JPH0439718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to improvements in photoelectric analog smoke detectors.

[Background Art] As shown in FIG. 4, a photoelectric analog smoke detector is provided with a light emitting chamber A and a light receiving chamber B in a chamber C having a maze structure, and the light receiving chamber B is connected to the light emitting chamber A. It is placed in a position that does not directly receive the emitted light, and the scattered light from smoke that has entered chamber C is transmitted to light receiving chamber B.
The structure is such that a signal is detected according to the smoke concentration. Note that in the figure, the shaded area indicates the sensing area.

Figure 5 is an electrical circuit diagram showing the basic configuration of a photoelectric analog smoke detector.
A light emitting element drive circuit 1 for causing a light emitting element 10 such as an LED to emit light intermittently is provided, and in the other light receiving chamber B, a light receiving signal amplifying circuit 2 provided with a light receiving element 20 such as a photodiode is provided.

When the light scattered by smoke in the chamber C is detected by the light receiving element 20, it is photoelectrically converted into a level signal according to the smoke concentration in the light receiving signal amplification circuit 2, and then amplified, and the integrated output in the integrating circuit 3 is as follows. It is amplified in the DC amplifier circuit 4 to obtain an analog signal VouT having output characteristics required by the fire alarm system.

By the way, in such a photoelectric analog smoke detector, the solid lines in Figures 6 and 7 (Figure 6 shows the relationship between the output Vs of the integrating circuit and the analog output Vo, and Figure 7 shows the relationship between the smoke density and the analog output Vo) Although smoke density output characteristics as shown in (showing output characteristics) are obtained, if the output of the light emitting element 10 decreases due to deterioration of the optical system or the like, the output characteristics become approximately as shown by the broken line.

For example, in an actual smoke detector, in the initial characteristics without optical system deterioration, the smoke density is 0%/
m, the peak value of the pulse voltage Vs is 0.2V, the analog output Vo is 1V, and when the smoke density is 20%/m, Vs is
1.6V, analog output Vo is 5V, when the output of the light emitting element decreases, when the smoke density is 0%/m, the peak value of the pulse voltage Vs is 0.1V, the analog output Vo is 0.75V, and the smoke density At 20%/m, Vs is 0.8V,
Analog output Vo drops to 2.7V.

In this way, in an actual smoke detector, even if the sensitivity decreases to 1/2, the value of the analog output Vo when the smoke density is 0%/m only decreases from 1V to 0.75V. For this reason, if the variation width of the analog output Vo of a smoke detector at a smoke density of 0%/m is specified to be around ±0.3V, the receiver side will judge the output of the smoke detector and the sensitivity will decrease. This may cause inconveniences such as not being able to determine what has happened.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric analog smoke detector that has a simple configuration and is capable of determining an abnormality when sensitivity decreases.

[Disclosure of the invention]

The present invention proposed to achieve the above object includes a comparison circuit unit that compares the output level of the integrator circuit with a reference level signal set in advance to determine a sensitivity reduction abnormality, and the output level of the integrator circuit is When is above the reference level, the analog signal output from the DC amplifier circuit is output as is to the fire receiver side, while when the output of the integrating circuit falls below the reference level, the analog signal output from the DC amplifier circuit is output as is. The structure is such that the signal is output to the fire receiver as a sensitivity reduction abnormal signal that is lowered to and maintained at approximately zero level.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of an analog smoke detector of the present invention, in which 1 is a light emitting element drive circuit;
The light emitting element 10 is driven (emits light) at a predetermined period.
2 receives light scattered by smoke from the light emitting element 10 emitted by the light emitting element driving circuit 1 with a light receiving element 20;
The light receiving signal amplifying circuit 2 amplifies the light receiving signal, and the signal photoelectrically converted by the light receiving signal amplifying circuit 2 is guided to the integrating circuit 3.

The integrating circuit 3 receives a timing pulse synchronized with the light emission timing of the light emitting element 10 from the light emitting element drive circuit 1, and operates a switching means such as an FET.
Turn it ON and OFF to charge the integrating capacitor. The output of the integrating circuit 3 is led to a DC amplifier circuit 4, where an analog signal Vo having characteristics required by the fire alarm system is output.

Reference numeral 5 denotes a comparator circuit section which is an important part of the present invention, and the signal obtained by further amplifying the output of the integrating circuit 3 in the first stage of the DC amplifier circuit 4 is used as Vs to calculate the sensitivity caused by deterioration or dirt in the optical system. It is compared with a preset reference signal VRef to determine the abnormality of the drop.
This reference voltage VRef is set, for example, in accordance with the output level value when the output of the light emitting element 10 is approximately halved.

The comparison circuit section 5 connects a diode D (its cathode side is connected to the output end of the operational amplifier OP) and a resistor R to the output of the operational amplifier OP, and connects the other end of the resistor R to the final amplification stage of the DC amplifier circuit 4. It is connected to the non-inverting input terminal of the operational amplifier OP3 that constitutes the

The base of a transistor TR is connected to the output terminal of the operational amplifier OP3 in the final amplification stage, and an analog output Vo is obtained from both ends of a resistor RE provided on the emitter side of this transistor TR.

With this configuration, there is no abnormality in the optical system.
When the output of Vs is normal and there is no drop in the output, the output of the operational amplifier OP of the comparator circuit section 5 is at "H" level.
Since the diode D becomes non-conductive, the reference voltage Vb of the operational amplifier OP3 in the final amplifier stage does not change, and the DC amplifier circuit 4 outputs an analog signal V0 according to the smoke density.
Output as is to the fire receiver.

However, if an abnormality occurs in the optical system and the output of Vs decreases, and Vs becomes lower than VRef, the output of the operational amplifier OP of the comparator circuit section 5 becomes "L" level.
The diode D is made conductive to lower the reference voltage Vb of the operational amplifier OP3 in the final amplification stage, and its output is inverted to the "L" level, so the transistor
TR is cut off, the output V0 drops to almost zero level, and a sensitivity reduction abnormal signal is output to the fire receiver. It should be noted that the term "approximately zero level" here means a decrease in the output that can be sufficiently determined when the variation width of the analog output is taken into consideration, and does not necessarily have to be 0.

Since this output is held while the optical system is abnormal and the output is reduced, the receiver side immediately identifies it and determines that it is abnormal.

FIG. 3 is an output characteristic diagram of the analog smoke sensor, where A shows the initial characteristic and B shows the output characteristic of the analog smoke sensor of the present invention when the output decreases.

FIG. 2 is a block diagram of another example of the present invention, in which Vs is input to the inverting input terminal of the operational amplifier OP constituting the comparator circuit section 5, and the reference voltage is input to the non-inverting input terminal.
The configuration is such that VRef is input, and the output terminal of the operational amplifier OP is connected to a diode D (the anode is connected to the operational amplifier OP).
), a resistor R is connected to the output terminal of the second stage operational amplifier OP2 of the DC amplifier circuit 4.

When an abnormality occurs in the optical system and Vs falls below VRef, the output of the operational amplifier OP becomes "H" level,
The inverted input signal of the final stage operational amplifier OP3 of the DC amplifier circuit 4 is increased. (The reference voltage Vb does not change), so the output of the operational amplifier OP3 is inverted to the "L" level, the transistor TR is cut off, and the output Vo is reduced to approximately zero level.

In the above embodiment, the output of the integrating circuit is amplified to a predetermined level by the first stage amplifying section of the DC amplifier circuit as Vs, but as originally meant, it is the direct output from the integrating circuit. may be taken as Vs, and the output of the integrating circuit in the present invention includes such a concept.

〔Effect of the invention〕

As can be understood from the above description, the photoelectric analog smoke detector of the present invention includes a comparison circuit section that compares the output level of the integrating circuit, which decreases when an abnormality occurs in the optical system, with a preset reference level. The structure is such that when the output level drops below the reference level, the analog output is reduced to almost zero level and held, so the receiver side can easily identify abnormalities, making it possible to use highly reliable photoelectric analog smoke detectors. can get.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of one embodiment of the photoelectric analog smoke detector of the present invention, Fig. 2 is a circuit diagram of another example, and Fig. 3 shows the output characteristics of the photoelectric analog smoke detector of the present invention. Diagram 4 to explain in comparison with initial characteristics
The figure shows an example of the configuration of a photoelectric analog smoke detector, Figure 5 is its basic electrical configuration, Figure 6 is a characteristic diagram showing the relationship between the output of the integrating circuit and the analog output, and Figure 7
The figure is an output characteristic diagram showing the relationship between smoke density and analog output. Explanation of symbols, 1...Light emitting element drive circuit, 10...
...Light emitting element, 2... Light receiving signal amplification circuit, 20...
Light receiving element, 3... Integrating circuit, 4... DC amplifier circuit, 5... Comparing circuit section.

Claims (1)

[Scope of Claims] 1. A light-emitting element drive circuit that causes a light-emitting element to emit light intermittently, and a light-receiving element detects light scattered by smoke from the light emitting pulse of the light-emitting element, and outputs an electrical signal at a level corresponding to the smoke density. a light receiving signal amplification circuit,
In a photoelectric analog smoke detector, the integrator circuit is comprised of an integrator circuit that integrates the output pulse from the received light signal amplification circuit, and a DC amplification circuit that amplifies the output of the integrator circuit into an analog signal with predetermined output characteristics. A comparison circuit section is provided to compare the output level of the integrator circuit with a reference level signal set in advance to determine a sensitivity reduction abnormality, and when the output of the integrating circuit is above the reference level, the analog signal output from the DC amplifier circuit is While the signal is output as is to the fire receiver, when the output of the integrating circuit drops below the reference level, the analog output from the DC amplifier circuit is lowered to almost zero level and maintained as a sensitivity loss abnormal signal, which is used to detect the fire. A photoelectric analog smoke detector characterized by having a configuration in which the output is output to the machine side.