SU1418784A2 - Smoke alarm - Google Patents

Abstract

The invention relates to an automatic alarm system and can be used to detect the presence of suspended particles (smoke, dust, fog) in the environment, to automatically turn on actuators, for example, in chemical, coal, textile industry facilities. The aim of the invention is to improve the noise immunity of the smoke alarm. For this purpose, the EXCLUSIVE OR element 32 and the one-oscillator 33 are introduced into the proposed detector, and the element And 5 is provided with a third input. In this case, the first and second inputs of the AND element are connected respectively to the first and second inputs of the EXCLUSIVE OR element, the output of which is connected to the one-shot input. The third input element And is connected to the output of the one-shot. At any discrepancy in time of the leading edge of one of the pulses at the first and second inputs of element 5, the output signal of the EXCLUSIVE OR element 32 appears and the one-shot 33 is triggered, the output of which inhibits the signal from AND 5, i.e. smoke weighting, the actor does not generate a false output signal when a constant output signal appears from amplifier 3 due to its malfunction, as well as under the influence of industrial noise. 6 Il. $ | SL

Description

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I The invention relates to an automatic (fire alarm) and is an improvement of the smoke detector ho auth. St. No. 1200313.

 The purpose of the invention is to increase the noise immunity of the smoke detector.

FIG. 1 shows the flow chart of the proposed smoke story, atel; in fig. 2 - a schematic diagram of the Element AND-NOT node of the front of the pulse; in fig. 3-6 - timing diagrams, as discussed, the work of the proposed | smoke exhaust, atel.

 The proposed smoke detector contains a radiator 1, a radiation receiver 2, an amplifier 3, a generator of 4 pulses, an AND 5 element, a pulsed relay 6 made with transistors 7 and 8, a resistor 9 and 10 and a condenser 11, - 1 element 12, made on reactor 13 and capacitor 14, element iHE 15, key element 16, comparator 17, source 18 of reference voltage, | node 19 of pulse-edge delay, made on capacitor 20, diode 21 element HE 22 and element AND-NO 23, made on the diodes 24-27, resistors 28-30 and transistor 31. In addition, the detector with contains the element EXCLUSIVE OR 32, the one-shot 33, the element And 5 is provided with a third input, while the first and second inputs of the element And 5 are connected respectively to the first and second inputs of the element EXCLUSIVE OR 32, the output of which is connected to the input of the one-shot 33, the third input of the element And 5 connected to the output of the one-shot 33.

The EXCLUSIVE OR 32 element generates the output signal only if there is 1 signal on one of its inputs and will not generate an output signal if there are: or no signals on both of its inputs.

The one-vibration 33 when the signal at its input (the falling front) disappears, forms the output signal (logical “O) of a given duration.

The smoke detector works as follows.

The radiation receiver 2 is located at an angle to the radiator 1 in such a way that its direct radiation does not fall on the radiation receiver 2, therefore, in the absence of smoke, there are no output signals from the radiation receiver 2, amplifier 3, element 5, pulse relay 6, comparator 17, and the capacitor 14 of the integrating element 12 (closed) is discharged by the key element 16, the input of which is the output signal of the element NOT 15. When smoke appears, radiation pulses from the radiator 1 reflected from the smoke particles affect the radiation receiver 2 electrically whose signal is

amplified by amplifier 3, the output of which produces amplitude-normalized pulses, the leading edge of which appears to be delayed by time relative to the pulse of generator 4 due to 5 inertia of emitter 1, receiver 2 of radiation and amplifier 3, from whose output the pulses arrive at the second input of element I five.

Simultaneously with the arrival of a pulse (signal QA logic лог 1) from the generator 4 to the emitter 1, the pulse arrives at the input of the node 19 of the pulse-front delay. In this case, the diodes 21 and 24 (Fig. 2) are closed with and the current flowing through the resistor 28 charges the capacitor 20 to the voltage,

5 at which the diodes 26 and 27 and the transistor 31 are opened, the switching element is NOT 22. At the output of the node 19, the leading edge of the pulse appears, which is delayed by the time r3 relative to the pulse of the generator 4. At the end of the pulse of the generator 4 (logical signal "O") 26 and 27 are closed, the capacitor 20 is discharged through diode 2 and at the output of the node 19 a rising edge of the pulse is formed, which coincides in time with the rear

5, the pulse front of the generator 4, i.e., at the output of the node 19, are received at the first input of the element 5, pulses whose duration is shorter than the duration of the pulses of the generator 4 by the delay time T3, determined by the values of the resistance of the resistor 28 and the capacitor 20.

Thus, with the appearance of smoke in the receiving chamber of the weigher, the front and rear edges of the pulses at the first input of the element And 5 (Fig. 3a) coincide in

5 times with the leading and falling edges of the pulses at the second input of the AND 5 element (Fig. 36), at the same time both inputs of the EXCLUSIVE OR 32 element are filled, the output signal of which is absent

Q (fig. Sv), while the one-shot 33 is in the initial state and its output signal (logical "1) is fed to the third input of the AND 5 element (fig. 3g).

Since all the inputs of the element And 5 are filled, its output pulses (Fig. A)

5 is fed to the input of a pulse relay 6, at the output of which a constant voltage is generated.

The formation of a constant voltage at the output of the pulse relay 6 (Fig. 1) is ensured by the fact that in the presence of the output pulse of the element And 5 the transistor 8 of the pulse relay 6 is opened by the base current through the resistor 10 and the open transistor 7, the shunt capacitor 11, and during pause at the output element And 5 transistor 7 is closed, and

 the transistor 8 is open by the charge current of the capacitor 11 flowing through the resistor

10 and the base-to-emitter transition of the transistor 8. Thus, the pulse relay 6 provides for a delay in the output signal for a time longer than the repetition period of the output pulses of the AND 5 element.

When the output voltage of the impulse relay 6 appears, the output signal of the HE element 15 disappears and the key element 16 opens, the output voltage of the pulse relay 6 being integrated by the integrating element 12. The output voltage of the integrating element also increases during a predetermined time interval. reaches the threshold level of the comparator 17, which forms the smoke signal output signal.

When a constant output signal of amplifier 3 appears (Fig. 46) due to a malfunction of its electric elements, at the output of the EXCLUSIVE OR 32 element a signal appears (Fig. 4c) that occurs during the operation of the pulses (Fig. 4a) at the first input of the element I 5, with the falling edge of the output pulses of the element EXCLUSIVE OR 32 (Fig. 4c), a one-shot 33 is triggered, the output of which produces a signal (logical "O) of a given duration t (Fig. 4d), which goes to the third the input element is And 5. If there is a signal (logical “1) on the first OM (Fig. 4a) and the second (Fig. 46) input element And 5 there is no signal at its third input (Fig. 4c) and there is no output signal (Fig. 4e) element AND 5, therefore the false output signal of the smoke detector l is missing.

Under the influence of industrial noise, short pulses (fig; 56) may appear at the output of amplifier 3, coinciding in time with pulses (Fig. 5a) at the first input of the AND 5 element, and a signal appears at the output of the EXCLUSIVE OR (Fig. 5c), which disappears during the action of pulses (Fig. 56) at the output of amplifier 3, while a one-shot 33 is triggered on the falling edge of the output pulses of the EXCLUSIVE OR 32 element (Fig. 5c), the output of which is a signal (logical "O) given the duration of t (Fig. 5d), which enters the third input element And 5. If there is a signal on the first (Fig. 5a) and second (Fig. 56) inputs of the And 5 element, there is no signal at its third input (Fig. 5d) and there is no output signal (Fig. 5e) of the And 5 element, therefore, there is no false smoke detector output. .

Under the influence of industrial noise at the output of the amplifier 3 may appear

pulses (Fig. 66), overlapping in time pulses (Fig. ba) on the initial input of the element AND 5, while the output of the EXCLUSIVE OR 32 element is a signal (Fig. 6c), which disappears during the action of the pulses ( 4a) (fig. ba) at the first input of the element And 5, while on the falling edge of the output pulses of the element EXCLUSIVE OR 32 (fig. 6c) a one-shot 33 is triggered, the output of which generates a signal (logical "O) of the specified duration t (Fig. 6d), which is fed to the third input of the element And 5. If there is a signal (logical "1) on the first (phi The ba and the second (Fig. 66) inputs of the And 5 element are missing at its third input (Fig. 6c) and there is no output signal (Fig. 6e) of the And 5 element, therefore there is no false output from the smoke detector.

For normal operation of the device, the duration t of the output pulse of the one-oscillator 33 must be equal to or longer than the duration of the pulses at the first input of the element And 5.

With prolonged exposure to noise at the output of amplifier 3, a pulse sequence appears, in which the leading edge of at least one of the pulses does not coincide with the leading edge of the output pulse of node 19 of the pulse front delay, and the output signal of the pulse relay 6 disappears. The output signal of the element is NOT 15 and the key element 16 is closed, the discharge, the capacitor 14 of the integrating element 12, the output voltage of which disappears before reaching the threshold level of the comparator 17, therefore the false output Smoke detector signal is absent.

The proposed smoke detector generates an output signal only under the condition of multiple coincidence in time of the leading edges of the pulses at the first and second inputs of the AND 5 element, which is possible only with the appearance of smoke in the receiving chamber of the smoke detector. The duration of the leading edges of the pulses at the inputs of the element And 5 is a fraction of a microsecond, therefore the probability of multiple coincidence in time of the leading edges of the pulses due to the random nature of the interference from amplifier 3 is negligible, which increases the noise immunity of the smoke detector.

Claims (1)

Invention Form Smoke Detector according to ed. St. D | 9 1200313, characterized in that, in order to increase the noise immunity of the detector. an EXCLUSIVE OR element and a one-shot are entered into it, the output of the pulse-front delay node and the amplifier output are connected respectively to the first and the second inputs of the EXCLUSIVE OR element, the output of which is connected to the input of a one-shot, the output of which is connected to the third input of the element I. FIG. 6