototype and the method implemented therein, the noise immunity of the method is increased and the likelihood of false alarms is reduced, since the interference signal (light exposure, electromagnetic interference) is not taken into account when counting the emitted pulses. Thus, the claimed method and device meet the criterion of "industrial applicability".

Claims (2)

 1. The method of detecting smoke, which consists in the formation of periodic bursts of light pulses emitted into an optical camera with light-absorbing walls, the subsequent reception of reflected signals arriving at an angle different from the optical axis of the radiation, comparing them with a threshold value and storing with the subsequent formation of a smoke registration signal subject to the receipt of the entire packet of light pulses, characterized in that the signals are simultaneously synchronized both at the moments of emission of light pulses and between emission of light pulses of the packet, when the information about the absence of a useful signal is reliable, with the subsequent formation of a signal of the presence of interference and correction of the smoke detection signal.  2. A device for implementing a method for detecting smoke, comprising a clock circuit, a reset circuit, a control and memory circuit, an optical camera with light-absorbing walls, a photodetector, emitter, a comparison circuit and an output key circuit, characterized in that it further has an interference detection circuit, containing a trigger, a logical element AND, a logical element AND - NOT, moreover, the trigger reset input is connected to the grounding bus, the trigger installation input is connected to the reset circuit, the trigger data input is connected inen with the output of the comparison circuit, and the trigger synchronizing input is connected to the output of the AND element, the input of which is connected to the control and memory circuit, the non-inverse trigger output is connected to the input of the logical element AND is NOT, the second input of which receives the signal from the control and memory circuit.

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