JPH0833963B2 - Photoelectric analog smoke detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoelectric analog smoke detector used in an automatic fire alarm system or the like.

[Background Art] Photoelectric smoke detectors that detect smoke by placing light-emitting elements such as LEDs and light-receiving elements such as photodiodes in the chamber and receiving scattered light from the smoke flowing into the chamber by the light-receiving elements It is widely used in notification systems (hereinafter, abbreviated as "self-fire alarm system") and the like.

Among such smoke detectors, the conventional photoelectric smoke detector is
This is a so-called ON / OFF type that sends a smoke detection signal when the output value of the light receiving element exceeds a certain threshold value. Recently, in order to detect fires early and improve their reliability, an intelligence self-fire alarm system is being developed, which allows the receiver to judge the fire. Must be sent every second.

And, since such information simplifies the design of the system, there is a certain relationship (eg, Y = A · x + B,
Here, it is desired to have A: constant, B: sensor output when smoke density is 0, x: smoke density).

Also, considering the state in which the smoke sensor is placed, there is a possibility that a false alarm or a false alarm may occur due to deterioration of the light emitting element, contamination of the light emitting element or the light receiving element, or intrusion of dust into the chamber. It is desired that detection be easily performed.

[Purpose of the Invention] The present invention has been made in view of such a current situation, and an object of the present invention is to obtain an output having a constant relationship with smoke concentration required in an intelligence self-ignition alarm system. Further, it is another object of the present invention to provide a photoelectric analog smoke detector which can easily determine deterioration of a light emitting element, contamination of a light emitting element or a light receiving element, or intrusion of dust or the like into a chamber by its output.

DISCLOSURE OF THE INVENTION In order to achieve the above object, the photoelectric analog smoke detector of the present invention detects scattered light due to smoke of light emission pulses intermittently output from the light emitting element by the light receiving element, and the light receiving element detects the scattered light. In a photoelectric analog smoke sensor configured to convert into an electric signal and output an electric signal according to smoke density, a light receiving signal amplifier circuit for amplifying the electric signal photoelectrically converted by a light receiving element, a light receiving signal amplifier circuit An integrating circuit for integrating the output of the first amplifying circuit, a first amplifying circuit for amplifying the output voltage of the integrating circuit, a second amplifying circuit for inverting and amplifying the output voltage of the first amplifying circuit based on a first reference level, And a third amplifier circuit that inverts the output voltage of the second amplifier circuit with the second reference level as a reference and amplifies the output voltage, and the output of the integration circuit is y = a · x + b (a Is the increase factor of smoke density, b Is the offset value when the smoke density is zero, and x is the smoke density), and the first reference level is set within the range where the output of the first amplifier circuit is not saturated and a linear output is obtained. The above-mentioned second reference level is a linear output required by design in the range from zero to maximum smoke concentration: Y = Ax + B (A is a constant of smoke concentration increase coefficient, B
Is an output value when smoke density is zero, and x is a smoke density).

Embodiment An embodiment of the present invention is shown in FIG. In the figure, 2 is placed in the chamber 3 of the photoelectric analog smoke detector 1.
Reference numeral 4 denotes a light emitting element formed of an LED or the like, and reference numeral 4 denotes a light receiving element also formed of a photodiode or the like arranged in the chamber 3. The light emitting element 2 is intermittently driven by the light emitting element drive circuit 5 to output a light emitting pulse, and the light receiving element 4 receives a scattered light due to smoke of the light emitting pulse to generate a light receiving signal. This signal is amplified by the received light signal amplification circuit 6 and sent to the integration 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 is received by the light receiving element 4, so that even if the smoke density is zero, the received light signal is amplified. A certain voltage appears at the output of the circuit 6. Therefore, the relationship between the smoke concentration x and the output voltage y of the integrating circuit 7 is generally y = a × x + b (Equation 1) (where a is a constant of smoke concentration increase coefficient, and b is zero smoke concentration). This is the offset value of the integrating circuit 7 at the time.), And this (Formula 1) is unique to the integrating circuit 7 to be adopted.

However, when designing an actual intelligence self-warning system, the relationship between the smoke concentration x and the output voltage Y of the smoke sensor 1 is required to have a relationship different from the above (Equation 1). Is generally expressed by the following (Equation 2).

Y = A · x + B (Equation 2) (where A is a constant for the smoke concentration increase coefficient, B is the output voltage of the smoke sensor 1 when the smoke concentration is zero, and A and B depend on the system to be designed. Therefore, the relationship of (Equation 2) cannot be obtained simply by amplifying (Equation 1). Therefore, according to the present invention, the output of the integrating circuit is amplified by the first amplifying circuit I and then inverted and amplified by the second and third amplifying circuits II and III to obtain a desired output. There is.

The amplifier circuits I to III are composed of operational amplifiers 11 to 13, and the resistors R1 to R11 are connected as shown in the figure. Therefore, the amplification degrees A1 to A3 of the amplifier circuits I to III are A1 = 1.
+ R3 / R2, A2 = R7 / R6, A3 = R11 / R10.

The output y of the integrating circuit 7 is input to the first amplifier circuit I, and is input to the non-inverting input terminal of the operational amplifier 11 via the resistor R1. The output V1 of the amplifier circuit I is input to the second amplifier circuit II, and is connected to the operational amplifier via the resistor R6.
Input to 12 inverting input terminals. Output of amplifier circuit II
V2 is further input to the inverting input terminal of the operational amplifier 13 forming the third amplifier circuit via the resistor R10. The input voltages supplied to the non-inverting input terminals of the operational amplifiers 12 and 13 as the first and second reference levels are indicated by VS1 and VS2. The output V3 of the amplifier circuit III thus obtained is sent to the receiver (not shown) of the intelligence fire alarm system as the output of the smoke sensor 1 (Y in Expression 2).

According to such a configuration, the following relational expression holds.

V1 = A1 (ax * b) (Equation 3) A2 (V1-VS1) = VS1-V2 (Equation 4) A3 (V1-VS2) = VS2-V3 (Equation 5) When these equations are summarized, V3 = A1・ A2 ・ A3 ・ a ・ x + A1 ・ A2 ・ A3 ・ b −A3 (1 + A2) VS1 + (1 + A3) VS2 (Equation 6) is obtained.

Here, A1 · A2 · A3 · a = A (Equation 7) A1 · A2 · A3 · b-A3 (1 + A2) VS1 + (1 + A3) VS2 = B (Equation 8) = A · x + B, and the analog signal output shown by (Equation 2) required by the fire alarm system side can be obtained. Therefore, when designing the actual system, each resistance value can be changed according to A and B required by the system. May be selected appropriately. In the normal case, the output V3 when the smoke density is 0 (x = 0) is B expressed by (Equation 8).

A design example of the system according to the present invention will be described more specifically with reference to the examples shown in FIGS. 2 and 3. Now, in this example, as shown in FIG. 2, when the smoke density is 0% / m, 100 m
When V and smoke density 22.5% / m, a voltage of 700 mV is generated as the output y of the integrating circuit 7 (that is, y = 2.67x + 0.
1). However, on the receiver side of the fire alarm system, as shown by the solid line in Fig. 3, when smoke concentration is 0% / m, 1V,
It is assumed that a voltage of 5V is required as the output Y of the smoke sensor 1 when the smoke density is 22.5% / m (that is, Y = 17.8x + 1).

The resistors R2 and R3 of the first amplifier circuit I are set to, for example, 10 kΩ and 90 k
When Ω is set (amplification degree A1 = 10), the output V1 of the amplifier circuit I becomes 1V at 0% / m and 7V at 22.5% / m as shown by the solid line in FIG. In the second amplifier circuit II, both resistors R6 and R7 are set to 10
If 0 kΩ (amplification A2 = 1) and the first reference level VS1 of the non-inverting input terminal is 4 V, the output V1 is input to the inverting input terminal, so the output V2 of the amplifier circuit II is the first The output V1 is inverted with respect to the reference level VS1 (= 4V) of (1). Next, the third amplifier circuit
III resistance R10 is 600kΩ, R11 is 400kΩ (amplification A3 = 2
/ 3), and set the voltage VS2 to 3.4V. Since the output V2 of the amplifier circuit II is input to the inverting input terminal, the output V2 of the amplifier circuit III is
3 (that is, the output Y of the smoke sensor 1) is the output V2 inverted with respect to the second reference level (= 3.4V) (solid line in FIG. 3). Therefore, the output Y of the smoke sensor 1 is as required by the system side.

Next, consider the case where the output Y (V3) of the smoke sensor 1 deteriorates the light emitting element 2, the light emitting element 2 or the light receiving element 4 is contaminated, or dust enters the chamber 3 as described above. .

In this case, due to deterioration of the light emitting element 2 and contamination of 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 = 0) becomes smaller than b and becomes b1 (b1 <b). . By the way, since the output V3 (= B1) of the smoke detector 1 at this time is the one where x = 0 and b = b1 in (Equation 6), V3 (= B1) = A1 ・ A2 ・ A3・ It becomes b1-A3 (1 + A2) VS1 + (1 + A3) VS2. Therefore, the output V3 (= B
1) is A from the output V3 (= B) when the smoke density is 0 in the normal case
It becomes smaller by 1 · A2 · A3 (b−b1). If the value of B when the smoke detector is normal is stored in the receiver side, this change can be discriminated, and the abnormality such as deterioration of the light emitting element 2 and dirt of the light emitting element 2 or the light receiving element 4 is detected. Can be detected.

Next, dust enters the chamber 3 and smoke density becomes 0 (x =
0), the output y of the integrating circuit 7 becomes larger than b, and y =
Consider the case where b2 (b2> b). The output V3 (= B2) of the smoke detector 1 at this time is x = 0, b in (Equation 6).
= B2, so V3 (= B2) = A1 ・ A2 ・ A3 ・ b2-A3 (1 + A2) VS1 + (1 + A3) VS2. Therefore, the output V3 (= B
2) is A from the output V3 (= B) when the smoke density is 0 in the normal case
It increases by 1 ・ A2 ・ A3 (b2-b). By the way, the value of the output V3 increased by dust is constant with time, but the output V3 by smoke greatly changes in a short time, so that it is possible for the receiver side to determine that the output is changed by dust.

As the integrating circuit 7, a sample hold circuit may be used instead of the normal integrating circuit. Further, although an example in which an LED is used as the light emitting element is shown, it goes without saying that a laser beam may be used.

[Effects of the Invention] As is apparent from the above description, according to the present invention, even if the output characteristic of the integrating circuit is different from that of the system such as the intelligence self-ignition report system, the system side requests it. An analog output signal having a constant relationship with the smoke density can be obtained, and the output signal can easily determine deterioration of the light emitting element, contamination of the light emitting element or the light receiving element, or intrusion of dust or the like into the chamber.

[Brief description 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 concentration, and FIG. 3 is the output of a smoke detector according to the present invention and smoke concentration. It is a graph which shows an example of the relationship of. 1 ... Photoelectric analog smoke detector, 2 ... Light emitting element, 3 ...
... light receiving element, I ... first amplifying circuit, II ... second amplifying circuit, III ... third amplifying circuit, VS1 ... first reference level, VS2 ... second reference level.

Claims (1)

[Claims] 1. A light-receiving element detects scattered light by smoke of light-emission pulses intermittently output from the light-emitting element, and the light-receiving element converts the scattered light into an electric signal to output an electric signal according to smoke concentration. In the configured photoelectric analog smoke detector, a light receiving signal amplifying circuit for amplifying an electric signal photoelectrically converted by the light receiving element, an integrating circuit for integrating the output of the light receiving signal amplifying circuit, and a first amplifying an output voltage of the integrating circuit. Amplifier circuit, a second amplifier circuit that inverts and amplifies the output voltage of the first amplifier circuit based on the first reference level, and an output voltage of the second amplifier circuit based on the second reference level. A third amplifier circuit for inverting and amplifying is provided, and the output of the integrator circuit is y = a · x + b (a is an increase coefficient of smoke concentration and b is an offset value when the smoke concentration is zero). , X is the smoke density) The first reference level is set to a range where a linear output can be obtained without saturating the output of the first amplifier circuit, and the second reference level is set from a smoke density of zero to a maximum density. Linear output required by design in all ranges: Y =
A photoelectric analog smoke detector characterized by being set to a range in which Ax + B (A is an increase coefficient of smoke density, B is an output value when smoke density is zero, and x is smoke density) can be obtained.