RU2221278C2 - Smoke recording gear - Google Patents

Abstract

FIELD: fire alarms, facilities recording smoke while detecting ignition at earliest stages of fire in closed rooms. SUBSTANCE: smoke recording gear has clock generator, radiator coupled through optical camera with light-absorbing walls to photodetector, reset circuit, comparison and storing circuit, former of signal of recorded smoke. Salient feature of gear lies in that it additionally incorporates circuit of synchronous detection and comparison and storing circuit comes in the form of first and second binary counters. V input and R input of first binary counter of comparison and storing circuit are connected to corresponding outputs of clock generator, output of above-mentioned first binary counter is connected in parallel with input of radiator, V input of second binary counter of comparison and storing circuit and first input of synchronous detection circuit which second and third inputs are coupled correspondingly to outputs of photodetector and reset circuit and which second output is connected to R input of second binary counter of comparison and storing circuit. Output of second binary counter of comparison and storing circuit is coupled to C inputs of both binary counters and to input of former of signal of recorded smoke. Synchronous detection circuit has two logic NAND gates, diode, RC circuit. Inputs of first logic NAND gate are coupled to output of photodetector and its output is connected through diode to RC circuit which is coupled to input of second logic NAND gate and through capacitor to output of first binary counter of comparison and storing circuit. Another input of second logic NAND gate is coupled to output of reset circuit and its output is connected to R input of second binary counter of comparison and storing circuit. EFFECT: increased accuracy of gear thanks to elimination of pulse noises while information signal is formed. 1 cl, 2 dwg _

Description

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

 There are known smoke detectors, fire detectors and detectors operating 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, forming a signal about the presence or absence of smoke (see the journal "Communication security systems and telecommunications ", 2000, 33, p.65).

 The IP-212-26 fire optoelectronic detector is known for serial production (see IP-212-26 fire detector. Technical description and operating instructions for BDVK. 425232.001 TO, 1997), which generates periodic bursts of light pulses emitted into an optical camera with light-absorbing walls, and receiving the reflected signals by a photodetector at an angle different from the optical axis of the emitter, which are compared with a threshold value and stored with the subsequent formation of a smoke registration signal, provided that the entire packet of light is received output pulses. The formation of the smoke registration signal is carried out as a result of the operations of comparison and storage. 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 storage circuit. This signal blocks the passage of the counter zeroing signal, which when repeating this situation four times in a row, that is, upon receipt of the entire packet of light pulses, the "fire" mode is registered, after which the environmental density control is terminated.

 A 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 leads to false responses of the sensor.

 As a prototype of the selected device for detecting smoke, described in the patent of the Russian Federation 2134907, 6 G 08 In 17/10, publ. 08/20/99, in which periodic bursts of light pulses are generated that are emitted into an optical camera with light-absorbing walls, followed by the reception of reflected signals at an angle different from the optical axis of the radiation, comparing them with a threshold value and memorizing with the subsequent formation of a smoke registration signal, subject to reception the entire packet of light pulses, and in the intervals between the emissions of light pulses of the packet, when reliable information about the absence of a useful signal with the subsequent formation of a signal on interference and correction of the smoke detection signal.

 If the generated signal is detected by the comparison circuit at the time of interrogation of the optical system, then a counting pulse is generated by the control and storing circuit, which is stored as the “first” burst of the burst, and the smoke detection signal is generated after the entire burst of pulses has been received. During the time intervals between recordings of individual emitted light pulses of the burst, upon receipt of signals exceeding the response threshold, a low-level logic signal is generated, which is sent to the interference detection circuit, and then to the control and memory circuit, resetting the counter and inhibiting the pulse count, thereby preventing the formation of a smoke detection signal.

 At the same time, in the absence of smoke, the appearance of any interference caused by transients causing a decrease in the threshold value and comparable in duration with the duration of the pulse train can generate a false smoke detection signal.

 The specified device has a low noise immunity, and when pulsed noise appears on the input circuits during the passage of the generator pulses caused by both electrical interference and pulsed illumination, for example, when the fluorescent lamps are turned on / off, a signal may decrease below a threshold level. At the same time, reset pulses are generated that arrive at the R-input of the counter, although the level of smoke can exceed the threshold value, which leads to the skipping of the useful signal. In addition, the inclusion of additional circuits directly to the output of the photodiode reduces the sensitivity due to the appearance of additional capacitance and noise immunity due to the long duration of the input circuits.

 The objective of the invention is to increase the reliability of the device by periodically monitoring the sensitive area of the optical camera using synchronous detection for the received reflected signals, which are compared with a threshold value, and according to the results of the comparison, a smoke registration signal is generated corresponding to a change in the density of the environment, as well as an improvement of the known device that reduces the likelihood of a false positive when exposed to light or electromagnetic interference.

 The problem is also solved by the fact that in a device containing a clock generator, an emitter connected through an optical camera with light-absorbing walls to a photodetector, a reset circuit, a comparison and storage circuit, a smoke detection signal generator, an synchronous detection circuit is additionally introduced, and a comparison and storage circuit made in the form of the first and second binary counters, and the V-input and R-input of the first binary counter of the comparison and storage circuits are connected to the corresponding outputs of the clock for generators.

 In this case, the output of the aforementioned first binary counter is connected in parallel with the input of the emitter, the V-input of the second binary counter of the comparison and memory circuit, and the first input of the synchronous detection circuit, the second and third inputs of which are connected respectively with the outputs of the photodetector and reset circuit, and the output is connected with the R-input the second binary counter of the comparison and storage circuit, the output of the second binary counter of the comparison and storage circuit is connected to the C-inputs of both counters and to the input of the shaper of the smoke registration signal.

 In addition, the synchronous detection circuit contains two AND-NOT gates, a diode, an RC circuit, and the inputs of the first AND-NOT element are connected to the output of the photodetector, and the output is through a diode with an RC circuit, which is connected to the input of the second AND gate -NOT and through a capacitor it is connected to the output of the first binary counter of the comparison and storage circuit, the other input of the second logical element AND NOT connected to the output of the reset circuit, and the output to the R-input of the second binary counter of the comparison and storage circuit.

 New in the claimed device is the introduction of a synchronous detection circuit containing two AND gate, a diode, an RC circuit, the inputs of the first AND gate NOT connected to the output of the photodetector, and the output through a diode with an RC circuit, which is through a capacitor connected to the output of the first binary counter of the comparison and memory circuit, and the input of the second logical element AND NOT, the other input of which is connected to the output of the reset circuit, and the output is connected to the R-input of the second binary counter of the comparison and memory circuit. Processing the received reflected signals by the method of synchronous detection and comparing the result with a threshold value eliminates the simultaneous arrival of the reflected signal and impulse noise, and also eliminates the passage of impulse noise affecting the formation of the fire signal.

 In FIG. 1 shows a block diagram for implementing the inventive smoke detection device, FIG. 2 shows an example embodiment of a device for detecting smoke.

 A device for implementing the inventive device for detecting smoke (Fig. 1) contains a clock generator 1, an emitter 2 connected by an optical camera with light-absorbing walls (not shown), a photodetector 3, a synchronous detection circuit 4, a reset circuit 5, a comparison and storage circuit 6, a shaper 7 of the smoke registration signal, while the V-input and R-input of the first binary counter of the comparison and storage circuit 6 are connected respectively to the first and second outputs of the clock generator 1, and its first output is connected in parallel with the input and recipients 2, V-input of the second comparator circuit of the counter 6 and the storage and the first input of the synchronous detection circuit 4, second and third inputs which are connected respectively to the outputs of the photodetector 3 and the reset circuit 5.

 The R-input of the second binary counter of the comparison and memory circuit 6 is connected to the output of the synchronous detection circuit 4, and its third output is connected to the C-inputs of both counters of the comparison and memory circuit 6 and the input of the smoke detector 7.

 A new feature of the claimed device is the introduction of a synchronous detection circuit 4 containing two NAND gates, a diode, an RC circuit, the inputs of the first NAND gate being connected to the output of the photodetector 2, and the output through a diode with an RC circuit, which through a capacitor it is connected to the output of the first binary counter of the comparison and memory circuit 6, and the input of the second NAND gate, the other input of which is connected to the output of the reset circuit 5, and the output is connected to the R-input of the second binary counter of the comparison and memory circuit 6.

 The clock generator 1 generates a sequence of rectangular pulses that is converted by the first counter of the comparison and storage circuit 6 into pulses that determine the time the electrical signals are converted into light emitter 2 and generate counting pulses at the V-input of the second counter of circuit 6 after the RC circuit generates synchronous detection circuit 4 enable signal, which is reset to the second counter of the circuit 6 in the absence of reception of reflected signals by the photodetector 3.

 Since the incoming signals from the photodetector 3 are below the threshold level, the circuit 4 allows the passage of pulses of the reset circuit 5, which reset the second counter of circuit 6. If there is a reception of reflected signals by the photodetector 3, exceeding the threshold value set by the resistor and the second logic circuit of the NAND circuit 4 synchronous detection, they are synchronously detected in this case, the passage of pulses of the reset circuit 5 is blocked and transmitted to the R-input of the second counter of circuit 6, to which the counting pulses are recorded, corresponding to s set signal emitter 2. When a certain number of registered pulse shaper 7 is formed of smoke detection signal.

 This stops monitoring the optical density of the environment, and the generated high-level signal is sent to the output keys, with the help of which the internal resistance is reduced to a predetermined value (no more than 500 Ohms at a current of 20 mA), which is a response signal for the control panel (not shown ) The device is returned to the standby reception after it is disconnected from the power supply for a certain time (at least 1.5 s).

 The smoke detection device can be made, for example, as shown in FIG. 2, from known components. The clock generator 1, made on two AND-NOT gates DD1.1, DD1.2, resistors R1, R2, R3, capacitors C1, C2, and R3, C1 - a circuit forms a time delay of the clock pulses on the second output of the clock generator 1 on 45-50 μs compared to the first output.

The emitter 2, made on transistors VT1, VT2, LED VD3, resistors R5, R6 - forms light pulses of a given duration; photodetector 3 with an amplifier, covered by a negative feedback loop (R14) for constant voltage for resistance to changes in ambient temperature in the range from -25 to +60 ^o С, is made on VT7, VT8 - transistors, UD1 - a photodiode, a multi-stage RC filter - R7C4, R8R9, C5R11R10C6, R15R16C7, eliminating the ingress of impulse noise in the power supply.

 Synchronous detection circuit 4, containing two AND-NOT logic elements DD1.3, DD1.4, a limiting diode VD2, R17C8 is a circuit, and the inputs of the first AND-NOT DD1.3 element are connected to the output of photodetector 3, and the output through the diode VD2 with circuit R17C8 and the first input of the second logical element AND NOT DD1.4, the second input of which is connected to the output of the reset circuit 5, performed on the transistor VT9, resistors R18, R19, R20.

 Scheme 6 comparison and storage is performed on two binary counters DD2.1, DD2.2, and the V-input and R-input of the first binary counter DD2.2 are connected to the corresponding outputs of the clock generator 1, and its first output is connected in parallel with the input of the emitter 2 (R4), the V-input of the second binary counter DD2.1 and the first input (C8) of the synchronous detection circuit 4, the output of which is connected to the R-input of the second binary counter DD2.1, whose third output is connected to the C-inputs of both binary counters DD2 .1, DD2.2 and the input of the shaper 7 signal registration smoke, made on transistors VT3, VT4, resistors R21, R22, R23, R24 and a LED VD4, the anode of which is connected to a power source 8 containing transistors VT5, VT6, resistors R25, R26 and a diode VD5. Contacts 2,2.3,4 provide connection of the device in the line of the control panel (not shown).

 The device operates as follows.

 Clock generator 1 produces rectangular pulses with a period of about 1 s. Circuit R3, C1 forms a time delay at the second output of generator 1 (DD1.2), on which the pulse appears 45-50 μs after it appears on the first output (DD1.1). The pulses from the clock generator 1 are fed to the input of the first binary counter DD2.2 of circuit 6, the output of which is a positive pulse with a duration of the order of 45 μs, which determines the time of emission of the light pulse by the emitter 2. The amplifier of the photodetector 3 amplifies the pulses coming from the photodiode VD1, which then fed to the circuit 4 for synchronous detection AND NOT DD1.3.

 At the same time, a pulse of about 25 μs duration is generated by the R17C8 circuit, which resets the second binary counter DD2.1. For each radiation pulse of emitter 2, the second binary counter DD2.1 of the comparison and memory circuit 6 counts to “1” (pulses from the first output of the first binary counter DD2.2 of circuit 6 are sent to the counting V-input of the second binary counter DD2.1) and reset . The reset pulses of circuit 5 in the absence of a photoresponse reset the second binary counter DD2.1 of circuit 6.

 When smoke appears in the measuring chamber (not shown), the reflected signal from the emitter 2 is amplified by the amplifier of the photodetector 3, which then enters the first input of the second logical element AND-NOT circuit 4, providing a logic level of "1", reset pulses from circuit 5 do not pass and the second logical counter DD2.1 circuit 6 continues the count. The reset pulse of circuit 5 appears after the end of the radiation pulse of the emitter 2 (Fig.3) and coincides in time with the photoresponse of the photodetector 3, because the latter is delayed due to the inertia of the photodiode VD1.

 When smoke appears, counter DD2.1 continues counting (for about 4 s) and when a fourth pulse appears on the third output of the second logic counter DD2.1 of circuit 6, the level of the logic unit appears, which blocks the C-input of the first binary counter DD2.2, turns on LED VD4 of the generator 7 smoke registration and the device goes into fire mode. When the power is turned off for more than 1.5 s, the reset circuit on VT9 closes (at a voltage of about 2.4 V), which leads to the appearance of a logical "1" at the output of the AND-NOT DD1.4 circuit of circuit 4 and the R-input of the second binary counter DD2.1 scheme 6. The device is ready for use the next time you turn on the power source 8.

 Digital signal processing, the use of step filters increases the noise immunity, reliability of the device by eliminating the possibility of false alarms, since interference signals are excluded when generating a “fire” signal, and also simplifies its implementation due to failure, for example, from a high-pass filter in the photo amplifier 3, which allows to reduce weight and size characteristics, cost of products.

Claims (2)

1. A smoke detection device comprising a clock, an emitter connected through an optical camera with light-absorbing walls to a photodetector, a reset circuit, a comparison and memory circuit, a smoke detector, which further has a synchronous detection circuit, and a comparison circuit and storing is made in the form of the first and second binary counters, and the V-input and R-input of the first binary counter of the comparison and storage circuits are connected to the corresponding outputs of the clock gene a radiator, the output of the aforementioned first binary counter is connected in parallel with the input of the emitter, the V-input of the second binary counter of the comparison and memory circuit, and the first input of the synchronous detection circuit, the second and third inputs of which are connected respectively with the outputs of the photodetector and reset circuit, and the output with R- the input of the second binary counter of the comparison and memorization circuit, the output of the second binary counter of the comparison and memorization circuit is connected to the C-inputs of both counters and to the input of the generator of the smoke registration signal. 2. The device according to claim 1, characterized in that the synchronous detection circuit contains two AND-NOT logic elements, a diode, an RC circuit, the inputs of the first AND-NOT element being connected to the output of the photodetector, and the output through a diode with an RC circuit , which is connected to the input of the second logical element AND-NOT and through the capacitor connected to the output of the first binary counter of the comparison and memory circuit, the other input of the second logical element AND-NOT connected to the output of the reset circuit, and the output to the R-input of the second binary counter comparison and memorization schemes.

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