JPS58162843A - Photoelectric type smoke detector - Google Patents

Abstract

PURPOSE:To secure high reliability and also, to reduce a consumption of electric current and production cost, by reading an output of a comparison circuit obtained by synchronizing with a luminous pulse in an accumulation circuit at the timing of tailing edge of said pulse. CONSTITUTION:Electric power is supplied to a light emission diode 5, a reference voltage setting circuit 12 and a comparator 15 by a pulse generating circuit 11 by synchronizing in a form of a pulse having about 2-3sec cycle. On one hand, scattered light by smoke which is flowed in a smoke detection part is received by a photodetecting diode 13 and an output of the comparator 15 is read in an FF1 of an accumulation circuit 16 at the time when density of the smoke is exceeded the predetermined density and the light emission of the diode 5 is finished, and a terminal Q becomes an H level. Hereafter, the output of the terminal Q is charged to a capacitor C5 and is read in an FF2 of the succeeding stage delaying about 20-30sec and its terminal Q becomes the H level. Hereby, a thyristor 17 of a switching circuit 2 is turned on through a Zener diode ZD3 and the power source which serves also as signal line between l1 and l2 is short-circuited and a fire alarm is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric smoke detector that detects scattered light caused by smoke flowing into a smoke detection section and sends an alarm signal to a receiver, and particularly relates to a photoelectric smoke detector that ensures high reliability. The present invention relates to a photoelectric smoke detector designed to significantly reduce current consumption and manufacturing costs.

Conventionally, the first type of photoelectric smoke detector made of cypress wood has not been put into practical use. In the figure, in the lij diode bridge, following this diode bridge 1, there is a switching circuit 2 having a thyristor that conducts between the power supply signal line t1 + 22 and sends out an alarm signal when a fire is detected, and a current limiter. A constant voltage circuit 3 with a function, an oscillation circuit 4 including a pulse control circuit, a light emitting diode 5 that is driven to emit light intermittently in response to a pulse signal from the oscillation circuit 4,
A comparison circuit 8 having a light receiving diode 7 that receives scattered light due to smoke flowing into the detection section 11, and a comparator that outputs when the output voltage obtained from the wrinkled light receiving diode 7 is equal to or higher than a reference voltage.
, and an accumulation circuit 9 which outputs a fire detection signal and activates the switching circuit 2 when the output of the comparison circuit 8 is obtained twice or more in succession.

By the way, in the above-mentioned conventional photoelectric smoke detector, when the drive current of the light emitting diode is lowered to reduce current consumption, the output of the light receiving diode decreases due to this, and an operational amplifier with a high gain of 500 to 1000 times is used. Generally, compensation is provided by providing an amplifier (not shown) in the comparator circuit 8 before the comparator. However, when a high gain amplifier is used to amplify a received light voltage of several mV, the comparator circuit 8 will output an inverted output even if an extremely small amount of noise, for example 1 mVa noise, is added due to electromagnetic induction or electrostatic induction. It has the disadvantage of causing malfunctions due to

When an operational amplifier with two power supplies is used as an amplifier, the power supply voltage is divided by a Zener diode or a dividing resistor to obtain the midpoint potential t, but it is necessary to reduce the current consumption by using a Zener diode or a dividing resistor. Moreover, these elements tend to have high impedance, and the midpoint potential fluctuates due to noise, resulting in the same malfunction as described above.

Therefore, in the conventional sensor, the entire circuit section is housed in a shield case 10, as shown by the broken line in FIG. 1, to prevent malfunctions caused by external noise. However, even if the circuit part is completely shielded by the shield case IO, the circuit part is still connected to the power supply and signal 1fil.
t1. t2, and is affected by noise through these, which may cause malfunction. Furthermore, it is difficult to provide a shield case that shields the circuit to near full pressure because it is quite expensive.

In order to reduce current consumption, this elm sensor has a structure in which, in addition to the above-mentioned nine measures, the light emitting diode 5 is intermittently pulse-driven. Furthermore, power is intermittently supplied to the comparison circuit 8 from the oscillation circuit 4 in synchronization with the driving of the light emitting diode 5, so that the comparison operation is performed only while pulsed light is being output. In this case, if the reading timing of the output of the comparison circuit 8 in the storage circuit 9 is synchronized with the light emission pulse, the 21st
As shown in FIG. 11K, due to the delayed response of the high gain amplifier and comparator that make up the comparator circuit 8 and the accumulation of unstable states at the time of rise, the comparator output reaches the threshold level of the storage circuit 9. Since it takes time, a problem arises in that an appropriate comparison output cannot be manually input to the storage circuit 9.

On the other hand, the reading timing of the storage circuit 9 is estimated in advance by estimating the above-mentioned required time, and is delayed by a certain period of time after the rise of the light emitting pulse, for example, by τ shown as the &include timing in FIG. 2 using a delay circuit (not shown). It is proposed to set. However, with this method, the delay time setting is
Due to turning off the hood of the delay circuit and comparison circuit 8, aging, etc., the relative square changes, causing a shift in the read timing, which may prevent proper insertion in the storage circuit.

The present invention was made in view of such circumstances, and
The first purpose is to set the output of the comparator circuit, which is synchronized with the light emitting pulse, to be read by the storage circuit at the timing of the falling edge of the light emitting pulse (the trailing edge of the pulse). It is an object of the present invention to provide a photoelectric smoke detector in which the data reading operation when supplying data is made appropriate, and furthermore, by omitting a delay circuit or the like, the circuit is simplified and the consumption is reduced.

The second object of the present invention is to reduce the driving current of the light emitting diode by configuring it so that a large light receiving output can be obtained by using a light receiving diode with a small junction capacitance and a resistor having a corresponding high resistance value. However, it is possible to obtain a photodetection output of sufficient voltage for direct comparison with a comparator without installing a high-gain amplifier, reduce problems such as noise associated with high-gain amplification, and reduce current consumption. It is an object of the present invention to provide a photoelectric smoke detector which can be manufactured at a lower cost by simplifying the circuit configuration by omitting a high gain amplifier and by eliminating the need for a shield case which is necessary for noise countermeasures.

That is, the present invention includes a light emitting diode that is driven to emit light intermittently and emits pulsed light to a smoke detection section into which smoke flows, and a light emitting diode that receives scattered light from the smoke that has flowed into the smoke detection section and converts it into an electrical signal. A light receiving diode and the output signal of the above light receiving diode are input to one input terminal, and a predetermined reference voltage is input to the other input terminal, and when the output voltage of the above light receiving diode becomes equal to or higher than the reference voltage, the output signal is output. A comparator that stores the output of the ratio IIR device and outputs the output when the output of the comparator is obtained at least twice in a row in synchronization with the light emission pulse, and the output of the skeleton storage circuit. 4, and a switching circuit that sends an alarm signal by switching between the edges of a pair of power supply signals drawn out from the receiver, and the queen storage circuit is connected to the output of the comparator at the timing jig of the trailing edge of the emission pulse. It is constituted by a flip-flop circuit that inputs the data and latches it.

The present invention will now be described based on embodiments shown in the drawings.

FIG. 3 is a block diagram showing an embodiment of the inventive photoelectric type difference detector. The smoke detector of the present invention shown in the figure includes a diode bridge 1 connected to t# and signal ridge A1+t2,
When a fire is detected, a switching circuit 2 short-circuits the power and signal lines t1 + t2 and sends out an alarm signal, a constant voltage circuit 3 with a current limiting function, and is charged from the constant voltage circuit 3 via a diode DI. and an electrolytic capacitor C1 for supplying power to each circuit subsequent to 5, and a light emitting diode 5, a reference voltage setting circuit 12, and a comparator 15.
and a pulse generation circuit 11 that drives these intermittently,
Light receiving diode 13 with low junction capacitance and resistor R with high resistance value
O, and a storage tank circuit 16.

In addition, the power supply/signal lines tl and t2K are provided with an alarm indicator light and its lighting circuit (none of which are shown) in the human power 9111 of the diode bridge 1 to display the alarm of the sensor. be.

Constant voltage circuit 3#-1,) Consists of a constant voltage circuit section 3a having a transistor Tri, and a current limiting circuit section 3b having a transistor Tr2. The former is diode bridge 1
The output voltage, for example 22V, is stabilized to about 13V by constant voltage control of the transistor Tri based on the reference voltage by the Zener diode ZD2. The latter is a transistor Tr
2, one load VI51t-1 when the power is turned on, for example 1
It is limited to not exceed 60μA.

Pulse generation circuit 11Fi1. A transistor Tr3 acting as a switching element, resistors R5 and R6 forming a bias circuit thereof, and the transistor Tr3tl
- It is constituted by a transistor Tr4 that turns on and off, resistors R3 and R4 that turn on and off the transistor Tr4 at a predetermined period, and a capacitor C2. Resistor R3Fi
, for example, a high resistance I1 of 4.7 MΩ is selected to gradually discharge the capacitor C2. Resistance R
It is generally determined that a low resistance value of 4Fi, for example 15Ω, is selected to rapidly charge the capacitor C2 with the polarity shown.

This pulse generating circuit 11 includes transistors Tr3 and Tr3.
Pulse outputs having mutually inverted phases are taken out from the collectors 4 and 4, respectively. The collector of the transistor Tr3 is connected to the light emitting diode 5, the reference voltage setting circuit 12, and the comparison 1115 through the resistor R7, respectively! II
It is continued. On the other hand, the collector of the transistor Tr4 is a storage circuit to be described later! 7th Lip Float FFI
, FF2's CL (ri/ttsuk) terminal K11l is connected b
Ru.

The pulse generation circuit 1 uses a light emitting diode 5tlj, for example, a one-shot infrared light emitting diode with high luminous efficiency.
Charge is intermittently supplied from the capacitor CI in response to the on/off of the first transistor Tr3, and pulsed light is emitted.

Light-receiving diode 13#:t is connected in series with a high-resistance resistor RO, connected across capacitors C1 and C4, and reverse biased, and is irradiated with pulsed light from the light-emitting diode 5 (1%). Scattered light generated in response to the presence or absence of elongation in G (not shown) is detected. This light-receiving diode 13 uses a low junction capacitance having a junction capacitance of 1009 F or less. This is because the time constant of the rise of the light receiving voltage is determined by the junction capacitance of the light receiving diode and the resistance value of the resistor connected in series with the junction capacitance of the light receiving diode, so the pulse width of the pulsed light i 200
Even if it is as short as microseconds or less, if the photodiode has a junction capacitance of 100 pF or less, it can follow the pulse even if the resistance value of the series resistor is on the megmeme order, and as a result, the photodetection voltage can be pulled to tens of millivolts or more. , because it can make a beard. Since such a large light receiving voltage can be obtained, a high gain amplifier can be completely unnecessary.

As this light receiving diode 13, a PIN photodiode is suitable. The junction capacitance of this PIN photodiode decreases due to the reverse bias voltage, resulting in an appropriate noise of 20 to 6
The junction capacitance is less than 0 pF, and the light t151 when receiving light
As F, an orange degree of several tens of nanoamperes can be obtained.

A differentiating circuit 14 consisting of a capacitor C3 and a resistor RIO is connected to the connection point between the light receiving diode 13 and the resistor RO, and the light receiving voltage generated at the resistor RO is passed through the differentiating circuit 14 to the comparator 15 which will be described later. Inverting input terminal (+) K is input. This differentiating circuit 14 cuts the output due to the dark current Jd of the light receiving diode 13. For example, dark current l
When d is 1 nanoampere and resistor RO is 1 megohm, a voltage of 1 millivolt is generated in resistor RO, but this voltage is cut by the differentiating circuit 14 and the comparator 1s<F1
Not entered.

12 base SW pressure setting circuits, desired voltage of diode D2 is approximately 0
．． The configuration is such that a reference voltage is obtained by dividing 6 volts through a variable resistor VRK, and when the transistor 'l'r3 of the pulse generation circuit MII is turned on, it receives the power supply and generates a reference voltage t-. Input the inverting input terminal (->K) of the comparison 1915. Here, the diode D2 is used to set the base 5t8Et- so that the change in the output of the light receiving diode 13 with respect to the change in the light emitting characteristic due to the temperature of the light emitting diode 5 is This is to compensate by changing the reference voltage using the diode D2.The resistor R9F!,
This is to improve the resolution of the variable resistor Vl, and is not necessarily necessary.

The comparison 1115 constitutes a north wall circuit together with the reference voltage setting circuit 121 and the differentiating circuit 14, and compares the light receiving voltage inputted through the differentiating circuit 14 and the base s11 voltage inputted from the reference voltage setting circuit 12. , when the former is greater than or equal to the latter, H
(high) level output. This comparison [15] requires that the high-resistance RO has a sufficiently high input impedance, that the manual offset voltage and input offset current are sufficiently small relative to the input signal, and that it operates on a single power supply. On the other hand, the amplification gain may be 1000 times or more, which is the amplification degree of the simplest operational amplifier, and specifically, an operational amplifier with high input impedance using a MOS-F'ET in the input stage is used.

The storage tank circuit 16 is a D flip-flop FFI.

The H signal of the comparator 15 is configured by connecting two stages of FFZs, and the H signal of the comparator 15 is input to the D terminal of the first stage D flip-flop FFI.
The level output is stored for a predetermined time, and then the switching circuit 20 thyristor 17 is triggered via the malfunction prevention Zener diode ZD3 by the H level output from the Q terminal 31 of the D flip-flop FF2 in the next stage. D flip-flop FF, 1. The CL terminal of FF2 receives the falling light pulse (
A clock signal that rises in synchronization with the pulse II) is supplied, and in synchronization with the input of this clock signal, both D flip-flops FFI and FF2H1 each read the signal input to the D terminal and latch it. The Q terminal of the first stage D flip-flop FFI is connected to the resistor R11 and the resistor R12 &
It is connected to the D terminal of the next stage D flip-flop through an accumulation time extension circuit consisting of a diode D4 and a capacitor C5, and the H level output t-20 to 30 of the Q terminal is connected to the D terminal of the D flip-flop in the next stage.
It is configured so that the input data is enlarged by about a second. father,
The Q terminal of the first stage D flip-flop 1FFI is connected to the next stage D
It is connected to the R (reset) terminal of the flip-flop F2.

In this embodiment, an accumulation time extension circuit is provided, but this circuit is omitted, and the Q terminal of the first stage D flip-flop FFI is directly connected to the D terminal of the next stage D flip-flop FF2. Good too. In this case, comparator 1
When an H level output is obtained twice in succession from 5, the Q terminal output of the D flip-flop in the next stage becomes H level, and the thyristor 17'f is turned on.

The R terminal of the first-stage D flip-flop FFI and the Q terminal of the next-stage D flip-flop FF2 are connected to a resistor R13,
It is connected via a delay circuit consisting of R14 and a capacitor C6, and when the Q terminal of the next stage D flip-flop FF2 becomes H level, the thyristor 17
The configuration is such that the first-stage D flip-flop FFI is reset after a sufficient time has elapsed for the flip-flop to turn on.

Next, the operation of the photoelectric smoke detector of the present invention will be explained with reference to FIG. 3 and FIGS. 4 and 5 showing waveforms at various parts.

Now, when the power is turned on at the receiver side (not shown), the diode bridge 1 is connected via the power supply/signal II Lll '2.
A power supply voltage is applied to the capacitor C1, which charges the capacitor C1 via the constant voltage circuit 3.

Next, in the pulse generating circuit 11KTh, when both transistors Tr3 and Tr4 are off, the charge in the capacitor C2 is gradually discharged with a time constant determined mainly by the resistor R3. Then, when the pace potential of the transistor Tr4 rises, the transistor Tr4 is turned on. In the on state at this time, the resistor R3 has a high resistance, so it is in a semi-conducting state.

When the transistor Tr4 is turned on, the transistor Tr3 is turned on, and the capacitor C2 is turned on by the transistor 'rr31Tr.
4 and resistor R4, it is rapidly charged with the polarity shown in FIG. When this capacitor C2 reaches a predetermined terminal voltage, transistors Tr4 and Tr3 are turned off, returning to the above-mentioned initial state. By alternately repeating the above-described slow discharge through the resistor R3tl and rapid charge through the resistor E4, a pulse having a constant period, for example, in this embodiment, a period of about 2 to 3 seconds can be obtained.

One of the outputs of this pulse generation circuit 11 is obtained from the collector of the transistor Tr3, and its waveform is *41F+
is shown as a luminescence pulse at the top of the image. This output occurs during rapid charging, and in this embodiment has an extremely narrow vertical pulse width of about 100 microseconds. Father, this output is connected to the subsequent circuit through the transistor Tra and the capacitor CI.
Since it is obtained by directly connecting the transistor Tr4, it is possible to output a large amount of power, and synchronously supplies all the power in the form of pulses to the light emitting diode 5, the reference voltage setting circuit 12, and the comparator 15-.6 On the other hand, the collector of the transistor Tr4 The output from the above has a phase inversion of the above output, and is used as a clock signal for the D flip-flop 1FFI and FF2. This output, as shown as a clock signal in FIG. 4, rises just after the falling edge of the light emission pulse (pulse trailing edge).

The storage circuit 16 reads data input to the D terminals of the D flip-flops FFI and FF2 when the clock signal is input to the CL terminal. That is, the light emitting diode 5
At the end of the light emission, the output of the ratio voltage converter 15, which was turned off at the same time, is read. This is shown in enlarged No. 151)
As shown in the figure, the output of the ratio IIItI115 does not become KO at the time of off, but gradually decreases due to a certain time constant, and if it decreases after h1 is turned off, the output of the D-flip flora 1FFI
This is a precautionary measure, taking advantage of the fact that a data voltage higher than the threshold level of the D terminal can be obtained.

Now, if the g11 concentration starts to rise near time t3, the received light output, that is, the input of the comparator 15
It increases as shown in the figure. However, at this time, F'
Since the ifa concentration is not yet high enough, comparator 1
In No. 5, only a small portion exceeds the base pressure of 3 mm. Therefore, the pulse width of the output pulse from the comparator 15 is also narrow.
The output is not maintained above a predetermined level until the clock rises, and the D flip-flop FFI tlctd is not read. However, at time 1aVC, since the smoke concentration is higher than the preset concentration, the output of the comparator 15 is maintained at a predetermined level or higher until the clock signal is input manually, and the output of the D flip-flop FFI [9 included, Q end is H
become the level.

Thereafter, the output of this Q terminal is photoelectrically applied to the capacitor C5 via the resistor R11, and is delayed for a predetermined time, for example, about 20 to 30 seconds, and then the output of the D7 flip-flop 1FF2 of the next stage is
terminal, and the Q terminal of It must be maintained at a predetermined level or higher at the time of clock input.When the output of comparison 1[S falls below a predetermined level before the delay time elapses, the Q terminal of the first-stage 7-lip-flop FFI goes to L level, and the capacitor C5 The charging charge is transferred to the core Q via the resistor R12 and the diode D4.
This is because the terminal is rapidly discharged. By kneading, it is possible to prevent false alarms due to a temporary increase in smoke concentration caused by the smoke from the smoke screen.

When the Q terminal of the next-stage D flip-flop FF2 becomes H level, the thyristor 417 of the switching circuit 2 is turned on via the Zener diode ZDa, and the power supply/signal sl! t1. t2 is short-circuited and a fire is reported. After a certain period of delay in a delay circuit consisting of resistors R13, R14 and capacitor C6, the first-stage D flip-flop FFI is reset, and accordingly, the next-stage D flip-flop FFI is reset. The D flip-flop FF2 is reset and the 16 storage circuits are set to the initial state.

In the actual FM@ mentioned above, a pulse generation circuit that outputs narrow rectangular pulses was used as a means for intermittently driving the light emitting diode, but the configuration of this pulse generation circuit is not limited to that of this embodiment. Of course. For example, a structure may be adopted in which the light emitting diode or the like is not directly driven by the output of the pulse generation circuit, but is driven via an appropriate drive circuit.

As explained above, the present invention is configured to supply a clock signal to the storage circuit so as to read data from the output of the comparator circuit at the trailing edge of the light emission pulse. The data reading operation in the case is
This can be done properly without timing deviations due to temperature changes or aging, improving reliability.
Moreover, it is possible to omit a delay circuit, etc., which was conventionally necessary for setting the read timing, which has the effect of simplifying the circuit configuration and reducing current consumption.

Furthermore, the present invention reduces the driving chamber I51 of the light emitting diode by connecting a resistor with a high resistance value in series with the light receiving diode having a low junction capacitance, so that a large light receiving output can be obtained with a small time constant. Also, it is possible to obtain a light receiving output of sufficient voltage for a W-cross comparison in a comparator without providing a high-gain amplifier, and to reduce current consumption by reducing problems such as noise associated with high-gain amplification. Furthermore, by omitting the high gain amplifier, the circuit configuration can be simplified, and the manufacturing cost can be reduced by eliminating the need for a shield case, which was necessary for noise countermeasures.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional photoelectric smoke detector, Fig. 2 is a waveform diagram showing the operation of the conventional photoelectric smoke detector, and Fig. 3-1 is an example of the photoelectric smoke detector of the present invention. FIG. 4 is a waveform diagram showing the operation of the embodiment, and FIG. 5 is a waveform diagram showing an enlarged part of the circuit diagram. ]...Diode bridge 2...Switching circuit 3...Constant voltage circuit 4...Oscillation circuit 5
-4 photodiode 6...Smoke detection section 7.13...
Light receiving diode 8...Comparison circuit 9, 16...Storage tank circuit 10...Shield case 11...Pulse generation circuit 12...Reference voltage setting circuit 14...
・Differential circuit 15... Comparator ]7... Thyristor FF], FF2... D flip-flop Tri~Tr
4...Transistor VR...Variable resistor RO...
(High resistance value) Resistors R1-R14...Resistors C1-C
6...Capacitor D1-D4...Diode Applicant Hochiki Co., Ltd. Figure 4 Figure 5

Claims (1)

[Scope of Claims] A light emitting diode that is driven to emit light intermittently and emits pulsed light to a smoke detector into which smoke flows, and a light emitting diode that receives scattered light from the smoke that has flowed into the fan detector and converts it into an electrical signal Kf. A light receiving diode and the output signal of the light receiving diode are input to one input terminal, and a predetermined reference voltage is input to the other input terminal, and when the output voltage of the light receiving diode becomes equal to or higher than the reference voltage, the output signal is output. A comparator, an accumulation circuit that accumulates the output of the comparator and outputs it when the output of the skeleton comparator is obtained at least twice in a row in synchronization with the light emission pulse, and an output of the skeleton accumulator circuit. and a switching circuit that sends out an alarm signal by switching between a pair of power supply/signal lines drawn out from the receiver, and the storage tank circuit is connected to the ratio @H at the timing of the trailing edge of the light emission pulse. A photoelectric smoke detector comprising a flip-flop circuit that reads and latches the output.