JPH03100897A - Extinction type smoke sensor - Google Patents

Abstract

PURPOSE:To accurately take synchronization between light emitting and receiving parts by setting the operation completing time of a clock means so as to be set after the recovery of a line voltage. CONSTITUTION:When a voltage cut off intermittently from the power source supply cutoff means 26 of the light receiving part 2 is supplied to the light emitting part 1, voltage drop detecting means 12, 28 detect the voltages on lines 3, respectively, and when the voltages drop less than a prescribed voltage, a detection signal is outputted to each of first timers 13, 29. The first timers 13, 29 start their operations with the detection signal, and output pulses for first prescribed time. Second timers 14, 30 provided at the output sides of the first timers 13, 29 start their operations synchronizing with the leading or the trailing edgde of the pulse, and when the pulse is outputted for the prescribed time, the light emitting part 1 makes a light emitting device LD emit light for that period, and a smoke detecting operation is performed while the second timer 30 is being operated at the light receiving part 2. In such a way, it is possible to prevent the malfunction of the light emitting and receiving parts occurring even when a source voltage is cut off intermittently.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dimming type smoke detector comprising, for example, a light emitter and a light receiver, and in particular, to a light emitting operation of the light emitter and a smoke detection operation of the light receiver. This is related to synchronization with

[Prior Art] Conventionally, this type of circuit is disclosed in Japanese Patent Publication No. 59-32838,
Disclosed in Japanese Patent Application Laid-Open No. 63-53448, etc., among which,
In Japanese Patent Publication No. 59-32838, the power supply voltage supplied from the light receiving section to the light emitting section is intermittently cut off, and while the voltage is cut off, the light emitting section is caused to emit light, and the light receiving section is intermittently cut off. Smoke detection is performed in synchronization with the light emission. Furthermore, in Japanese Patent Application Laid-open No. 83-53446, the power supply voltage is intermittently interrupted and supplied to the light emitting section. Then, the light emitting section is caused to emit light in synchronization with the rise of the voltage from the time when the voltage is cut off, and the light receiving section performs a smoke detection operation in synchronization with the intermittent light emission.

Problem to be solved by invention C] In the former prior art, the light emitting part emits light and the light receiving part performs smoke detection operation while the power supply voltage is cut off, but the light receiving part and the light emitting part are connected. Due to the influence of the capacitance between the lines, the time when light emission starts is delayed from the time when the power supply voltage starts to be cut off, and the time is not constant. Therefore, there is a drawback that the light receiving section starts the smoke detection operation before the light emitting section emits light. Furthermore, since the light emitting section emits light while the power supply voltage is cut off, there is a problem in that a large amount of charge must be stored on the light emitting section side.

In the latter prior art, the rise of the voltage between the lines is used as a synchronization signal, but because the synchronization signal is delayed with respect to the voltage rise time due to the capacitance between the lines, the light emission start time of the light emitting section is delayed by the smoke detection operation of the light receiving section. There is a problem in that there is a delay in the start of the process, resulting in malfunctions. Furthermore, when the rise of the voltage is used as a synchronization signal, the light emitting section malfunctions and emits light due to the induced noise, resulting in a problem in that the amount of light emitted during normal light emission is reduced and false alarms are generated.

This invention was made to solve this problem, and is a dimming type that prevents the light emitting part and the light receiving part from malfunctioning even if the power supply voltage supplied from the light receiving part to the light emitting part is interrupted intermittently. Aim to get a smoke detector.

[Means for Solving the Problems] A dimming type smoke detector according to the present invention is provided in a light receiving section,
a power supply cutoff means for intermittently cutting off the power supply voltage supplied to the light projecting section via a pair of lines; and a power supply cutoff means provided in each of the light receiving section and the light projecting section, and detecting the voltage between the pair of lines;
Voltage drop detection means outputs a detection signal when the voltage cut off among the voltages cut off intermittently becomes lower than a predetermined voltage; The first detection signal is input from the detection means.
a first timer that operates for a predetermined time; and a first timer that is provided on the output side of the first timer, starts operating in synchronization with the completion of the operation of the first timer, and operates for a second predetermined time. and a second clock means.

[Operation] In this invention, when the voltage that is intermittently cut off from the power supply cutoff means provided in the light receiving section is supplied to the light projecting section via a pair of lines, the light receiving section and the light projecting section Voltage drop detection means provided in each of the lines detects the voltage between the lines. The voltage detected by the voltage drop detection means is the voltage to be cut off, and when the voltage falls below a predetermined voltage, a detection signal is output to each first timer.

The first timer starts operating when the detection signal is input, and outputs a pulse for a first predetermined time, or
Outputs a trigger signal when activated for a predetermined period of time. The second timer provided on the output side of each first timer starts operating in synchronization with the falling or rising edge of the pulse output from the first timer or the trigger signal,
A pulse is output for a second predetermined period of time. At this time, the light projecting section causes the light emitting element to emit light during the second provisional time, and the light receiving section performs the smoke detection operation while the second timer in the light receiving section is operating.

〔Example〕

FIG. 1 is a block diagram of a separate dimming type smoke detector showing an embodiment of the present invention, FIG. Figure 3 is a time chart.

In Figure 1, (1) is the light emitter, (2) is the light receiver, (
3) is a pair of power and synchronization signal lines connected between the light emitter (1) and the light receiver (2), and (4) is the line between the light receiver (2) and a fire receiver or repeater (not shown). The power and signal line (5) connected between them is a luminous flux emitted from the light emitter (1), received by the light receiver (2), and attenuated by smoke, (11
) is a constant voltage circuit.

(12) is a voltage drop detection circuit that detects a voltage drop as a synchronization signal between the power supply and synchronization signal line (3), and (13) is activated by the output of the detection signal from the voltage drop detection circuit (12). , a first timer (14) that outputs a pulse for a predetermined T1 time is provided on the output side of the first timer (13), and is set at the falling edge of the pulse output from the first timer (13). Starts operation synchronously and for a prescribed 12 hours,
This is a second timer that outputs a pulse.

(15) While the second timer (14) is operating, the transistor (Tri) is driven and the light emitting element (LD) is activated.
(R1) is a resistor, and (CI) is a capacitor that discharges current when the transistor (Tri) is turned on.

(21) is a light receiving element made of, for example, a solar cell, a photodiode, etc., which receives the luminous flux (5) emitted from the light emitting element (LD) of the light projecting section (1) and converts it into an electrical signal. (
21a) is an amplifier, (22) is a sample and hold circuit that samples and holds the output signal amplified by the amplifier (21a), and (23) is, for example, an A/D converter, a microcomputer, etc., and performs a fire discrimination operation. This is a fire detection circuit.

(24) is a constant voltage circuit provided in the light receiving section (2);
5) is operated by the fire detection signal from the fire discrimination circuit (23), and is connected to the power supply/signal line (4) by, for example, SCR.
A fire signal sending circuit (2B) which sends out a fire signal by short-circuiting between the two with low impedance, supplies power supply voltage to the light emitter (1) by the output of the oscillator (27), for example, for 100 μs every 3 seconds. This is a power supply cutoff circuit that cuts off the power supply only during this period.

(28) is a voltage drop detection circuit that detects when the voltage between the power supply and synchronization signal line (3) has dropped below a predetermined voltage;
9) is provided in the light receiving section (2) and is connected to the voltage drop detection circuit (2).
8) The operation is started by the output of the detection signal, and the predetermined T1
A first timer (30) that outputs time and pulses is provided on the output side of the first timer (29) provided in the light receiving section (2), and the first timer (30) outputs time and pulses. This is a second timer that starts operating in synchronization with the falling edge of the pulse and outputs a pulse for a predetermined 12 hours.

Note that, assuming that the power supply voltage cutoff time by the power supply cutoff circuit (26) described above is 100 μs, the first timer (1
The predetermined T1 time set in 2) and (29) is longer than the time from when the voltage is interrupted until it is recovered, and is set to, for example, 1 msec.

Further, the predetermined 12 hours set in the second timers (14) and (30) are set to a light emission time necessary for smoke detection, for example, 1 msec.

Figure 2 shows the constant voltage circuit (11) of the above-mentioned light projector (1).
and shows a circuit configuration diagram of the voltage drop detection circuit (12).

A voltage drop detection circuit (28) provided in the light receiving section (2)
) has the same circuit configuration as its voltage drop detection circuit (12).

In the figure, normally the capacitor (C2) is charged with the output voltage of the constant voltage circuit (11), and the base potential of the transistor (Tr2) is high due to the voltage drop of the resistor (R2). , is in a non-conducting state, and the constant voltage diode (ZDI) and transistor (Try) are also in a non-conducting state. As a result, the output terminal (t6) is in an H level output state.

The input voltage from the input terminal (t4), that is, the voltage between the power supply and synchronization signal line (3) decreases, and the transistor (Tr2)
) becomes lower than the value of the following equation, the Zener voltage of the constant voltage diode (201) + the transistor (T
r2) base-emitter voltage) of that transistor (
A base current flows through Tr2), making it conductive. Therefore, the other transistor (Try) becomes conductive. As a result, the output terminal (t6) becomes an L level output state, and outputs a detection signal to the first timers (13) and (29), causing them to operate once.

Note that the capacitor (C2) functions as a power source for the voltage drop detection circuit (12) when the voltage drops, and the diode (DI) serves as a power source for the voltage drop detection circuit (12) when the voltage drops, and the diode (DI) serves as a power source for the voltage drop detection circuit (12) when the voltage drops. This is to prevent internal voltage drop due to the influence of the circuit. Further, the diode (D2) is used to prevent reverse bias of the transistor (Tr2) during normal operation.

Next, the operation will be explained based on FIGS. 1 and 3. The power supply cutoff circuit (26) of the light receiving unit (2) is connected to the oscillator (27
), the third
As shown in Figure (a), a power supply voltage whose voltage is cut off for 100 μs every 3 seconds is sent to the light projector (l,) via the power supply and synchronization signal line (3). The voltage between the power supply and synchronization signal line (3) decreases due to the capacitance between the lines (3) as shown in FIG.
) and the voltage drop detection circuits (12) and (2) of the light receiving section (2).
g) respectively transmit the detection signals to the first timers (11) and (2).
9). In response to the input of the detection signal, the first timers (18) and (29) output pulses for a predetermined time T1, for example, 1 msec, as shown in FIG. 3(e).

First timer (1B).

When (29) times up, the second timer (14)
.

(30) start operating synchronously, as shown in Fig. 3(d).
For a predetermined 12 hours required for smoke detection, e.g.
Outputs a pulse for m seconds. At this time, the light projecting section (1)
Now, when the light emission control circuit (15) generates a pulse signal based on the pulse output of the second timer (!4) and turns the transistor (Trl) on and off intermittently, the capacitor (CI) discharges the charging current through the resistor (R1) and the light emitting element (LD) according to its operation. Therefore, the light emitting element (LD) emits pulsed light as shown in FIG. 3(e).

Further, in the light receiving section (2), the sample and hold circuit (22) is turned on as shown in FIG. 3(f) by the output of the second timer (30), and samples and holds the maximum light receiving and amplifying output. When the sampling of the light reception output is completed, the sample hold circuit (22) outputs a sample hold completion signal to the fire discrimination circuit (23).

Note that in the above embodiment, the first timer (18).

(29) outputs a pulse during the first predetermined time T1, but a trigger signal may be output to the second timer (14), (80) when the first predetermined time T1 elapses. Further, the first timer (ta), (29) and the second timer (14), (80) are connected to the light emission control circuit (1).
5) Alternatively, the timekeeping function of a microcomputer provided in the fire discrimination circuit (23) or the like may be used.

[Effects of the Invention] As described above, according to the present invention, the operation end time of the first timing means is set to be after the inter-line pressure has been recovered, so that the light emitting operation of the light emitting section is controlled by the capacitor. Since not only the capacitance but also the power supply voltage supplied from the light receiving section can be used, a stable light emitting state and light emitting time can be obtained.
The timer means is activated, and the time-up output is used to activate the second timer means to perform light emitting and smoke detection operations, thereby achieving the effect that synchronization between the two can be performed accurately. .

[Brief explanation of drawings]

FIG. 1 is a block diagram of a separate dimming type smoke detector showing an embodiment of the present invention, FIG. 2 is a circuit configuration diagram of a constant voltage circuit and a voltage drop detection circuit provided in a light projecting section, and FIG. The figure is a time chart. In the figure, (l) is the light emitting part, (2) is the light receiving part, (11
) is a constant voltage circuit, (12) is a voltage drop detection circuit, (13
) is the first timer, (14) is the second timer, (15)
is a light emission control circuit, (22) is a sample hold circuit, (
23) is a fire discrimination circuit, (20 is a constant voltage circuit, (25)
is the fire signal sending circuit, (2B) is the power supply cutoff circuit, (
28) is a voltage drop detection circuit, (29) is a first timer,
(30) is a second timer.

Claims (1)

[Scope of Claims] Power supply cutoff means provided in the light receiving section and for intermittently cutting off the power supply voltage supplied to the light projecting section via a pair of lines; , a voltage drop detection means for detecting the voltage between the pair of lines and outputting a detection signal when the voltage to be cut off among the voltages to be cut off intermittently becomes a predetermined voltage or less; a first timer provided on the output side of the detection means and activated for a first predetermined period of time in response to input of a detection signal from the voltage drop detection means; It starts its operation in synchronization with the end of the operation of the first timing means, and the second
and a second timer that operates for a predetermined period of time, the light emitting element emits light while the second timer provided in the light emitting part is in operation, and the second timer provided in the light receiver is activated. A dimming type smoke detector characterized by a smoke detection operation.