JPS6224135A - Gas alarm - Google Patents

Abstract

PURPOSE:To obtain a function effective both for gas leakage and CO poisoning at a low cost, by using only one semiconductor gas sensor. CONSTITUTION:A voltage is applied separately to a plate electrode 1a and a heater 1b of a semiconductor type gas sensor 1 to heat the sensor 1 to a proper temperature for the detection of a CO gas. Outputs X and Y of a timer circuit 11 are applied to an alarm delay circuit 14 and a pulse train the generat ed at the hotput Z of the circuit 14 accordingly. When a gas is detected, the output X or those Y and Z moves to L simultaneously and in turn, the outputs of NOR circuits 13a and 13b go to H. So, R-SFFs 13c and 13d to which these outputs are applied are set and the outputs Q and inversion of Q thereof turn to H from L and to L from H respectively. As a result, transistors (TR) 19 and 10 are turned ON with the rising of the output Q to H from L and indicators 18 and 20 turned ON. With the falling of the output Q to L from H, the output of a circuit 13k moves to H from L to turn ON a TR 17 and a buzzer 16 sounds.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a gas alarm.

[Conventional technology]

Traditionally, gas alarms detect flammable gases such as methane and hydrogen, which are the main components of city gas, and warn in advance of explosions and fires caused by gas leaks; and - detect carbon oxides to warn of oxygen deficiency. Some systems provide advance warning of CO poisoning accidents due to incomplete combustion, etc.

As the sensor for the above-mentioned combustible gas alarm, in addition to a catalytic combustion type in which a precious metal catalyst is supported on a platinum coil, a semiconductor type mainly made of tin oxide is used.As the sensor for the above-mentioned CO gas alarm, In addition to those designed to capture the carbon monoxide electrolytic current in the electrolyte, there are also sensors in which the above-mentioned semiconductor type sensor is heated at a low temperature of around 100°C to make it selectively sensitive only to carbon monoxide. was.

[Problem that the invention seeks to solve]

Each of the above-mentioned sensors detects different types of gas, and those that detect methane and hydrogen have extremely low sensitivity to carbon monoxide, while the opposite sensors are sensitive only to carbon monoxide. There is.

Therefore, in order to issue warnings for both explosions and fires caused by gas leaks and CO poisoning accidents, two units each with built-in gas leak detection sensors and defined carbon detection sensors that operate separately are required. There is no choice but to install alarms side by side or to integrate them into an alarm device with two built-in sensors, which is expensive in terms of cost.

[Means for solving problems]

In view of the above-mentioned problems with the conventional devices, the present invention uses a single sensor to provide a function to detect explosions and fire accidents caused by gas leaks, and a function to detect CO poisoning accidents caused by incomplete combustion due to lack of oxygen. The aim is to provide a gas alarm that achieves this goal by detecting flammable gases such as methane and hydrogen at high temperatures, and detecting flammable gases such as methane and hydrogen at low temperatures. A semiconductor gas sensor having a characteristic of detecting carbon monoxide, a temperature switching means for raising and lowering the temperature of the semiconductor gas sensor in a cycle of a fixed time, and determining the output of the semiconductor gas sensor for each temperature and issuing an alarm. It is characterized by comprising a warning means.

[For production]

In the gas alarm according to the present invention, the temperature of a single semiconductor gas sensor is switched in a cycle of a certain period of time, and the output of the semiconductor gas sensor is determined for each temperature.
Both detection and alarm of combustible gases and -carbon oxide gases detected at both temperatures respectively can be performed and alarmed by a single element.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a gas alarm according to the present invention. In the figure, 1 is a semiconductor gas sensor having a plate electrode la and a heater 1b. The semiconductor gas sensor 1 is made of tin oxide, which is a sensor material that is sensitive to carbon monoxide, and palladium is added as a sensitizer, and it can be used in air or in an atmosphere containing methane, hydrogen, and carbon oxide gas. The temperature-resistance characteristics shown in FIG. 2 are shown in FIG.

Figure 3 (a) shows the output characteristics for each gas concentration when the sensor temperature is 350°C and 120°C.
and mountains).

Now, if the above two temperatures are alternately repeated by changing the voltage applied to the heater 1b and the voltage of the plate electrode 1a is also changed at the same time, the output will be as shown in Fig. 4 in each atmosphere. A waveform is obtained.

In other words, when there is no gas, it is called air sensitivity, and high temperature,
Both values show low values at low temperatures. When methane gas is introduced here, dissociative adsorption occurs on the sensor surface only when the temperature is high, resulting in a large output, and when the temperature returns to low, there is almost no output. - If carbon oxide gas were to flow in, the output would gradually increase at low temperatures, then immediately after switching to high temperatures, the output would transiently increase and then decrease, and after exhausting, the air sensitivity would decrease in one cycle. Return to pattern.

2 is a first power supply circuit that outputs a 100■ DC voltage obtained by half-wave rectifying the commercial AC power supply AC with a diode 2a, smoothing it with a capacitor 2b, and then stabilizing the voltage with a transistor 2C1, a resistor 2d, and a Zener diode 2e. , 3 is 100■ Commercial AC power source is stepped down with transformer T and 2
Next volume'! The AC voltage obtained from IAL + is full-wave rectified by a diode bridge 3a, smoothed by a capacitor 3b, and output as a DC power supply voltage element B for another circuit, and the DC voltage is stabilized by a voltage stabilization circuit 3C. This is a second power supply circuit that outputs a DC voltage of 9V, and the second power supply circuit indicates that the circuit is working normally by lighting up a power indicator 3d consisting of an LED.

4 is a changeover switch for changing the plate electrode voltage of sensor 1; the normally closed contact No. receives the output of power supply circuit 2, the normally closed contact NG receives the output of power supply circuit 3, and the common contact CC receives the plate electrode voltage of sensor 1. One end of the electrode 1a and one end of the heater 1b are connected to each other, and a common contact CC of the switch 4 is connected to one end of the heater 1b.
When the common contact CC of the switch 4 is on the side opposite to that shown in the figure, a voltage of 100 V is applied to the plate electrode 1 of the sensor 1.
A plate voltage switching circuit is configured to apply each voltage to one side of a.

5 is a normally open on/off switch, 6 is a resistor connected in parallel with the switch 5, and the parallel circuit is a secondary winding of a transformer T to which the end of the heater 1b of the sensor 1 is connected. is connected between the other end of the switch 5 and the other end of the heater 1b of the sensor 1, and applies an AC voltage of 1.1■ when the switch 5 is closed and 0.1■ when the switch 5 is opened to the heater Ib. Configure a switching circuit.

The above-mentioned changeover switch 4 and on/off switch 5 are formed by relay contacts, and are controlled by energizing and cutting off energization to a relay coil, which will be described later.

7 is a relay coil, with a resistance of 8, N between 10B and ground.
They are connected through PN l-transistors 9, and are energized when the transistors 9 are turned on and cut off when the transistors 9 are turned off. 10 is i[! of relay coil 7 This is a relay operation indicator consisting of an LED that lights up when the power is on.

1) is a timer circuit, and its two outputs X and Y are
As shown in Figures 5(a) and (b), pulse trains of opposite polarity are sent out, and the pulse train sent to one output The pulse train sent out is 50 seconds - bells, 70
It becomes L level for a second. The output X is connected to the base of the transistor 9 via a resistor. As a result, the transistor 9 repeats a cycle of being off for 50 seconds and on for 70 seconds, and as the transistor 9 turns on and off, the relay coil 7 is intermittently energized, the switch 4.5 is switched, and the heater lb is turned on for 50 seconds. 0. L V, 70
A voltage of 1.1 cm/s is applied to the plate electrode 1a for 50 seconds 9
(2) A voltage of 1oovi is applied for 70 seconds.

12 is a detection circuit, which includes a first detection resistor 12a connected between the other plate electrode 1a of the sensor 1 and the ground, and a second series-connected second detection resistor 12a connected in parallel to the first detection resistor 12a.
and third detection resistors 12b and 12G. 1st
A variable resistor 12 (I) is connected in parallel to the third detection resistor 12a, and a variable resistor 12e is connected in parallel to the third detection resistor 12c. The movable element 12e is connected to the single force of the comparator 12f2 via the analog switch 12g.The divided voltage of the comparators 12f+ and 12ft is connected to the reference voltage by the divided voltages of the resistors 12h, 12i, 12j and 12k. Er+sEr.

(Er+>Erg), and the reference voltage is compared with the voltage of the movable elements of the variable resistors 12d and 12C in the comparators 12fl and 12fZ. The outputs of the comparators L2f and 12g are respectively connected to the inputs of the AND circuit 121, and when the voltage of the mover of the variable resistors 12d and 12e is smaller than the reference voltage, the outputs of the comparators L2f and 12g are connected to the inputs of the AND circuit 121.
, 12g becomes H level, AND circuit 121
The output is at H level.

As described above, when the concentration of combustible gas or carbon oxide gas exceeds a predetermined value and the resistance value between the plate electrodes 13 of the semiconductor gas sensor 1 decreases, the detection circuit 12 detects that the other plate electrode 1a Detection resistors 12a, 12b
Since the voltage at the connection point a between the comparator 12' and
The output of 1 or 12fZ goes from H to L level, AND
The output of the circuit 121 also changes from H level to L level accordingly.

Note that the analog switch 12g above is a timer circuit 1)
When the output Y is at H level, that is, the heater 1b of the semiconductor gas sensor 1
The variable resistor 12 is turned on when a low voltage is applied to the variable resistor 12.
Applying the voltage of the mover e to the single power of the comparator 12f2,
When the output Y73 of timer circuit 1) is < L level,
That is, the heater 1b of the semiconductor gas sensor 1 is turned off when a high voltage is applied, so that the voltage of the mover of the variable resistor 12e is not applied to the comparator 12f2. This prevents the comparator 12f2 from malfunctioning due to the voltage at the connection point a becoming high even when no gas is detected when a high voltage is being applied to the heater.

13 is a switching operation holding circuit that holds the result detected by the detection circuit 12 until the next cycle; the output of the detection circuit 12, that is, the output of the AND circuit 12N is the first input; , X is the second input,
NOR circuits 13a and 13b to which the output Z of the alarm delay circuit 14, which will be described later, is applied to the third input, respectively;
An R-S flip-flop 13C913 in which the outputs of the OR circuits 13a and 13b are input to the set input S, respectively.
d, and the outputs Y and X of the timer circuit 1) are input to the first input,
NOR circuits 13e each have a second input connected to the output Z of the alarm delay circuit 14;

13f, and differentiating circuits 13g and 13h provided between the NOR circuits 13e and 13f and the reset manual power R of the R-S flip-flops 13c and 13d, and one input of the differential circuits 13g and 13h provided through the diodes 13it and 13J, respectively. A NOR circuit 13 is connected to the output 0 of the flip-flops L3c and 13d and is pulled up by a power supply through a resistor, and the other input is connected to the output of an initial delay circuit 15, which will be described later. R-S flip-flop 13c, 1
The output of the initial delay circuit 15 is also connected to the reset manual power R of 3d.

The alarm delay circuit 14 has differentiating circuits 14a and 14b that respectively differentiate the rising edge of the pulse train applied from the outputs X and Y of the timer circuit 1), and the differentiating circuit 14a,
An inverter 14C to which the output of the inverter 14b is input, a resistor 14d and a capacitor 14e connected between the output of the inverter 14C and the + power supply and ground, respectively, and an inverter 14g connected to the output of the inverter 14c via a resistor 14f. The output Z of the inverter 14g is a pulse train as shown in FIG. 5(C), which is at the opening/closing level for 30 seconds every time the pulse train of the outputs X and Y of the timer circuit 1) rises. The pulse train is applied to the inputs of NOR circuits 13a, 13b, 13e, and 13f as described above, and the outputs of these circuits are held at L level while the pulse train is at H level.

The initial delay circuit 15 includes a resistor 15a and a capacitor 15b connected in series between a power supply and ground, and an inverter 15d connected to the connection point of these through a resistor 15C.
The output of inverter 15d is L when the power is turned off.
goes to H level, and this rise resets the flip-flops 13c and 13d, and after turning on the power, the level goes to H level.
After seconds have passed, it goes from H to L level, and after the power is turned on, it becomes 0.
The output to the NOR circuit 13 is held at L level for 180 seconds.

NOR which is the first output of the switching operation holding circuit 13
The output of the circuit 13 is connected to the base of a transistor 17 connected in series with the buzzer 16 between the power supply and ground;
The output Q of the flip-flop 13c, which is the second output, is a transistor 1 connected in series with a combustible gas alarm indicator 18 consisting of a resistor and an LED between the power supply and ground.
The output Q of the flip-flop 13d, which is the third output, was connected to the base of 9 through a resistor, and the output Q of the flip-flop 13d was connected in series with a defined carbon gas alarm indicator 20 consisting of a resistor and an LED between the power supply and ground. It is connected to the base of transistor 21 via a resistor.

Therefore, when the output of the initial delay circuit 15 is at L level, the flip-flop 13c is turned on, and its output Q,
When Q reaches H and L levels respectively, the output to the NOR circuit 13 becomes H level, turning on the transistor 17 and sounding the buzzer 16, and turning on the transistor 19 and lighting the indicator 18, indicating that the concentration is higher than the predetermined concentration. An alarm is issued when flammable gas is detected. On the other hand, the flip-flop 13d is set and its outputs Q and Q are respectively H.
, when the output to the NOR circuit 13 becomes H level, the buzzer 16 sounds, the transistor 21 is turned on, the indicator 20 is lit, and the defined carbon gas with a predetermined concentration or higher is detected. An alert will be issued when the

Note that the outputs of the initial delay circuit 15 are also connected to the bases of the transistors 19 and 20 through resistors, so the transistor 19 is kept off for 180 seconds after the power is turned on, and when unstable immediately after the power is turned on, This prevents erroneous instructions.

In the above configuration, when the power is turned on, the voltage of the output terminal B of the second power supply circuit 3 immediately rises in response to this, the circuit operation of each part is started, and the timer circuit 1) outputs its output X, A pulse train as shown in FIG. 5 (al, (bl) is sent to Y. When the outputs The relay coil 7 is not energized, and the switches 4 and 5 consisting of relay contacts are in the state shown in the figure.Therefore, the plate electrode 1a of the semiconductor gas sensor 1 receives a DC voltage of 9V, and the heater 1b receives a voltage of 0. ．．
A voltage of 1V is applied to each semiconductor gas sensor 1.
The temperature is approximately 120℃, which is suitable for detecting defined carbon gas.
heated to a temperature of

Further, the output Y of the timer circuit 1) is applied to the analog switch 12g of the detection circuit 12, and controls the analog switch 12g to be turned off when the output Y is at L level and turned on when it is at H level. Therefore, when a high voltage is applied to the heater 1b of the semiconductor gas sensor 1 and the heater 1b is in a high temperature state, the comparator 12fz is overpowered and the voltage at point a is compared with the reference voltage Er+ at the comparator 12ft. , on the other hand, when the semiconductor gas sensor 1 is in a low temperature state, the voltage at point a is
At point fz, it is compared with both the reference voltages Er, Er2, but the voltage at point a at this time never becomes larger than the reference voltage Er under any circumstances, and the detection circuit 12 The output of the comparator 12f2 becomes dependent on the output of the comparator 12f2.

Furthermore, the outputs X and Y of the timer circuit 1) are output from the alarm delay circuit 1.
4, and in response to this, the output Z of the alarm delay circuit 14
As shown in FIG. 5(C), a pulse train that maintains the H level for about 30 seconds is generated in response to the rise and fall of the outputs X and Y, and this is the output of the detection circuit 12 and the timer circuit 1). The output of

NOR circuit 13a to which Y is applied.

N to which the outputs X and Y of the timer circuit 1) are respectively applied.

It is applied to the inputs of R circuits 13e and 13f, and the NOR
The outputs of the circuits 13a, 13b, 13e, and 13f become H level when all inputs of each circuit become L level.

In the NOR circuits 13a and 13b, the outputs X or Y other than the output of the detection circuit go to the L level synchronously, but the detection circuit 12 does not go to the L level unless it detects a gas with a predetermined concentration or higher. Its output never goes to H level. However, when gas is detected, the outputs X, Y, and Z become L level at the same time, and the NOR circuits 13a and 13
Since the output of B becomes H level, this NOR circuit 13a
.

R-S flip-flops 13c and 13d whose set inputs are applied with the output of RS flip-flop 13b are connected, and their outputs Q and Q go from L to H level and from H to L level, respectively.

When the output Q rises from the L level to the H level due to the setting of the flip-flops 13c and 13d, the transistor 19.21 is turned on and the indicator 18.20 is lit. Further, as the output Q falls from the H level to the L level, the output to the NOR circuit 13 changes from the L level to the H level, and in response, the transistor 17 is turned on and the buzzer 16 sounds. However, at this time, the output of the initial delay circuit 15 must be at L level.

Further, when the outputs X, Y, and Z of the NOR circuits 13e and 13f become L level at the same time, their outputs become H level, which are differentiated by differentiating circuits 13g and 13h, respectively, to obtain differentiated pulses. To illustrate the output of the differentiating circuit 13h, a differential pulse as shown in FIG. 5 (a) is obtained.
3d is applied to the reset input of NOR circuit 13a,
Flip-flop 1 is set by the output of 13b.
Reset 3c and 13d respectively.

As is clear from the figure, since the reset is performed every cycle, a flip-flop that is set once retains its set state until the next cycle. Therefore, even if the output of the detection circuit I3 is temporarily lost until the next cycle due to switching of the heater voltage or the like, the operations of the indicators 18, 20 and the buzzer 16 will be maintained until the next cycle.

For example, when the output X of timer circuit 1) is at L level,
That is, when a low voltage is applied to the heater 1b of the semiconductor type gas sensor 1 and the sensor 1 has sensitivity to -carbon oxide gas, when the semiconductor type gas sensor 1 senses carbon monoxide gas having a predetermined concentration or higher, as shown in FIG. As shown by dl, the power of the comparator 12f2 rises, and in response, its output becomes L level. Then, when the outputs X and Z both reach the L level, the setting force S of the R-S flip-flop 13d rises from the L level to the H level as shown in FIG. The output 0 falls from the H level to the L level as shown in FIG.
6 is operated.

In addition, when flammable gas exists at a predetermined concentration or higher,
When the output Y of the timer circuit 1) is at L level, the comparator i2f+, NOR circuit 13a,
This is performed for the flip-flop 13c, and the buzzer 16 sounds.

In the above embodiment, indicators 18 and 20 are used to distinguish between combustible gas and carbon monoxide gas, but instead of this, the buzzer sound may be changed or the type of gas may be notified by voice. Good too.

Further, in the illustrated embodiment, two comparators are used in the detection circuit, but the same function can be performed using one comparator. In this case, analog switches that are alternately turned on by the outputs X and Y may be provided between the variable resistors 12d and 12e and one comparator.

Furthermore, in the example, the type of detected gas is identified, but the way to deal with the gas depends on the current situation, such as opening a window to introduce fresh air or closing the gas valve. This may not be necessary, as the task will come naturally.

In addition, in the above-mentioned embodiment, gas detection is performed for vaporized alcohol gas at both high and low temperatures.
Both indicators 18 and 20 are lit at the same time as the buzzer sounds.

〔Effect of the invention〕

As explained above, according to the present invention, by using only one semiconductor type gas sensor, it is possible to provide an alarm device effective for both gas leakage and carbon monoxide poisoning at low cost.

In particular, in the preferred embodiment, the unstable output of the semiconductor gas sensor during temperature switching transients is ignored, and the judgment result of the gas sensor is retained until the next cycle, so the problems caused by using a single sensor are eliminated. ing.

In addition, since the warning is made in a manner that allows identification of whether it is caused by high temperature or low temperature, and the gas can also be identified, it is possible to take appropriate measures when the alarm occurs.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the temperature and resistance characteristics of a semiconductor gas sensor for each gas quality, and Fig. 3 is a graph showing the temperature and resistance characteristics of a semiconductor gas sensor at high and low temperatures. Graph showing gas concentration-sensor output characteristics,
FIG. 4 is a waveform diagram showing output changes for each gas when switching the heater voltage of the semiconductor type gas sensor, and FIG. 5 is a diagram showing waveforms at various parts of the circuit in FIG. 1. DESCRIPTION OF SYMBOLS 1... Semiconductor type gas sensor, 2... First power supply circuit, 3... Second power supply circuit, 4... Selector switch, 5
...On/off switch, 7...Relay coil, 1
)...Timer circuit, 12...Detection circuit, 13...
・Operation holding circuit when switching, 14...Alarm delay circuit, 16
...buzzer, 18...flammable gas alarm indicator, 20...-carbon oxide gas alarm indicator. Patent applicant Yazaki Sogyo Co., Ltd. 2nd design degree (0C) Figure 3 (a) (b) Force°°
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Claims (4)

[Claims] (1) Detects flammable gases such as methane and hydrogen at high temperatures,
a semiconductor gas sensor having a characteristic of detecting carbon monoxide at low temperatures; a temperature switching means for raising and lowering the temperature of the semiconductor gas sensor in cycles over a certain period of time; and determining the output of the semiconductor gas sensor for each temperature and generating an alarm. A gas alarm comprising: an alarm means for emitting an alarm. (2) The gas alarm device according to claim (1), wherein the alarm means includes means for ignoring the output of the semiconductor gas sensor during a temperature change transition. (3) The gas alarm device according to claim (1), wherein the alarm means includes means for holding the determination result of the output of the semiconductor gas sensor until the next cycle. (4) The gas alarm device according to claim 1, wherein the alarm means includes means for displaying an alarm for high temperature and low temperature in a distinguishable manner.