JPS62224891A - Photoelectric type analog smoke sensor - Google Patents

Abstract

(57) [Summary] 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 a photoelectric analog smoke detector used in automatic fire alarm systems and the like.

[Background technology] A photoelectric smoke detector, which detects smoke by arranging a light-emitting element such as an LED and a light-receiving element such as a photodiode in a chamber and detecting smoke by receiving scattered light from smoke that has flowed into the chamber, is an automatic fire detector. It is widely used in alarm systems (hereinafter abbreviated as "self-fire alarm systems") and the like.

Among such smoke detectors, conventional photoelectric smoke detectors are of the so-called ON/OFF type, which send out a smoke detection signal when the output value of a light receiving element exceeds a certain threshold value. Recently, in order to detect fires early and improve reliability, intelligent self-fire alarm systems have been developed in which fire judgment is made on the receiver side, but such systems require information on smoke concentration. needs to be sent out from time to time.

In order to simplify the design of the system, such information is required to have a certain relationship to the smoke concentration required by the intelligent fire alarm system (for example, Y=A−x+B1, where A: constant, B: smoke concentration O It is desirable to have a sensor output when

Also, considering the condition in which the smoke detector is placed, false alarms or missed alarms may occur due to deterioration of the light emitting element, dirt on the light emitting element or light receiving element, or dirt entering the chamber. It is desired that detection be performed easily.

[Purpose of the Invention] The present invention has been made in view of the current situation, and its purpose is to obtain an output with a certain relationship to smoke density required in an intelligent fire alarm system. It is an object of the present invention to provide a photoelectric analog smoke sensor which can easily detect deterioration of a light emitting element, dirt on a light emitting element or a light receiving element, or intrusion of dust into a chamber based on its output.

[Disclosure of the Invention] In order to achieve the above object, the photoelectric analog smoke detector of the present invention uses a light receiving element to detect light scattered by smoke from luminescent pulses intermittently output from a light emitting element. In a photoelectric analog smoke detector configured to convert into an electrical signal and output an electrical signal according to smoke density,
A light-receiving signal amplification circuit that amplifies the electrical signal photoelectrically converted by the light-receiving element, an integrating circuit that integrates the output of the light-receiving signal amplifying circuit, a first amplifier circuit that amplifies the output voltage of the integrating circuit, and an output of the first amplifier circuit. a second amplifier circuit that inverts and amplifies the voltage based on a voltage value within the output voltage range; and a second amplifier circuit that inverts the output voltage of the second amplifier circuit based on the voltage value within the output voltage range. It is characterized in that it includes a third amplification circuit for amplification.

Embodiment An embodiment of the present invention is shown in FIG. In the figure, 2 is the L located inside the chamber 3 of the photoelectric analog smoke detector 1.
It is a light emitting element made up of an ED or the like, and 4 is a light receiving element made up of a photodiode or the like arranged in the chamber 3 as well. The light emitting element 2 is intermittently driven by a light emitting element driving circuit 5 to output a light emitting pulse, and the light receiving element 4 receives light scattered by smoke from the light emitting pulse and generates a light receiving signal. This signal is transmitted to the light receiving signal amplification circuit 6
The signal is amplified and sent to the integrating circuit 7.

In the case of such a photoelectric smoke detector, the light emission pulse output from the light emitting element 2 is reflected by the inner wall of the chamber 3 and received by the light receiving element 4, so even if the smoke concentration is 0, the light reception signal can be amplified. A certain voltage appears at the output of the circuit 6.

Therefore, the relationship between the smoke density X and the output voltage y of the integrating circuit 7 is generally Y: a-X + b
(Equation 1) (Here, a is a constant, and b is the output voltage of the integrating circuit 7 when the smoke density is 0.) The relationship is as shown in (Equation 1). It becomes unique.

However, when designing an actual intelligent fire alarm system, the relationship between smoke concentration X and output voltage Y of smoke detector 1 is required to be different from the above (Equation 1), and this The relationship is generally expressed by the following (Equation 2).

Y=A-x+B (Equation 2) (Here, A is a constant, B is the output voltage of the smoke detector 1 when the smoke is 1 degree O, and AlB is an arbitrary value determined by the system being designed.) Therefore, the relationship in (Formula 2) cannot be obtained by simply amplifying (Formula 1). For this reason, in the present invention, the output of the integrating circuit is amplified by the first amplifier circuit, and then inverted and amplified by the second and third amplifier circuits 1 and 2 to obtain the desired output. There is.

The amplifier circuits I to m are composed of operational amplifiers 11 to 13, and the resistors R1 to R11 are connected as shown in the figure, so the amplification degrees A1 to A3 of each of the amplifier circuits I to I are as follows.
A1=1+R3/R2, A2=R7/Re, A3=R1
Determined by 1/RIO.

The output y of the integrating circuit 7 is input to a first amplifier circuit, and is input to a non-inverting input terminal of an operational amplifier 11 via a resistor R1.

The output V1 of the amplifier circuit engineer is input to the second amplifier circuit H,
It is input to the inverting input terminal of the operational amplifier 12 via the resistor R6. The output V2 of the amplifier circuit (2) is further inputted via a resistor RIO to the inverting input terminal of the operational amplifier 13 constituting the third amplifier circuit. In addition, operational amplifier 12.13
The input voltage supplied to the non-inverting input terminal of
Indicated by 2. The output v3 of the amplifier circuit (2) thus obtained is sent to the receiver (not shown) of the intelligence fire alarm system as the output of the smoke detector 1 (Y in equation 2).

According to such a configuration, the following relational expression is established.

Vl = AI (a, x + b) (23)
A2 (Vl - VSI) = VSl - V2 (Formula 4) A3 (V2 - VS2) = VS2 - V3 (
Formula 5) When these formulas are rearranged, V 3 = A 1・A 2-A 3-a-x + A
1・A 2・A 3-b-A3 (1+A2)VS
1 + (1+A3)VS2 (2〇) is obtained.

Here, AI・A2−A3・a=A (Formula 7)
% formula %) Then, (2〇) becomes V 3 = A-x + B, and the analog signal output shown by (Equation 2) required by the fire alarm system is obtained, so the actual system design In doing so, each resistance value may be appropriately selected depending on A and H required by the system. Normally, the output V3 when the smoke density is 0 (x=O) is expressed as (28)B
It is.

A design example of the system according to the present invention will be explained in more detail using an example shown in FIGS. 2 and 3. Now, in this example, as shown in Figure 2, when smoke is 1 degree 0%/m, 100
Assume that a voltage of 700 mV is generated as the output y of the integrating circuit 7 when mV1 smoke density is 220 S%/m (i.e.,
y=2.87x+0.1). However, on the receiver side of the fire alarm system, as shown by the solid thick line in Figure 3, when the smoke density is 0%/m, the voltage of 5V is detected when the IV1 smoke density is 22.5%/m. Assuming that the output Y of the amplifier 1 is required (that is, Y=17.8x+1), if the resistors R2 and R3 of the first amplifier circuit I are set to, for example, 10Ω and 90Ω, then (
Amplification degree A1=10), the output v1 of the amplifier circuit becomes IV at 0%/7m and 7V at 22.5%/m, as shown by the solid thin line in FIG. In the second amplifier circuit H, resistors R6, R
7 are both LookΩ, the amplification degree A2=1), and the voltage VS1 of the non-inverting input terminal is 4V. Since the output V1 is input to the inverting input terminal, the output v of the amplifier circuit ■
2 is the inverted output V1 (dotted chain line in FIG. 3) with reference to the voltage VS 1 (=4V). Next, the third
The resistance RIO of the amplifier circuit ■ is set to 600Ω, and R11 is set to 40Ω.
0 to Ω, amplification degree A3 = 2/3), voltage VS2 to 3
．． Set it to 4V. Since the output V2 of the amplifier circuit ■ is input to the inverting input terminal, the output V3 of the amplifier circuit ■ (i.e., the output Y of the smoke detector 1) converts the output V2 into a voltage VS2 (=3
．． 4V) as a reference (solid thick line in Figure 3)
becomes. Therefore, the output Y of the smoke detector 1 will be as required by the system.

Next, we will consider the case where the light emitting element 2 deteriorates, the light emitting element 2 or the light receiving element 4 becomes dirty, or dust or the like enters the chamber 3 due to the output Y (VS) of the smoke detector 1 as described above. .

In this case, due to deterioration of the light emitting element 2 and dirt on the light emitting element 2 or the light receiving element 4, the output y of the integrating circuit 7 when the smoke density is 0 (x=O) becomes smaller than b, resulting in bl (bl<b). . By the way, the output V3 (=81) of smoke detector 1 at this time
it, in (formula 6), ite X: 0, b = bl, so VS (=81) = A1・A2・A3・b
l-A3 (1+A2)VS 1 + (1+A3)VS2. Therefore, the output V3 (=
81) is the output V3 (==
B) is smaller by AI・A2・A3 (bb-b 1). If you memorize the value of B when the smoke detector is normal on the receiver side, you can identify this change and detect abnormalities such as deterioration of the light-emitting element 2 or dirt on the light-emitting element 2 or the light-receiving element 4. can be detected.

Next, dust enters the chamber 3, and the smoke concentration is 0 (x=O
), the output y of the integrating circuit 7 becomes larger than b, and y=b
2 (b2>b). At this time, the output V3 (=82) of the smoke detector 1 is obtained by setting x=O1b=b2 in (Equation 6), so 'V3 (=82)=AI・A2・A3・b2− A3
(1+A2)VS 1 + (1+A3)VS2. Therefore, the output V3 (
=B2) is the output V3 (=
B) is larger by A1, A2, A3 (b2-b). By the way, the value of the output V3 increased due to dust remains constant over time, but the output V3 due to smoke changes greatly in a short period of time, so the receiver side can determine that the change in output is due to dust.

Incidentally, as the integrating circuit 7, a sample and hold circuit may be used instead of a normal integrating circuit. Also,
Although an example is shown in which an LED is used as the light emitting element, it goes without saying that it may also be an element using a laser beam.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, even if the output characteristics of the integrating circuit are different from those of a system such as an intelligent fire alarm system, the characteristics required by the system can be An analog output signal having a certain relationship with smoke concentration can now be obtained, and furthermore, it is possible to easily determine deterioration of the light-emitting element, dirt on the light-emitting element or light-receiving element, or intrusion of dust or the like into the chamber based on the output signal.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of an embodiment of the present invention, Fig. 2 is a graph showing an example of the relationship between the output of an integrating circuit and smoke density, and Fig. 3 is a graph showing an example of the relationship between the output of the smoke detector and smoke density according to the present invention. It is a graph showing an example of the relationship. 1... Photoelectric analog smoke detector, 2... Light emitting element,
3... Light receiving element, ■... First amplifier circuit, ■...
second amplifier circuit, ■... third amplifier circuit;

Claims (1)

[Claims] A light-receiving element detects light scattered by smoke from light emission pulses intermittently output from a light-emitting element, converts the light into an electrical signal, and outputs an electrical signal according to the smoke density. A photoelectric analog smoke detector configured as follows: a light-receiving signal amplification circuit that amplifies the electrical signal photoelectrically converted by the light-receiving element, an integrating circuit that integrates the output of the light-receiving signal amplifying circuit, and a second circuit that amplifies the output voltage of the integrating circuit. a second amplifier circuit that inverts and amplifies the output voltage of the first amplifier circuit based on a voltage value within a range of the output voltage, and an output voltage of the second amplifier circuit; A photoelectric analog smoke detector comprising: a third amplification circuit that inverts and amplifies a voltage value within the range of .