JPH04476Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a gas leak alarm.

FIG. 1 shows a circuit diagram of a conventional gas leak alarm. In Figure 1, E is an AC power supply, T is a power transformer, D ₁ is a rectifier diode in the external output circuit, C ₁ is a smoothing capacitor, D ₂ to D ₄ are rectifier diodes in the main circuit, and C ₂ is a smoothing capacitor. , GS is a gas sensing element.

1 is a comparison circuit that compares a signal voltage corresponding to the gas concentration detected by the gas sensing element GS with a threshold voltage. The signal voltage is obtained by dividing the voltage of AC power supply E by gas detection element GS and resistors R ₄ to _{R 8} , rectifying and smoothing this divided voltage with diode D ₆ and capacitor C ₃ , and the threshold voltage is , the main circuit power supply voltage is obtained by dividing it with resistors R ₉ to R ₁₁ , variable resistor VR, and temperature compensation thermistor Th, and these are compared with comparator CP _3. When the signal voltage is larger, The output of comparator CP ₃ becomes high level. _R34 is a feedback resistor and _D7 is a diode.

A delay circuit 2 delays the output of the comparison circuit 1 by about 30 seconds, and is composed of resistors _R12 to _R14 , a diode _D12 , and a capacitor _C4 .

3 is a comparison circuit that prevents false alarms due to noise in combination with the delay circuit 2 by comparing the output of the delay circuit ₂ with the reference voltage.
It is composed of R ₃₅ and R ₃₆ , and when the output of the delay circuit 2 exceeds the reference voltage, the output of the comparator CP ₂ becomes high level.

4 is a timer circuit that responds to the output of the comparison circuit 3, and includes a comparator CP ₁ , resistors R ₁₅ to R ₁₉ , R ₂₁ ,
It is composed of R ₃₃ , capacitor C ₅ and diodes D ₉ and D ₁₀ , and is output when the voltage of capacitor C ₅ charged through resistors R ₁₅ and R ₁₈ exceeds the voltage at the connection point of resistors R ₁₆ and R ₁₇ . becomes high level, and accordingly capacitor C ₅ is rapidly charged through resistor R ₁₉ , and the voltage of capacitor C ₅ rises rapidly. resistance
Since the diode D ₈ is connected, the voltage at the connection point of R ₁₆ and R ₁₇ becomes low when the output of the comparator CP ₂ is low level, and becomes high when the output of the comparator CP 2 is high level. When the voltage at the connection point is a low value, the output of the comparator CP ₁ changes from low level to high level approximately 90 seconds after power is turned on. This timer circuit 4 is for preventing initial ringing, and is set to about 90 seconds, taking into account the rise time and delay time of the gas sensor GS.

Reference numeral 5 designates a flicker circuit in which the output changes periodically between high and low levels when the output of comparator circuit 1 is at high level, and maintains the output at high level when the output of comparator circuit 2 is at low level. ,comparator
It consists of CP ₄ , resistors R ₂₂ to R ₂₅ and capacitor C ₆ , and the inverting input terminal of comparator CP ₄ is a diode.
Connected to the output of comparator CP ₃ via D ₁₄ .

6 is a display circuit consisting of a light emitting diode LED and a current limiting resistor _R26 , which blinks or lights up according to the output of the flicker circuit 5.

7 is the alarm circuit, buzzer BZ, transistor
It consists of Tr ₃ , resistors R ₃₀ , R ₃₁ and diode D ₁₃ .

8 is an alarm drive circuit, which includes transistors Tr ₄ and Tr ₅
and resistors _R27 , _R28 , _R29 , and _R38 , and the first
The input terminal of is connected to the output terminal of the comparator CP ₁ via the resistor R ₂₀ and to the output terminal of the comparator CP ₂ via the diode D ₁₁ , and the second
is connected to the output terminal of the comparator _CP4 , and when the output of the comparator CP2 of the comparison circuit 2 is at a _high level and the output of the comparator _CP1 of the timer circuit 4 is at a high level, the alarm circuit 7 is connected to the flicker circuit 5. It sounds intermittently depending on the output.

9 is an external output circuit, which includes transistors Tr ₁ , Tr ₂ ,
Zener diode ZD ₁ , ZD ₂ , ZD ₃ , resistor R ₁ ~
A zener diode ZD ₃ and a photocoupler are connected to the output terminal of the comparator CP ₁ via _a resistor _{R 37} .
A series circuit of the light emitting elements of the PC is connected, and the above series circuit is connected to the output terminal of the comparator CP ₃ via a diode D ₁₅ , and the comparator of the comparator circuit 1
Output of CP ₃ and comparator of timer circuit 4
When the outputs of CP ₁ both reach a high level, the light emitting element of the photocoupler PC emits light and the light receiving element turns on, turning on the transistor Tr ₁ , which causes the transistor Tr ₁ , the Zener diode ZD ₁ ,
A constant voltage circuit consisting of ZD ₂ , resistors R ₁ , R ₃ and capacitor C ₇ operates to output a constant voltage between terminals V ₀ + and V ₀ -.

Note that _R32 is a variable resistor.

FIGS. 2A to 2H show signal waveform diagrams of each part of the gas leak alarm. The operation will be explained below based on this.

When the power is turned on, the gas sensing element GS is energized and heated, but during the unstable period at the start of energization, the signal voltage _Vs from the gas sensing element GS rises as shown in Figure 2A. The threshold voltage V _r is exceeded, and the output of the comparator CP ₃ becomes high level as shown in FIG. 2B.

Therefore, as shown in FIG. 2C, the non-inverting input voltage V _p2 of the comparator CP ₂ of the comparator circuit 3 exceeds the inverting input voltage V _M2 with a delay of about 30 seconds from the rise of the output of the comparator CP ₃ . Comparator _CP2 produces a high level output as shown in FIG. 2D during the period when non-inverting input voltage V _P2 is higher.

The non-inverting input voltage V _P1 of comparator CP ₁ is the second
As shown in Figure E, the inverted input voltage V _M1 gradually increases after the power is turned on, and is at a low level during the period when the output of the comparator CP ₂ is at a low level, and is at a high level only when the output from the comparator CP ₂ is at a high level. At this time, since the non-inverting input voltage V _P1 is lower, the output of the comparator _CP1 is at a low level as shown in FIG. 2F.

As shown in FIG. 2G, the light-emitting diode LED is in a lighting state immediately after power is turned on, but when the output of the comparator CP ₃ becomes high level, the flicker circuit 5 is activated and the light-emitting diode LED blinks. In the alarm circuit 7, since the output of the comparator _CP1 of the timer circuit 4 is at a low level, the alarm drive circuit 8 is not activated, and even if the flicker circuit 5 is activated as shown in FIG. 2H, the alarm circuit 7 does not sound.

After that, when the state of the gas sensing element GS becomes stable,
The signal voltage V _s will be less than the threshold voltage V _r ,
The output of comparator CP ₃ becomes low level. As a result, the operation of the flicker circuit 5 is stopped and the light emitting diode LED is turned on again.

Approximately 90 seconds after the power is turned on, the comparator
The non-inverting input voltage V _P1 of CP ₁ exceeds the low-level inverting input voltage V _M1 as shown in Figure 2E, and the output of comparator CP ₁ goes to a high level as shown in Figure 2F, and its As a result, the non-inverting input voltage V _P1 of the comparator CP ₁ rises rapidly as shown in FIG. 2E.

After that, when the gas detection element GS detects gas,
As shown in Figure 2A, the signal voltage V _S is the threshold voltage V _r
, the output of the comparator CP ₃ goes to a high level as shown in Figure 2B, and about 30 seconds later than the rising time, the non-inverting input voltage V _P2 of the comparator CP ₂ becomes the inverting input voltage as shown in Figure 2C. Beyond V _M2 , the second
As shown in Figure D, the output of comparator _CP2 becomes high level. When the output of the comparator CP ₃ becomes high level, the flicker circuit 5 is activated and the light emitting diode LED blinks as shown in Fig. 2G.
Since the output of the timer circuit 4 is at a high level and the output of the comparator CP ₂ is at a high level, the alarm drive circuit 8 is activated and the alarm circuit 7 is activated as shown in FIG. 2H based on the output of the flicker circuit 5. beeps intermittently.

However, such conventional gas leak alarms
If the signal voltage _{V s} rises as shown by the broken line in Figure 2A by turning on the gas immediately after the unstable period after the power is turned on and exceeds the threshold voltage V _r , the comparator The output of CP ₃ becomes high level as shown by the broken line in FIG. 2B, and the output of comparator CP ₂ also becomes high level with a delay of about 30 seconds as shown by the broken line in FIG. 2D. As a result, before the output of the comparator CP ₁ becomes high level, the inverted input voltage V _M1 of the comparator _{CP 1} becomes high level as shown by the broken line in FIG _. It takes about 8 minutes from the time the power is turned on to exceed this time, and while the light emitting diode LED immediately goes into a blinking state, the alarm circuit 7 does not operate until about 8 minutes have elapsed from the time the power is turned on.

In this way, in the conventional example, the timer circuit 4
However, when the gas sensor GS stabilized, the light-emitting diode LED switched to the lighting state indicating the monitoring state, which was inconvenient. This is the same state as when the power is turned on in gas.

Therefore, an object of this invention is to provide a gas leak alarm that can match the lighting state of a display indicating the monitored state with the actual monitored state.

FIG. 3 shows a circuit diagram of a main part of a gas leak alarm according to an embodiment of this invention. In Fig. 3, the cathode of the diode _D8 is connected to the output terminal of the comparator CP ₃ instead of the output terminal of the comparator CP ₂ , and the inverted input voltage V _p1 of the comparator CP ₁ changes according to the output of the comparator CP ₃ . That's what I do. Also, instead of connecting the output terminal of the comparator CP ₃ and the inverting input terminal of the comparator CP ₄ with the diode D ₁₄ , the output terminal of the comparator CP ₁ and the inverting input terminal of the comparator CP ₄ are connected by a resistor R ₃₇ and a diode. D ₁₆ , D ₁₇ are connected through the transistor Q ₂ , and when the output of the comparator CP ₁ is at a low level, the transistor Q ₂ is turned off to operate the flicker circuit 5, and when the output of the comparator CP ₁ is at a high level, the flicker circuit 5 is activated. The operation of the flicker circuit 5 is then stopped. Also, connect the output end of comparator CP ₃ to the base of transistor Q ₁ , and
The collector of Q ₁ is connected to the output of comparator CP ₁ . Further, the light emitting element of the photocoupler PC is connected to the emitter side of the transistor _Q1 , so that the light emitting element of the photocoupler PC lights up when the outputs of the comparators _CP1 and _CP3 are both at a high level. R ₄₀ and R ₄₁ are resistors.

The other configurations are the same as in FIG. 1.

Next, the operation of this embodiment will be explained based on FIG. 4.

When the power is turned on, the gas sensing element GS is energized and heated, but during the unstable period at the start of energization, the signal V _s from the gas sensing element GS
exceeds the threshold voltage V _r as shown in Figure 4A,
The output of comparator _CP3 becomes high level as shown in FIG. 4B.

Therefore, the non-inverting input voltage V _p2 of the comparator CP ₂ is equal to the voltage V p2 of the comparator CP ₃ as shown in FIG. 4C.
The inverted input voltage is approximately 30 seconds later than the rise of the output.
V _M2 is exceeded, and the output of the comparator CP ₂ becomes high level as shown in FIG. 4D during a period when the non-inverting input voltage V _P2 is higher.

The non-inverting input voltage V _{P1 of the comparator CP 1 gradually} increases after the power is turned on as shown in FIG. The output of the comparator CP ₃ is at a high level only during the period when the output is at a high level, and since the non-inverting input voltage V _P1 is lower at this time, the output of the comparator CP ₁ is at a low level as shown in Figure 4F. .

In the light emitting diode LED, the output of the comparator CP ₁ is at a low level immediately after the power is turned on, so the transistor Q ₂ is off and the flicker circuit 5 is activated as shown in Figure 4G, regardless of the output of the comparator CP ₃ . It's blinking. Since the timer circuit 4 is at a low level, the alarm circuit 7 does not operate the alarm drive circuit 8, and does not ring even if the flicker circuit 5 operates as shown in FIG. 4H.

After that, when the state of the gas sensing element GS becomes stable,
The signal voltage V _s will be less than the threshold voltage V _r ,
The output of the comparator CP ₃ is at a low level, but since the output of the comparator CP ₁ is at a low level, the transistor Q ₂ is turned off and the flicker circuit 5 is activated.
The light emitting diode LED continues blinking.

Approximately 90 seconds after the power is turned on, the comparator
The non-inverting input voltage V _P1 of CP ₁ exceeds the low level inverting input voltage V _M1 as shown in FIG. 4E, and the output of the comparator CP ₁ becomes high level as shown in FIG. 4F. As a result, the comparator
The non-inverting input voltage V _P1 of CP ₁ rises rapidly as shown in FIG. 4E. As a result, the transistor _Q2 is turned on, the operation of the flicker circuit 5 is stopped for the first time after the power is turned on, and the light emitting diode LED is turned on, indicating the monitoring state.

After that, when the gas detection element GS detects gas,
The signal voltage V _s exceeds the threshold voltage V _r , the output of the comparator CP ₃ becomes high level, and about 30 seconds later than the rising time, the non-inverting input voltage V _P2 of the comparator CP ₂ exceeds the inverting input voltage V _M2 . The output of comparator CP ₂ becomes high level.

When the output of the comparator CP ₃ becomes high level, the transistor Q ₁ is turned on and the light emitting element of the photocoupler PC is turned on, and the transistor Q ₂ is turned off and the flicker circuit 5 is activated.
Light emitting diode LED flashes. Also, since the output of comparator CP ₁ is at a high level,
When the output of the comparator CP ₂ becomes a high level, the alarm drive circuit 8 is activated and the alarm circuit 7 is made to sound intermittently based on the output of the flicker circuit 5.

In this way, in this embodiment, since the output of the timer circuit 4 controls the activation/deactivation of the flicker circuit 5, it is possible to match the monitoring status display by lighting the light emitting diode LED with the actual monitoring status. I can do it. In addition, since the initial energization noise is prevented with linearity, the monitor state can be reached quickly. Also,
It is highly reliable because it prevents initial ringing by following the output of the gas sensor GS.

As mentioned above, the gas leak alarm of this invention is
A gas sensor, a comparison circuit that compares the output of this gas sensor with a threshold value, a timer circuit to prevent initial ringing that times out after a certain period of time has passed after the power is turned on, and a gas sensor that compares the output of this timer circuit with a threshold value. a flicker circuit that operates in response to each of the detection outputs; a display that blinks when the flicker circuit is activated and lights when it is not activated; Since it is equipped with an alarm circuit that sounds when a gas detection output is applied, the flicker circuit is configured to operate in response to each of the timer circuit's timing output and the comparison circuit's gas detection output, and a display. The display is configured so that it flashes when the flicker circuit is activated and lights up when it is not activated, so the display flashes during the initial stop period when the timer circuit is measuring time
The display for the monitoring period after the timer circuit completes timing can be lit continuously, and the display can be flashed when a gas leak alarm occurs, making it possible to match the monitoring status indicated by the lighting of the display with the actual monitoring status. At the same time, the alarm circuit sounds when a gas leak alarm occurs, and a single display indicates whether the gas leak alarm is currently in the initial sound stop period, monitoring period, or gas leak alarm. Can be clearly distinguished and communicated.

Moreover, since the display is lit during the monitoring period, the display indicates that the gas leak alarm is normally energized and is in the monitoring state. Therefore, it is possible to prevent an explosion accident from occurring without noticing a gas leak.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional gas leak alarm;
Figures A to H are waveform diagrams of each part, Figure 3 is a circuit diagram of a main part of an embodiment of this invention, and Figures A to H are waveform diagrams of each part. 1... Comparison circuit, 2... Delay circuit, 3... Comparison circuit, 4... Timer circuit, 5... Flicker circuit,
6...Display circuit, 7...Alarm circuit, 8...Alarm drive circuit, GS...Gas sensor.

Claims (1)

[Scope of utility model registration request] A gas sensor, a comparison circuit that compares the output of this gas sensor with a threshold value, a timer circuit to prevent initial ringing that times out after a certain period of time has passed after the power is turned on, and a gas sensor that compares the output of this timer circuit with a threshold value. a flicker circuit that operates in response to each of the detection outputs; a display that blinks when the flicker circuit is activated and lights when it is not activated; A gas leak alarm equipped with an alarm circuit that sounds when a gas detection output is applied.