UA78837C2 - Smoke detector - Google Patents

Abstract

The proposed smoke detector is designed for detecting smoke by the change of infrared radiation intensity caused by increased air density. Additionally, the detector contains a controlled timing pulse generator, which is switched on depending on the power-supply voltage, elements for isolating the detector electric circuits, and filters. The said additional unit and elements as well as the connections between the units and elements provide a possibility to exclude the reduction of the power-supply voltage of the logic elements of the smoke detector to the level below the allowable level and, as a result, enhance the reliability of the operation of the detector in fire.

Description

Description of the invention

The invention relates to the field of fire alarm and can be used in fire alarm systems to detect the increase in the optical density of air by the intensity of infrared radiation scattering.

Known fire detectors, optical smoke detectors and smoke registration devices that work on the principle of periodic emission of infrared light pulses and their subsequent reception, amplification and processing of the received signal in various ways, forming a signal about the presence or absence of smoke | see 70 magazine "Sistem! bezopozanosti svyazii i telekommunikatsii", 2000, 33, p. 651.

Known smoke detection device (patent of the Russian Federation of CI) 2221278, MPK7 508817/10, publ. 2004.01.10Y, containing a clock generator, an emitter connected through an optical camera with light-absorbing walls to a photoreceiver, a reset circuit, a generator of a smoke registration signal. In addition, it contains a synchronous detection circuit, a comparison and memory circuit, which is made in the form of 12 first and second binary counters, and the M-input and K-input of the first binary counter of the comparison and memory circuit are connected to the corresponding outputs clock generator, the output of the mentioned first binary counter is connected in parallel with the emitter input, the M-input of the second binary counter of the comparison and storage circuit and the first input of the synchronous detection circuit, the second and third inputs of which are connected to the outputs of the photodetector and the reset circuit, respectively , and the output is connected to the K-input of 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 smoke registration signal generator.

The disadvantage of the known device is the low reliability of its operation, especially at low, for example, less than 0.1 ma, power supply current. Logical nodes made on CMOS microcircuits, after turning on the power supply when reaching the operating voltage (more than 3 V), significantly increase the current consumption, especially those nodes that are covered by feedback: generators, boundary elements, etc. Moreover, with an increase operating voltage Ge) the current consumption increases, for example, the current consumption of the generator at the maximum value of the operating voltage can reach the value of units of milliamps, i.e. exceed the set limit of current consumption in general for the detector by several times.

The closest to the proposed invention is the smoke fire detector chosen as a prototype

Optical-electronic fire alarm MIP212-41 M; TU 4371-005-12215496-00; Passport "95 4371-005-12215496-00 PS containing an element of one-way conduction, the input of which is connected to the first terminal for connection to the fire alarm loop, and the output is connected to the first output of the power supply of the generator of the smoke detection signal and the input of the current limiting element, the output of which is connected to the first output of the capacitor, the second output of which is connected to the common bus, to the second terminal for connecting to the fire alarm loop 39 and to the second output of the power supply of the signal generator in smoke registration, the output of which is connected to the indicator, and the input - to the output of the binary counter, to the C-input of this counter and to the first input of the clock generator, the first output of which is connected to the M-input of the binary counter and the first input of the comparison circuit, the output of which is connected to the K-input of the binary counter, " the second input of the comparison circuit is connected to the output of the amplifier, and the third input - to the output of the reset circuit according to the supply voltage, to the inputs of the amplifier will be connected nth photodiode, optically connected through a camera with light-absorbing walls to an infrared emitter, connected to the output of a current switch, the first power terminal of which is connected to the first terminal of the capacitor and the input of the integrator, the output of which is connected to the first power terminal of the amplifier, the second the power output of which is connected to the second power output of the current switch and the common bus.

The disadvantage of the known detector is also low reliability, especially with a small, for example, less than 0.1 ma, 7 power supply current. If the amount of current consumed by the amplifier, the clock generator, the comparison circuit, the reset circuit according to the supply voltage, the binary counter, the current switch, together with the leakage current of the capacitor, reaches the value set by the current limiting element, then it is possible

So blocking the further increase of the voltage drop, which may never reach a value equal to or greater than 20 of the lower value of the operating voltage of the logic elements. This means that, consuming the set value of the current from the fire alarm loop, the detector may not go into the next mode of operation at any time when the power supply voltage is turned on. Moreover, the fact of such refusal can be established after the whistleblower fails to fulfill his main function. In addition, with any subsequent switching of the power supply voltage in the fire alarm loop, failure of any similar detector 22 installed in this fire alarm loop or restoration of the regular mode of operation of the detector may occur

GF) in a chaotic manner.

With a completely discharged capacitor, the leakage current at the initial moment after switching on reaches the value limited by the current-burning element, and then slowly, over several minutes, it will reach a value equal to 60 Ivit: KСО 5. А,

Ivit is the leakage current of the capacitor;

K is a coefficient that depends on the type of capacitor, for example, 0.05 - for capacitors of the K5O-6 type;

C - capacitor capacity, in microfarads;

Y - operating voltage of the capacitor in Volts; because A is a constant value of the leakage current, for example 5 μA - for capacitors of the KBO-6 type.

For example, for a capacitor of this type with parameters of 47 μF, 25 V used in a detector, the amount of leakage current may exceed the rated current consumption of the entire detector

IP212-41M - 50 μA. Thus, when such a detector is turned on, the voltage drop on the capacitor can be blocked by an amount less than C V, when the logic states at the outputs of the logic elements have not yet been determined.

It is possible to reduce the influence of leakage currents by choosing the type of capacitor used, but it is impossible to completely exclude the influence of charge current and capacitor leakage current. It is necessary that the current passing through the current-limiting element significantly exceeds the leakage current of the capacitor being used.

If the prototype has a direct galvanic connection between the clock generator and the current switch, the 7/o voltage level at the output of the clock generator may be sufficient to open the current switch even before the voltage drop on the capacitor reaches the value of the operating voltage of the logic elements. In this case, the current flowing through the infrared emitting diode will further reduce the charge current of the capacitor, which means that the voltage drop across the capacitor may never reach the operating voltage of the logic elements. In this state, the detector can stay indefinitely without performing its main function. Logic elements covered by negative feedback, for example, those on which the clock generator is assembled, can also contribute to the failure of the detector. It is these logic elements that consume a significant part of the current flowing through the current-limiting element, because most of the time they are in an active state - in the process of switching. Therefore, when the supply voltage is turned on, the logic elements of the clock generator sharply increase the current consumption in conditions when the voltage drop on the capacitor reaches the value of the minimum 2o operating voltage. This can lead to a decrease in the voltage drop on the capacitor and prevent further growth of the voltage drop on the capacitor.

The invention is based on the task of increasing the reliability of the detector by eliminating the effect of blocking the voltage drop on the logic elements at a value smaller than the minimum value of the operating voltage of these logic elements. high school

The task is solved by the fact that a smoke fire detector containing an element of one-way conduction, the input of which is connected to the first terminal for connection to the fire alarm loop, and the output (8) is connected to the first output of the power supply of the generator of the smoke detection signal and the input of the current limiting element, the output of which is connected to the first output of the capacitor, the second output of which is connected to the common bus, to the second terminal for connecting to the fire alarm loop and to the second M with the output of the power supply of the generator of the smoke registration signal, the output of which is connected to the indicator, and the input is to the output of the binary counter, to the C-input of this counter and to the first input of the clock generator, the first and, the output of which is connected to the M-input of the binary counter and the first input of the comparison circuit, the output of which is connected to the K-input of the binary counter, the second the input of the comparison circuit is connected to the output of the amplifier, and the third input is connected to the output of the reset circuit according to the supply voltage , a photodiode is connected to the inputs of the amplifier, so

It is optically connected through a camera with light-absorbing walls to an infrared emitter connected to the output of a current switch, the first power output of which is connected to the first output of a capacitor and the input of an integrator, the output of which is connected to the first power output of an amplifier, the second power output of which connected to the second power output of the current switch and the common bus, according to the invention, additionally contains a high-pass filter, the output of which is connected to the input of the current switch, and the input - to the second output of the clock generator, the second input of which is connected to the output of the voltage reset circuit power supply, the terminals of the power supply of which are connected to the corresponding power terminals of the amplifier, clock generator, binary counter and comparison circuit. ;" Due to the introduction of the control circuit of the clock generator from the reset circuit according to the supply voltage, a reduction in current consumption by the logic elements of the clock generator is ensured at the first moment

Turning on the power supply. This reduction is due to the fact that the clock generator starts to work after the voltage drop on the logic elements exceeds the minimum value of the operating voltage. Separation of the input circuit of the current switch from the second output of the clock generator with the help of a high-frequency filter ensures reliable maintenance of the current switch in the closed state in the absence of pulses at the output o of the clock generator, and thus - a reduction in the current consumption of the current switch at the time of switching on the 5o detector. Separation of the power supply circuits of the current switch from other elements of the circuit with the help of an integrator ensures the creation of a difference in voltage drops on the current switch and on the logic elements of the "M" circuit of the detector. Due to this potential difference, stable operation of the detector is ensured, because short-term voltage drops at the terminals of the capacitor in moments its discharge with a current switch does not change the potential of the bus from which the logic elements are powered. All this makes it possible to exclude the effect of blocking the voltage drop on the logic elements at a value lower than the minimum value of the operating voltage of these logic elements, and to ensure stable start-up of the detector circuit at each voltage switch-on ( F, power supply. The figure shows a block diagram of a smoke fire detector.

The smoke fire detector contains indicator 1, as well as terminals 2 and 3 for connection to the fire alarm loop. The input of the element 4 of one-way conduction is connected to the first terminal 2, the output of which is connected to the first power output of the generator 5 of the smoke detection signal and the input of the current limiting element 6. The output of the current limiting element 6 is connected to the first output of the first capacitor 7, the power output of the current switch 8 and the input integrator 9. The output of the integrator 9 is connected to the first power output of the amplifier 10, the second power output of which is connected to the common bus 11, the second terminal C and 65 to the second power output of the generator 5 of the smoke registration signal, to the output of which the indicator 1 is connected.

The power terminals of the circuit 12 reset by the supply voltage are connected to the corresponding power terminals of the amplifier 10, the clock generator 13, the comparison circuit 14, the binary counter 15. A photodiode 16 is connected to the inputs of the amplifier 10, optically connected through a camera 17 with light-absorbing walls to the infrared the emitter 18 connected to the output of the current switch 8. The input of the generator 5 of the smoke registration signal is connected to the output of the binary counter 15, to the C-input of this counter 15 and to the first input of the clock generator 13, the first output of which is connected to the M-input of the binary counter 15 and the first input of the comparison circuit 14, the output of which is connected to the K-input of the binary counter 15, the second input of the comparison circuit 14 is connected to the output of the amplifier 10, and the third input is connected to the output of the reset circuit 12 by the supply voltage and to the second input of the clock generator 13. The second output of the clock generator 13 through the high-frequency filter 19 7/0 is connected to the input of the current switch 8. To the output of other tegrator 9, a power bus 20 is connected, from which the following are powered: amplifier 10, circuit 12 reset by supply voltage, clock generator 13, circuit 14 comparison and binary counter 15. In the figure, the power outputs of circuit 12 reset by supply voltage, clock generator 13, circuit 14 comparator and binary counter 15 are not shown.

A smoke fire alarm works like this. When the supply voltage is applied to the input terminals 2 and C through element 4 of one-way conduction and current-limiting element b, the storage capacitor 7 is charged. Element 4 of one-way conduction protects other elements of the smoke fire alarm in case of wrong connection of the polarity of the supply voltage of the fire alarm loop.

While the voltage at the terminals of the storage capacitor 7 is insufficient for the normal operation of the smoke fire detector, the voltage drop at the integrator 9 is insignificant - much less than the voltage drop between the power bus 20 and the common bus 11. This is due to the low current consumption of the logic elements in static mode. Even before the minimum value of the operating voltage is reached at the output of the circuit 12 reset by the supply voltage, a low potential level is formed, which prohibits the operation of the clock generator 13. But at these voltages, there are potentials at the outputs of the clock generator 13 that are close to half of the voltage drop at the supply terminals of the clock generator 13. The upper frequency filter 19 does not allow the current switch 8 to open. At the moment of reaching the minimum value of the operating voltage, all elements of the detector circuit i) are in static mode. At the first output of the clock generator 13, a low potential level is set, and at the second - its inverse value: a high potential level. The low potential level coming through the third input of the comparison circuit 14 sets the K-input of the binary counter 15 M zo to a high potential level. In this case, the binary counter 15 is in the zero state regardless of the signals at its other inputs. Generator 5 of the smoke registration signal is closed and indicator 1 is turned off. At the same time, the low potential level coming from the output of the binary counter 15 to the first input of the clock generator 13 and to the C-input of the same counter 15 enables the operation of the clock generator 13 and the binary counter 15.

Since the current consumption of the clock generator 13 significantly depends on the supply voltage, for its small (tens of microamperes) value, it is necessary that the switching of the reset circuit 12 according to the supply voltage is carried out at an operating voltage close to its minimum value, but exceeding it. At the moment of change of state at the output of the circuit 12, reset by the supply voltage, the clock generator 13 is started, and the potential level is set at the K-input of the binary counter 15, which allows the change of states of the binary counter 15 " during voltage drops at its M-input. From this moment, the voltage drop between the supply bus 20 and the common bus 11 stabilizes, and the voltage drop on the storage capacitor 7 continues to increase.

Approximately 1 second after enabling work on the mutually inverse outputs of the clock generator 13 ;" a short pulse lasting several tens of microseconds appears. With the same duration and frequency of about 1 second, the pulses at the outputs of the clock generator 13 are repeated until the appearance of prohibiting signals 45. At its inputs. From the first output of the clock generator 13, pulses are sent to the first input of the circuit 14 - I comparison and the M-input of the binary counter 15. From the second output of the clock generator 13, through the high-frequency filter 19, the pulses are sent to the input of the current switch 8. The current switch 8 provides a discharge of the storage so capacitor 7 with a given amount of current through its output to the infrared emitter 18. The value, on

Go! which the storage capacitor 7 discharges depends on the duration and period of the pulses appearing at the output of the clock generator 13, as well as on the ratio of the charge current of the storage capacitor 7 o through the current limiting element 6 to the discharge current of this capacitor 7 through the current switch 8. Thus

In the first way, the set voltage drop on the storage capacitor 7 exceeds the potential of the power bus 20 by the amount of the voltage drop on the integrator 9. Due to this potential difference, stable operation of the detector is ensured, because short-term voltage drops at the terminals of the storage capacitor 7 dv at the moment of its discharge by the current switch 8 due to the integrator U do not change the potential of the power bus 20.

F) Scattered by the optical chamber 17 with light-absorbing walls, the infrared radiation of the emitter 18 enters the photodiode 16. The amplitude and phase of the pulses amplified by the amplifier 20 depend significantly on the optical density of the air in the optical chamber 17. Thus, with absolute transparency of the air at the output of the amplifier 10 small-amplitude triangular pulses are present because some reflection from the walls of the optical chamber 17 takes place. reset pulses of the binary counter 15 appear. Thus, after each positive signal drop at its M-input, the binary counter 15 switches, counting only one 65 pulse, and is immediately reset from the pulses arriving at its K-input. In the alternate mode of operation, when the specific optical density of air is below the set level, the binary counter 15 is reset after each pulse at the output of the clock generator 13. A low potential level remains at the output of the higher digit of the binary counter 15, to which the input of the generator 5 of the smoke registration signal is connected , indicator 1 does not light up. The detector remains in the regular mode of operation, consuming current from the fire alarm loop connected to terminals 2 and 3, the value of which is limited by the current limiting element 6.

As the specific optical density of the medium increases, the amplitude of the pulses at the output of the amplifier 10 increases until it reaches the limit value, at which a low potential level is set at the K-input of the binary counter 15, which allows the counting of pulses arriving at the M-input 7/0 of the Counter 15. In this case, for each pulse at the output of the clock generator 13, the state of the binary counter 15 increases by one, until the switching of the higher digit of the binary counter 15 occurs, which prohibits the further counting of pulses corresponding to the state of the "FIRE" detector. If there is a high potential level on the higher digit of the binary counter 15, the shaper 5 of the smoke registration signal is opened, which provides the specified current consumption from the fire alarm loop, to which the smoke fire detector is connected with its input terminals 2 and 3. In addition, this signal prohibits the operation of the clock generator 13. In this state, the current consumption of the clock generator 13, the amplifier 10 and other elements of the circuit is significantly reduced, at the same time, due to the current flowing through the generator 5 of the smoke registration signal, the potential difference between terminals 2 and 3 is sharply reduced. If this is a voltage drop exceeds the minimum value of the operating voltage, the detector remains in the "FIRE" state indefinitely. It is possible to remove the detector from this state only by disconnecting the power supply voltage of the fire alarm loop for a time sufficient to discharge the storage capacitor 7 to the value at which a low potential level will be established at the output of the reset circuit 12 according to the supply voltage.

The proposed detector can be manufactured using elements that are serially produced in the industry, and is characterized by higher reliability in comparison with known similar detectors.

Claims (1)

The formula of the invention Kk A smoke fire detector containing an element of one-way conduction, the input of which is connected to the first terminal for connection to the fire alarm loop, and the output is connected to the first terminal of the electric power supply of the smoke detection signal generator and the input of the current limiting element, the output of which is connected to the first the output of the capacitor, the second output of which is connected to the common bus, with the second (2,0) C5 terminal for connecting to the fire alarm loop and to the second output of the power supply of the generator of the smoke detection signal, the output of which is connected to the indicator, and the input is connected to the output binary counter, to the C-input of this counter and to the first input of the clock generator, the first output of which is connected to the M-input of the binary counter and the first input of the comparison circuit, the output of which is connected to the K-input of the binary counter, the second input of the comparison circuit is connected to output of the amplifier, and the third input - to the output of the circuit "reset by the supply voltage, to the inputs of the amplifier connect a photodiode optically connected through a camera with light-absorbing walls to an infrared emitter connected to the output of a current switch, the first power output of which is connected to the first output of a capacitor and the input of an integrator, the output of which is connected to the first power output of an amplifier , the second power output of which is connected to the second power output of the current switch and the common bus, which differs in that the detector additionally contains a high-pass filter, the output of which is connected to the input of the current switch, and the input is connected to the second output of the clock generator, the second input which is connected to the output of the power reset circuit, the power terminals of which are connected to the corresponding power terminals of the amplifier, clock generator, binary salt counter and comparison circuit. (ee) at 50 what F) name) 60 b5