JPS6332691A - Photoelectric type analog smoke sensor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to improvements in photoelectric analog embedded sensors.

[Background technology]

As shown in Fig. 4, the photoelectric analog embedded sensor has a chamber C with a labyrinth structure, and a light-emitting chamber A and a light-receiving chamber B.
The light-receiving chamber B is placed in a position where it does not directly receive the light emitted from the light-emitting chamber A, and the light-receiving chamber B detects the scattered light caused by the smoke that has entered the chamber C to obtain a signal according to the smoke concentration. It has a structure. Note that in the figure, the shaded area indicates the sensing area.

FIG. 5 is an electric circuit diagram showing the basic configuration of a photoelectric analog smoke detector, in which a light emitting element drive circuit 1 is installed in a light emitting chamber A to cause a light emitting element 10 such as an LED to emit light intermittently. In the other light-receiving chamber B, there is provided a light-receiving signal amplification circuit 2 provided with a light-receiving element 20 such as a photodiode.

The light scattered by the smoke in the chamber C is detected by the light receiving element 20.
When detected, it is photoelectrically converted into a level signal according to the smoke concentration in the light reception signal amplification circuit 2 and then amplified.The output integrated in the integration circuit 3 is amplified in the DC amplification circuit 4 and sent to the fire alarm system. The analog signal VouT with the output characteristics required by the side is obtained.

By the way, in such a photoelectric analog smoke detector, the solid line in Figures 6 and 7 (Figure 6 shows the output V of the integrating circuit)
Figure 7 shows the output characteristics of smoke density and analog output Vo.However, due to deterioration of the optical system, etc. When the output decreases, the output characteristic becomes approximately like a broken line.

For example, in an actual smoke detector, in the initial characteristics without deterioration of the optical system, when the smoke concentration is 0.57 m, the peak value v3 of the pulse voltage is 0.2 V, and the analog output Vo is IV
, when the smoke density is 20%/m, VS is 1.6 V and the analog output Vo is 5 V. 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. IV, 7f log output Vo is 0.75V, smoke density 2
When 0%/m, Vs is 0. 8V, 7 analog output vO
voltage drops to 2.7v.

In this way, in an actual smoke detector, the sensitivity is 1/2
Analog output Vo when the smoke density is θ%/m even if it drops to
The value of Vo decreases only to IV-0.75V. Therefore, the analog output Vo of the smoke detector at a smoke density of 0%/m
If the variation width is specified to be around ±0.3V,
On the receiver side, there is an inconvenience that it is not possible to judge the output of the smoke detector and determine that the sensitivity has decreased.

[Purpose of the invention]

The present invention has been made in view of the circumstances surrounding ridges, 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 abnormalities when sensitivity decreases.

[Disclosure of the invention]

The present invention proposed to achieve the above object includes a comparison circuit section that compares the output level of the integrating circuit with a preset reference level signal, and when the output of the integrating circuit becomes lower than the reference level, The present invention is characterized by a configuration in which the analog output of the DC amplifier circuit is reduced to 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 sensor of the present invention, and l is a light emitting element drive circuit, which drives the light emitting element 10 (emits light) at a predetermined period.

2 is a light emitting element lO emitted by the light emitting element drive circuit 1;
This is a light receiving and amplifying circuit that receives light scattered by smoke and amplifies the received light signal.The signal that has been photoelectrically converted by this light receiving and amplifying circuit 2 is guided to an 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
Switching means such as FETs are turned on and off to charge the integrating capacitor.

The output of the integrating circuit 3 is led to a DC amplifier circuit 4, where it is converted into an analog signal v with characteristics required by the fire alarm system.
O is output.

Reference numeral 5 denotes a comparator circuit section which constitutes a main part of the present invention, and an integrator circuit 3
A signal obtained by further amplifying the output of
The output level is set according to the output level when the output is reduced by approximately half.

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

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 the transistor TR.

According to this configuration, when there is no abnormality in the optical system and there is no decrease in the output of Vs, the output of the operational amplifier OP of the comparator circuit section 5 is at the rHJ level, and the diode D becomes non-conductive, so that the final amplifier stage The reference voltage vb of the operational amplifier OP3 does not change, and the DC amplifier circuit 4 outputs an analog signal V according to the smoke density.

Output.

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 comparison circuit section 5 becomes rLJ level, and the diode D is made conductive, causing the operational amplifier of the final amplification stage to Since the reference voltage vb of OP3 is lowered and its output is inverted to the rLJ level, the transistor TR is canted off and the output Vo is reduced to approximately zero level. 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 the comparison circuit section 5
The configuration is such that Vs is input to the inverting input terminal of the operational amplifier OP that constitutes the operational amplifier OP, and the base at voltage ■Ref is input to the non-inverting input terminal. ), a resistor R is connected to the second stage operational amplifier O of the DC amplifier circuit 4.
Connected to the output terminal of P2.

If an abnormality occurs in the optical system and Vs falls below VRef,
The output of the operational amplifier OP becomes rHJ level, which lowers the inverted input signal of the final stage operational amplifier OP3 of the DC amplifier circuit 4 (the base t[voltage vb does not change), so the output of the operational amplifier OP3 is inverted to the "H" level. The transistor TR is made conductive to lower the output Vo to approximately zero level.

In the above embodiments, 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, making it easy for the receiver to identify an abnormality, making it possible to use photoelectric analog smoke detectors with high reliability. 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. Figure 4 is a side view of the configuration of a photoelectric analog smoke detector, Figure 5 is its basic electrical configuration diagram, and Figure 6 is a diagram showing the relationship between the output of the integrating circuit and the analog output. Characteristic diagram showing the relationship,
FIG. 7 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... Comparison circuit section

Claims (1)

[Claims] a light-emitting element drive circuit that causes the light-emitting element to emit light intermittently; a light-receiving signal amplification circuit that detects light scattered by smoke from the light-emitting pulse of the light-emitting element with a light-receiving element and outputs an electrical signal at a level corresponding to the smoke density; A received light signal amplification circuit that outputs this received light signal, an integrator circuit that integrates the output pulse from this received light signal amplification circuit, and a DC amplification circuit that amplifies the output of this integrator circuit into an analog signal with predetermined output characteristics. A photoelectric analog smoke detector is equipped with a comparison circuit that compares the output level of the integrating circuit with a signal at a preset reference level, and when the output of the integrating circuit falls below the reference level, the output level of the DC amplifier circuit is A photoelectric analog smoke detector characterized by having a configuration that reduces analog output to approximately zero level.