JPS58108439A - Photo pulse system smoke sensor - Google Patents

Abstract

PURPOSE:To provide a smoke sensor which reduces a power consumption and can make a maximum utilization of information during no production of any photo pulse, by a method wherein, when an output theory of a collecting amplifier, except a projecting time, is ''1'', a gate circuit, through which the collecting amplifier and a processing circuit are connected together, is adapted to close. CONSTITUTION:A luminous diode 2 is caused to emit light by means of an output of a pulse oscillator 1, and an output of a photoelectric converting element 3 is amplified by a collecting amplifier 4 to input it to an output deciding circuit 5 of the amplifier 4. At a normal time when smoke is absent at an optical path between the luminous diode 2 and the photoelectric converting element 3, the output the amplifier 4 produces a pulse of more than a specified value, a deciding circuit decides the absence of smoke from a pulse value, and if the output pulse of the amplifier 4 reduces to lower than the specified value due to smoke in the optical path, and deciding circuit decides the pressure of smoke and outputs a fire sensing signal. The output of the amplifier 4 is higher than 3V irrespective of the presence of smoke, and an input theory of a current exclusive- OR circuit 6 is set to ''1''. Thus, the output of the exclusive-OR circuit 6 is brought to a theory ''1'', a reverse voltage is applied to a diode 7 to bring it into OFF. That is, the output pulse of the amplifier 4 is inputted to the deciding circuit 5 to compare it with a comparison voltage, and this enables deciding of the presence of smoke.

Description

[Detailed description of the invention] The present invention relates to a light pulse type smoke detector.

In conventional smoke detectors of this type, the light source of a dimming type or scattered light type smoke detector is made to emit light in a pulsed manner to reduce the amount of stain power consumed. On the light-receiving side, the output of the light-receiving amplifier is input to the determination circuit in synchronization with the light emission of the light projector, and the output of the light-receiving amplifier is not input to the determination circuit during the period when the light projector does not emit light. For this synchronization, it is common to insert a resistor in series with the light emitting element on the emitter side and send the voltage across this resistor to the receiver side, but in such a case, heat loss due to the resistor is The disadvantage is that this occurs. In addition, on the receiver side, the output of the receiver amplifier is grounded with a diode except when the emitter is emitting light, so that the output of the receiver amplifier is not given to the determination circuit, so for most of the period (pulse During this period, the output of the light receiving amplifier is grounded, which not only wastes power, but also makes it impossible to use the db optical information during this period. Ideally, the received light output when there is no optical pulse is zero, but generally some kind of interfering light is received. This interference light includes light that enters regularly from the outside and light that enters sporadically. The former is the reception of sunlight or indoor light scattered by dust in the air, etc., and changes slowly over time. The latter is caused by, for example, irradiation from a car headlight or a flash from a lightning strike, and is incidental and has a large value. It seems that there is no problem because it is completely blocked when there is no pulse, but these interfering lights are mixed in even when there is a pulse. Therefore, there is a risk of erroneous determination due to interference light. However, since conventional pulse-type smoke detectors block all of this information, there is no means to correct the light reception output during pulses.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light pulse type smoke detector that solves the above-mentioned conventional drawbacks, consumes less power, and can make maximum use of information during periods when there is no light pulse. It is in.

The sensor of the present invention includes a light emitter that generates light pulses with a constant period, a light receiver that receives the light emitted directly from the light emitter or light scattered by smoke, and a light receiving amplifier that amplifies the electrical output of the light receiver. and a processing circuit that determines the presence or absence of smoke by comparing the output voltage of the light receiving amplifier with a comparison voltage. When the output of the gate circuit connecting the processing circuit and the light receiving amplifier is above a certain level, logic@
1'', and the gate circuit is closed when the output logic of the light receiving amplifier is @1'' at times other than when the light projector is projecting light.

Note that by varying the comparison voltage of the determination circuit using a voltage obtained by delaying the output of the light receiving amplifier with a delay circuit, it is possible to obtain a determination result that is corrected depending on the level of interfering light when there is no pulse.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows that the present invention is applied to a dimming type smoke detector, and a light-emitting diode (light emitter) 2 is caused to emit light by the output of a nine-wave detector l.
The output of the photoelectric conversion element (light receiver) 8 is amplified by the light receiving amplifier 4, and the output of the amplifier 4 is input to the determination circuit 5 through a resistor and a capacitor. In normal times when there is no smoke in the optical path between the light emitting diode 2 and the photoelectric conversion element 80, the output of the amplifier 4 is a pulse of a certain value or more.The judgment circuit judges that there is smoke and outputs a fire detection signal. do.

Note that since no series resistance is connected to the light emitting diode 2, there is no resistance loss. When the oscillator 1 does not output a pulse and therefore the light emitting diode 2 does not emit light (no pulse), the oscillator 10P terminal (positive output terminal P
A high level is sent out from the inverted voltage of 1) and input to one side of the exclusive OR circuit 6. The output of the light receiving amplifier 4 is connected to the other input of the exclusive OR circuit 6. The output of the exclusive OR circuit 6 is connected to the input of the determination circuit 6 via a diode 7. Therefore, at the time of pulse, the P terminal of the oscillator 1 is at a low level, so one input logic of the exclusive OR circuit 6 is 10''.The output of the amplifier 4 is at least, for example, 8V or higher (regardless of smoke or non-smoke). At this time, it is assumed that the input logic of the exclusive OR circuit 60 is 11''. Therefore,
Now, the output of the exclusive OR circuit 6 is at logic "'1" (high level), and a reverse voltage is applied to the diode 7 to turn it off. That is, the output pulse of the amplifier 4 is inputted to the determination circuit 5 through a resistor and a capacitor, and is compared with the comparison voltage as described above to determine the presence or absence of smoke. When there is no pulse, the P terminal of the oscillator 1 is at a high level, and one input logic of the exclusive OR circuit 6 is @1'''.At this time, if, for example, the receiver 8 receives a flash of lightning, When the output voltage of the amplifier 4 becomes, for example, 8V or more, the other input logic of the exclusive OR circuit 6 also becomes 11''. Therefore, when the output of the exclusive OR circuit 6 is not at a low level, the diode 7 is made conductive, so that the input of the determination circuit 50 is grounded. That is, the lightning flash output is not input to the determination circuit 5. In this embodiment, the diode 7 and the output of the exclusive OR circuit 6 constitute a gate circuit. The exclusive logic circuit 6 is a logic circuit that outputs "1" when the output of the light receiving amplifier 4 is above a certain level. In this embodiment, as described above, erroneous determination is prevented by blocking lightning flashes and the like. However, even when there is no pulse, when the output of the light receiving amplifier 4 is below a certain level (for example, 8V or below), the output of the exclusive OR circuit 6 is at a high level, and the gate circuit is in an open state. It is. Therefore, since the stationary noise light is not blocked, it is possible to correct the amount of light received during pulses by the amplified output of the stationary noise light. Moreover, it is also possible to discover a malfunction of the device by monitoring the noise light during steady state.

FIG. 2 is a circuit diagram showing an example of the determination circuit 5. As shown in FIG. That is, the input voltage is input to one terminal of the comparison circuit 8, and the comparison voltage VR is input to the ten terminal of the comparison circuit 8. On the other hand, a voltage obtained by delaying the input voltage by a delay circuit τ is applied in series to the comparison voltage VR. Comparison circuit 8 operates for comparison only during pulses, and outputs a high level when the voltage at one terminal is lower than the voltage at terminal 10, but at this time, the delayed output voltage at terminal 10 when there is no pulse is compared. It is added to the voltage VR and input. Therefore, for example, when a large amount of scattered light from the sun is received during the day, the comparison voltage will be high and the smokeless determination value will also be high. Even though the light emitted from the projector itself is dimmed and received, the overall amount of light received increases due to the received scattered light from the sun, which prevents it from being mistakenly judged as smokeless. be.

FIG. 8 shows an embodiment in which the present invention is applied to a scattered light type smoke detector. That is, the emitter 2 emits a light pulse in response to the output pulse of the oscillator l, and the receiver 8 receives the direct light from the emitter 2. It is arranged at a position where it does not receive light but receives scattered light due to smoke. Of course the sun ka, ka1. Yu-■Kyogawa,i,,8
．． On the other hand, when there is no smoke when one light is being received, the light receiver 8 does not receive the output light from the light emitter 2, so the output of the amplifier 4 is a low voltage due to noise light. When there is smoke, the output light from the projector 2 is scattered by smoke, received by the light receiver 8, and amplified by the amplifier 4.

During the pulse, the output value of the oscillator 1 is at a high level, and the output of the OR circuit 9 is also at a high level.Since a reverse voltage is applied to the diode 7, the diode 7 is in an off state, and the output of the amplifier 4 is The signal is input to the judgment circuit 1o through a resistor and a capacitor. The determination circuit 10 compares the input pulse with a constant value to determine the presence or absence of smoke. Amplifier 4 when there is no pulse
The output voltage of the inverter 11 is a low voltage, e.g., 8V or less, due to steady noise light, and is below the logic @1'' level of the inverter 11. Therefore, the output of the inverter 11 is a logic @1' level.
In addition, since a reverse voltage is applied to the diode 7 via the OR circuit 9, the diode 7 is in an off state, and the output of the amplifier 4 is input to the determination circuit 10 via the resistor and capacitor. Therefore, the determination circuit 10 can correct the determination value during pulses based on the noise light level during non-pulse times. However, when the receiver 8 outputs an output due to a lightning flash, for example, the amplifier 4 outputs 8V or more, so the input logic of the inverter 110 becomes "11", and the output logic of the inverter 11 becomes "0". The output becomes low level, the diode 7 becomes conductive, and the input of the judgment circuit 10 is grounded.Therefore, a single disturbance light such as a lightning flash will not be input to the judgment circuit.In this case, the judgment circuit 1
0 does not need to operate in synchronization with the pulse, and may simply be output when the input voltage exceeds a certain comparison value. Note that the above-mentioned constant comparison value can be corrected by the steady noise light level as described above. In this case, inverter 11. The OR circuit 9 and the like constitute a logic circuit, and the output of the logic circuit and the diode 7 constitute a gate circuit.

The gate circuit is a gate circuit that is closed when the output logic of the light receiving amplifier is 1'' at times other than when the light emitter emits light.

As described above, in the present invention, since no series resistor is connected to the projector, power is not wasted, and power consumption can be reduced. Furthermore, since the gate circuit is configured to be closed by an interfering sound caused by a flash of light or the like when there is no pulse, it is possible to prevent malfunctions caused by a single interfering light. Furthermore, since the configuration allows steady noise light below a certain level to pass through the gate circuit, it is possible to determine the presence or absence of smoke using a comparison voltage corrected by the steady noise light when there is no pulse. In other words, more accurate judgments can be made. There is an effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment in which the present invention is applied to a dimming type smoke detector, Fig. 2 is a circuit diagram showing an example of the determination circuit of the above embodiment, and Fig. 8 is a block diagram showing an example of the judgment circuit of the above embodiment. FIG. 3 is a block diagram showing another embodiment applied to a scattered light type smoke detector. In the figure, l: pulse oscillator, 2: floodlight,
8... Light receiver, 4... Light receiving amplifier, 5... Judgment circuit, 6... Exclusive OR circuit, 7... Diode.
8... Comparison circuit, 9... OR circuit, 10... Judgment circuit, 11... Inverter, τ... Delay circuit, VR
...Comparison voltage. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) a light projector that generates light pulses with a constant period; a light receiver that receives the light emitted directly from the cough projector or the light scattered by smoke; and a light receiving amplifier that amplifies the electrical output of the light receiving section;
A dimming type or scattered light type light pulse type smoke sensor comprising a processing circuit that determines the presence or absence of smoke by comparing the output voltage of the light receiving amplifier with a comparison voltage, wherein the light receiving amplifier and the processing circuit are provided. and a logic circuit that makes the output of the light-receiving amplifier logic @1" when the output of the light-receiving amplifier is above a certain level, the output of the light-receiving amplifier is A light pulse type smoke detector characterized in that the gate circuit is closed when the logic is "1". (2) The optical pulse type smoke detector according to claim 1, further comprising a delay circuit that delays the output of the light receiving amplifier, and the comparison voltage of the processing circuit is variable according to the output voltage of the delay circuit. Something that is characterized by: