JPH0248954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention generates an alarm and detects false detection by the detection signal of a sensor that generates a detection signal like a gas sensor (heater heating type) and also generates a false detection signal during the initial stability period at the beginning of energization. The present invention relates to a notification device such as a gas leak alarm that can prevent false alarms caused by signals.

As shown in Fig. 1, this type of conventional gas leak alarm device detects a level detection circuit 2 when the output V _G (A in Fig. 2) of the gas sensor 1 exceeds the alarm level V ₁ .
The output V _D changes from L level to H level, and this H level output activates the alarm circuit 4 via the AND gate 3, and in response to the activation of this alarm circuit 4, the external output circuit 5 is activated. It's getting old. However, when gas sensor 1 detects gas, its output increases and exceeds the alarm level _V1 , and
Even during the initial stable period _T1 at the beginning of energization, the output increases and exceeds the alarm level _V1 , and if this continues, a false alarm will be generated during the initial stable period _T1 . In order to prevent this false alarm, the timer time _T2 is longer than the initial stabilization period _T1 , and the output V _T (C in Figure ₂ ) is at L level during the period from the start of energization until the timer time T2 elapses. Output when the period expires
By the timer circuit 6 which changes V _T to H level,
Initial stabilization period by controlling the opening and closing of AND gate 3
The H level output of the level detection circuit 2 due to the increase in the output of the gas sensor 1 during T ₁ is cut off to prevent false alarms due to the false detection signal of the gas sensor 1, and the level detection circuit is configured based on the detection signal of the gas sensor 1 that has passed through the AND gate 3. An alarm is issued by the H level output of 2 (D in Figure 2).

The above timer time T ₂ is such that the initial stability period T ₁ of the gas sensor 1 is in the range of about 1 minute to 6 minutes,
In order to prevent false alarms from occurring for any gas sensor 1, the maximum time must be set to 6 minutes or more.

In this way, the conventional notification device has a gas sensor 1
Regardless of the length of the initial stability period T ₁ of the gas sensor 1 based on individual characteristic differences, the timer time T ₂ is set to be longer than the longest time until the end of the initial stability period T ₁ of the gas sensor 1 with various characteristics. settings to prevent false alarms (gas leak notification even though no gas leak has occurred) due to false detection signals generated from the gas sensor 1 after power is turned on, no matter what characteristics of the gas sensor 1 is used. I was trying to make it possible.

However, in order to prevent the above false alarm, the timer time _T2 is set long, so gas sensor 1
Even if it is already in a stable state (the state in which the false detection signal has disappeared) due to the characteristics of
There was a problem that it did not become alert until T ₂ had passed, causing a delay in becoming alert.

Therefore, an object of the present invention is to be able to prevent false alarms due to the false detection signal generated from the sensor after power is turned on, and to quickly return to the alert state after the false detection signal disappears and the sensor becomes stable. It is an object of the present invention to provide a notification device that can be migrated.

An embodiment of this invention is shown in FIG. That is, this gas leak alarm includes a level detection circuit 14 that generates a detection output in response to a sensor output equal to or higher than the alarm level, and a timer time that is set short when the detection output of the level detection circuit 14 is not generated. The timer circuit 15 is set to a long time when the detection output of the detection circuit 14 is generated, starts counting when the power is turned on, and maintains that state once the time is up; and the detection output of the level detection circuit 14 and the timer circuit 1.
5, and an alarm circuit 17 that responds to the output of the AND circuit 16, the short timer time of the timer circuit 15 is used to detect pseudo detection of the sensor immediately after the power is turned on. The long timer time of the timer circuit 15 is set to be longer than the time until the signal generation starts and shorter than the time from immediately after the power is turned on until the end of the sensor's pseudo detection signal generation. It is set longer than the time.

In this case, the notification circuit 17 causes the flicker circuit F to respond to the detection output of the level detection circuit 14,
The output of the AND circuit 16 is supplied to the collector of the first transistor Tr ₁ via the light emitting side element of the photocoupler PC, and the output of the flicker circuit F is supplied to the base of the first transistor Tr ₁ . A buzzer is generated by the second transistor Tr ₂ which inverts the collector output of _the first transistor Tr 1.
In addition to intermittent operation of BZ, the photocoupler PC
The light-emitting side element of is operated continuously, and the photocoupler
The external output circuit 18 is continuously operated by the light receiving side element of the PC.

In the above, the level detection circuit 14 is composed of the comparator _CP1 . The timer circuit 15 includes a comparator CP ₂ , resistors R ₁ to R ₅ , R ₇ , and a comparator
It consists of C ₁ and diodes D ₄ and D ₅ . The AND circuit 16 is composed of a resistor R ₆ and a diode D ₂ . The notification circuit 17 includes a flicker circuit F, a visible light emitting diode LED, a transistor Tr ₁ ,
It consists of Tr ₂ , resistors R ₁₂ to R ₁₄ , photocoupler PC, diode D ₆ and buzzer BZ.

To explain in more detail, in this gas leak alarm, from time t ₀ to time t ₁ immediately after energization, the output of the gas sensor is lower than the alarm level, and the output of the level detection comparator CP ₁ is as shown in Fig. 5A. As shown in the figure, it is at L level, and the comparator for the timer
The voltage V _P at the negative input terminal of CP ₂ is as shown in FIG. 5B, V _P =V _P1 =V _F +V _CPL . However, the forward voltage drop of _{the VF} diode _D1 , V _CPL , is the L level output voltage of the comparator _CP1 .

On the other hand, the voltage at the positive input terminal of comparator CP ₂
V _C1 is given as the charging voltage of capacitor C ₁ charged through resistors R ₁ and R ₂ , but at the above time t ₀
to time _t1, the voltage is as shown in Figure 5C.
It is lower than V _P (=V _P1 ). Therefore,
The output of the comparator _CP2 is at L level as shown in FIG. 5D.

Furthermore, since the output of the comparator CP ₁ is at L level, the voltage at the minus input terminal of the flicker comparator CP ₃ is lower than the voltage at the plus input terminal given by the resistors R ₈ and R ₉ .
The output of CP ₃ is at H level, and the visible light emitting diode LED lights up as shown in FIG. 5E to indicate energization. On the other hand, the outputs of the comparators CP ₁ and CP ₂ are both at L level, and the transistors Tr ₁ and CP 2
Both Tr ₂ are in the off state, the buzzer BZ does not sound, the photocoupler PC does not operate, and the external output circuit 18 does not operate.

After time t ₁ , when the output of the gas sensor exceeds the alarm level due to false detection, the output of comparator CP ₁ becomes H level, and the voltage V _P at the negative input terminal of comparator CP ₂ is V _P = V _P2 = V _CC ×R Increases to ₄ /R ₁ + R ₃ + R ₄ . However, R ₂ ≫ _{R 1} , R ₃ , R ₄ ,
The resistance R ₂ is ignored.

On the other hand, the voltage at the positive input terminal of comparator CP ₂
Although V _C1 increases over time, the voltage V _P
(=V _P2 ), the output of the comparator CP ₂ maintains the L level. Voltage V _C1 exceeds voltage V _P1 at time t ₂ during the initial stabilization period of the gas sensor, but
Since V _P =V _P2 , comparator CP ₂ does not change.

Also, since the output of comparator CP ₁ is at H level, comparator CP ₃ flickers (L level output and H level output occur alternately) due to resistors R ₈ to R ₁₁ and capacitor C ₂ , and emits visible light. The diode LED blinks to indicate that the gas sensor is generating a false detection signal. On the other hand, since the output of the comparator CP ₁ is at H level, but the output of comparator CP ₂ is at L level, both transistors Tr ₁ and Tr ₂ are off, and the buzzer BZ and photocoupler PC do not operate.

When the gas sensor becomes stable and its output becomes lower than the alarm level at time _t3 , the output of the comparator _CP1 becomes L level, and V _P =V _P1 . At this time, since V _C1 > V _P1 , the output of comparator CP ₂ immediately becomes H level, and the resistor
Charging current flows into capacitor C ₁ from the midpoint of R ₅ and R ₇ through diode D ₅ , capacitor C ₁ is rapidly charged, voltage V _C1 immediately exceeds voltage V _P2 , and the maximum charging voltage V _C1M (=V _CC ×R ₇ /R ₅ +R ₇ ) is reached. However, R ₂ >>R ₅ and R ₇ .

At this time, since the output of the comparator _CP1 is at L level, the visible light emitting diode LED lights up. On the other hand, since the output of the comparator CP ₂ is at the H level, but the output of the comparator CP ₁ is at the L level, the transistors Tr ₁ and Tr ₂ are both off, and the buzzer BZ and photocoupler PC do not operate.

Between time t ₄ and time t ₅ , when the gas sensor detects gas and the output exceeds the alarm level, the output of comparator CP ₁ becomes H level, comparator CP ₃ flickers, and the visible light emitting diode LED turns on. Flashes to indicate gas detection. Furthermore, since the output of the comparator CP ₂ is also at H level, the collector voltage is supplied to _the transistor Tr ₁ via the light emitting diode of the photocoupler PC, and _the base voltage is supplied to the transistor Tr ₂ . The transistor Tr 2 turns on and off in response to the flicker operation of the LED, which turns the transistor Tr ₂ off and on, causing the buzzer BZ to make an intermittent sound in contrast to the blinking of the visible light emitting diode LED, as shown in Figure 5F, to average out the current consumption. There is. The collector current of transistor Tr ₁ and the base current of transistor Tr ₂ alternately flow through the light-emitting diode of photocoupler PC, so that current flows continuously, and the light-receiving transistor of photocoupler PC is continuously turned on. state, causing the external output circuit 18 to operate continuously.

After time t ₅ , when the gas runs out, the comparator
The output of CP ₁ becomes L level, the visible light emitting diode LED lights up continuously, and the buzzer BZ and photocoupler PC stop operating.

Note that when the gas sensor stabilizes by the time the voltage V _C1 exceeds the voltage V _P1 , the visible light emitting diode LED is already lit at that point, and if gas is added at this time, the visible light emitting diode LED will blink. However, since the timer circuit 15 has not timed up, the buzzer BZ and photocoupler PC do not operate.

In addition, if the gas sensor is in gas at the alarm level or higher at the time of initial energization, the comparator CP ₁ should maintain the H level after time t ₁ until the gas drops below the alarm level, and the voltage V _P should wait at V _P2 . , _the voltage V _C1 rises as shown by the broken line in _{FIG .}
The output becomes H level, and the buzzer starts from this moment.
BZ and photocoupler PC operate, and voltage V _C1 is charged to voltage V _C1M . However, V _C1M satisfies the following formula.

V _C1M > V _CC × R ₃ + R ₄ / R ₃ + R ₄ + R ₁ By appropriately selecting this voltage V _C1M and the ratio of R ₁ : (R ₃ + R ₄ ), a capacitor C ₁ with a low withstand voltage can be selected. You can choose. Therefore, a relatively low value can be selected for the resistance _R2 , so
It is resistant to leakage current from capacitor _C1 , has a stable timer time, and can reduce the cost of capacitor _C1 .

R ₆ , R ₁₂ to R ₁₄ are resistors, D ₃ is a diode, D ₆ is a diode for correcting the forward voltage drop of diode D ₂ , and D ₄ is a diode for discharging the capacitor C ₁ when the power is turned off.

As a result of this configuration, it is possible to prevent false alarms due to the false detection signal generated from the sensor after the power is turned on, and moreover, it is possible to quickly shift to the alert state after the false detection signal disappears and the sensor becomes stable. Can be done.

In addition, as shown in Fig. 3, another conventional gas leak alarm device uses the
The alarm flicker circuit 7 is activated by the output of the AND gate 3.
The output of the alarm flicker circuit 7 turns the transistor 8 on and off, and the buzzer 9 is activated.
is beeping intermittently. However, since a continuous signal is required as a signal to be applied to the external output circuit 5, the voltage across the buzzer 9 is smoothed by a resistor 10 and a capacitor 11, and this smoothed voltage is applied to the transistor 13 via a resistor 12. 13 is kept on continuously.

However, such a configuration requires circuits (10 to 13) for converting flicker signals into continuous signals, resulting in an increase in the number of parts and an increase in cost.

Also, the DC signal to be applied to the external output circuit 5 can be taken from the AND gate 3, but in this case,
It is necessary to separate the signal supplied to the alarm flicker circuit 7 by a logic circuit or the like, which poses a problem of increasing the number of parts and increasing costs.

However, in the above embodiment, the flicker signal that causes the buzzer BZ to operate intermittently and the DC signal that causes the external output circuit 18 to operate continuously can be separated only by the photocoupler PC, and the number of parts is small and the cost is low.

As described above, the notification device of the present invention includes a level detection circuit that generates a detection output in response to a sensor output equal to or higher than the notification level, and a timer time that is set short when the detection output of the level detection circuit is not generated. and a timer circuit that sets the timer time to a long time when the detection output is generated, starts timing when the power is turned on, and holds that state once the time has expired, and a detection output of the level detection circuit and a time-up output of the timer circuit. It is equipped with an AND circuit that takes an AND circuit, and an alarm circuit that responds to the output of this AND circuit, and the short timer time of the timer circuit is longer than the time from immediately after the power is turned on until the sensor starts generating a pseudo detection signal, and when the power supply is turned on. The long timer time of the timer circuit is set to be longer than the time from immediately after the power is turned on until the end of generating the pseudo detection signal of the sensor, so that after the power is turned on, It is possible to prevent false alarms due to false detection signals generated from the sensor, and moreover, it is possible to quickly shift to the alert state after the false detection signal disappears and the sensor is in a stable state.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional gas leak alarm.
2A to 2D are signal waveform diagrams of each part, FIG. 3 is a block diagram of another conventional gas leak alarm, and FIG. 4 is a circuit diagram of a gas leak alarm according to an embodiment of the present invention. 5A to 5G are waveform diagrams of each part. 14...Level detection circuit, 15...Timer circuit, 1
6...AND circuit, 17...Notification circuit, 18...External output circuit, F...flicker circuit, _Tr1 , _Tr2 ...transistor, PC...photocoupler.

Claims (1)

[Claims] 1. A level detection circuit that generates a detection output in response to a sensor output equal to or higher than a notification level, and a timer time is set short when the detection output of this level detection circuit is not generated, and the timer time is set short and the detection output is A timer circuit in which the timer time is set to a long time at the time of occurrence, starts counting when the power is turned on, and maintains that state once the time has expired, and the detection output of the level detection circuit and the time-up output of the timer circuit are ANDed together. It comprises an AND circuit and an alarm circuit that responds to the output of the AND circuit, and the short timer time of the timer circuit is set to be longer than the time from immediately after the power is turned on until the sensor starts generating a pseudo detection signal, and from immediately after the power is turned on. Set it shorter than the time it takes for the sensor to finish generating the pseudo detection signal,
The notification device wherein the long timer time of the timer circuit is set to be longer than the time from immediately after the power is turned on until the generation of the pseudo detection signal by the sensor ends. 2. The notification circuit causes a flicker circuit to respond to the detection output of the level detection circuit, supplies the output of the AND circuit to the collector of the first transistor via the light-emitting side element of the photocoupler, and outputs the output of the flicker circuit. is supplied to the base of the first transistor, and a second transistor which inverts the collector output of the first transistor causes the alarm to operate intermittently and at the same time causes the light emitting side element of the photocoupler to operate continuously. 2. The notification device according to claim 1, wherein the external output circuit is continuously operated by the light-receiving element.