JPS622148A - Battery type gas detector - Google Patents

Abstract

PURPOSE:To enable the prevention of possible harzard, by selecting a warning pattern depending on the emergency level of alarm and the residual capacity of a detector battery to display an accurate function. CONSTITUTION:When the density C1 of a gas as measured with a gas detection element 2 exceeds the secondary set reference value CS2 while the battery voltage (e) is above 0.9V a continuous warning pattern is selected; if the voltage is below 0.9V, an intermittent warning pattern D1 is selected. Then, when the density C1 is under the reference value CS2 while the voltage is above 1.1V, a pattern D1 is selected; if the voltage (e) is below 1.1V, an intermittent warning pattern D2 is selected with the warning time relatively less than the pattern D1. When a warning is given based on any of the patterns, manual halting operation is performed by a person hoticing it and thus, this performs an accurate function as gas detector thereby preventing possible hazard.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a battery-powered gas detector that takes a reasonable warning pattern based on the degree of emergency and the remaining capacity of the battery.

[Prior art and its problems]

The target gases for household gas detectors are mostly city gas and LPG. There are various types of gas sensors that detect these gases, but the mainstream ones are those using a catalytic combustion method and those using semiconductors. The former catalytic combustion method has been used for a relatively long time and is excellent as a household product in terms of low cost, ease of handling, reliability, stability, and no maintenance required. This catalytic combustion type gas sensor has a very simple structure consisting of a platinum wire heater coated with a catalyst. A constant current is passed through this element to preheat it to an appropriate temperature. When a target gas, that is, a combustible gas, comes into contact with this, it burns on the catalyst surface and generates combustion heat. Therefore, the temperature of the platinum wire rises and the electrical resistance increases. This change in resistance is extracted as an unbalanced voltage in the bridge circuit. This voltage is proportional to the concentration of the target gas, so gas can be detected. Conventionally, gas detectors have typically been powered by commercial power. 1! If it could be operated in a pond, it would be desirable for general household use, as it would not only require troublesome wiring work, but also would not affect the aesthetics of the room due to the wiring. On the other hand, battery-powered detectors have the following problems: ■ The battery life is short because it consumes power around IW, and the battery has to be replaced frequently, which is inconvenient for maintenance. ■ The battery voltage varies at the beginning and end of use. There were technical problems such as □ that stable performance could not be guaranteed without proper maintenance because the Recently, the following efforts have been made to solve these technical problems. In other words, in order to extend the life of the battery, we first try to consume as little energy as possible. Therefore, this gas detector is not operated all the time, but is operated intermittently. That is, the gas is detected every certain period T, for example, every 2 to 3 minutes, for a short period of time ΔT1, for example, for 10 seconds. Of course, this cycle must be selected carefully depending on the purpose, and the current is not constantly energized during the above-described detection time ΔT, but is energized intermittently. In other words, the detection period Δ
Divide T into two parts. In other words, the first part is for preheating the sensing element (preheating period ΔT), and the second part is for actually measuring, comparing with the set value, and outputting a gas detection signal as necessary ( The measurement period is ΔTa). This first part can achieve its purpose by being energized intermittently. The second portion needs to be continuously energized, although for a relatively short time. Next, in order to eliminate the negative effect on detection accuracy caused by the battery voltage decreasing significantly during the period of use, it is necessary to measure the battery voltage at a certain period, for example every 1 to 2 hours, and adjust the voltage accordingly. change the method of preheating and energizing the sensing element. That is, the ON time of intermittent energization is made to be even. The delicate adjustments of intermittent detection and intermittent energization as described above are
Everything is controlled by a microcomputer, that is, it is controlled by a microcomputer. However, there are some points that are not taken into consideration in the conventional example described above. It is a way of issuing a warning. Since battery energy is used to issue an alarm, consideration must be given to how it is issued. That is, to put it very roughly, the power consumption of continuous alarming by a buzzer is several tens of times the power consumption of continuous detection operation. If a gas is detected when no one is present, it is necessary to continue some sort of warning for a certain amount of time in order to alert the neighbors. In other words, energy saving in terms of alarms is required. In the conventional example, it can be said that there is still room for rationalization in the way batteries are used.

[Purpose of the invention]

The purpose of this invention is to solve the problems of the conventional ones, and to create a reasonable alarm pattern, that is, an alarm signal for as long as possible, depending on the urgency of issuing the alarm and the remaining battery capacity at that time. Our goal is to provide a battery-powered gas detector that is designed to save energy by transmitting and receiving continuous warnings, and to automatically select one that takes into consideration the urgency of the warning.

[Key points of the invention]

The main points of the present invention for achieving the above object are as follows. That is, the method of issuing an alarm, that is, the alarm pattern, is selected based on the urgency of issuing the alarm and the remaining capacity of the battery of the detector at that time. The concentration of the detected gas is used as a measure for determining the degree of urgency, and the battery voltage at that time is used as a measure for the remaining capacity of the battery. As an alarm pattern, for example, in the case of a buzzer,
The most severe one is a continuous sound, and the next level is a continuous sound.
In other words, a moderate alarm is alerted by intermittent tones at short intervals, and a milder alarm is alerted by intermittent tones at longer intervals. The selection operation of the alarm pattern based on the conditions of the degree of urgency and the remaining battery capacity is performed by the microcomputer.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to a circuit diagram partially represented by blocks in FIG. 1 is a battery, and may be a primary battery, a secondary battery, or a battery that can be charged from a commercial power source by providing a charging adapter. 2 is a gas detection element, for example, a platinum wire heater coated with a catalyst; 3 is a compensating element; since the gas detection element 2 is easily affected by changes in ambient temperature, this element is used to counteract this effect. This is an element with low reactivity with gas, which constitutes a bridge circuit in combination with the gas detection element 2. 4.5 is another bridge resistor constituting the bridge circuit. Reference numeral 6 denotes a PNP transistor a that controls the ON-OF@F@ control of energization of the gas detection element 2, and is operated by a command signal from a microcomputer 9, which will be described later. 7a is an inverter that performs signal inversion. 8 is an A/[1 converter, which converts analog signals such as gas detection voltage into digital signals. It performs such control. The well-known microcomputer 9 basically has CPt1. It consists of RAM, ROM, input port, and output port. A program to control the CPU is written in the ROM, and the CPIJ reads required external data from the input port according to this program, or reads the RA? It performs arithmetic processing while exchanging data with l, and outputs the processed data to the output port as necessary. The output port is composed of a latch circuit, receives a 1m electric signal from the output boat, temporarily stores data in that boat, and outputs it to the outside. 10 is a temperature detection element, such as a thermistor, and 12 is a humidity detection element, such as one using lithium chloride. 11.13 is the temperature detection element 10
, are resistors for extracting the resistance change of the humidity detection element 12 as a corresponding voltage output. 22 is a buzzer which is an alarm means for gas detection; 21
is a transistor that operates as a switch depending on the output voltage from the output port. Naturally, the buzzer 22 is powered by the battery 1, which is sourced from the gas detector 1. Note that the buzzer 22 uses, for example, a piezoelectric ceramic diaphragm and has an automatic oscillation circuit built therein. Its features include extremely low power consumption compared to electromagnetic buzzers, and its non-contact structure means it has a semi-permanent lifespan. The main specifications are sound pressure
75 dB/m, driving voltage 5 to 240 CV, current consumption 5 to 15 mA, and operating temperature -10 to +60°C. Next, the operation of this circuit will be described. First, a constant current is passed through a platinum heater coated with a catalyst, which serves as the gas detection element 2, to heat it to a predetermined appropriate temperature. When combustible gas comes into contact with this, it burns on the catalyst surface and generates combustion heat. As a result, the temperature of the platinum wire rises and its electrical resistance increases. This resistance change is detected by a bridge circuit. That is, the gas detection element 2. Compensation element 3゜bridge resistor 4
, 5 is detected as an unbalanced voltage of the bridge circuit. Since this voltage is proportional to the gas concentration, gas detection is possible. Further, this voltage is converted into a digital signal by the A/D converter 8 and then input to the input port of the micro combinator 9 . The function of transistors 6a, 6b, 6c is switching. In other words, the transistor 6a controls the energization to the bridge circuit as a gas detection circuit from 0N-OFF1+IJ.
1 m long, and performs preheating of the gas detection element 2 in the first stage and extraction of the unbalanced voltage as a measurement voltage from the bridge circuit in the second stage, and also uses the transistor 6b.
The transistor 6c applies voltage to the A/D converter 8, the circuit including the temperature detection element 10, and the circuit including the temperature detection element 12, converts the measured voltage from the bridge circuit into a digital signal, and then 1 cycle of battery voltage as described in . It has a function of inputting three elements of ambient temperature and ambient humidity, converting them into digital signals, and inputting them to the microcomputer 9. That is, the battery voltage is taken out from point P on the circuit. Furthermore, since the temperature detector lO1 and the humidity detector 12 are resistors that change depending on the temperature and humidity, the magnitude of the current changes depending on the change in their respective resistance values. Therefore, the voltage across the resistors 11 and 13 connected in series exhibits a value corresponding to temperature and humidity. The timing of the switching operations of the transistors 6a, 6b, and 6c is controlled by the output of the microcomputer 9, as described below. In addition, the inverter 7a.
7b and 7c are transistors 6a, 6b, and 6, respectively.
It has the function of completely inverting the output of the microcomputer 9 and making it the input voltage between the emitter and base of each transistor. Gas detection is not performed constantly as described above, but is performed only for about 10 seconds every 2 to 3 minutes, for example. Most of this sensing operation period is
A period of heating the gas detection element 2 to a certain appropriate constant temperature,
In other words, this is a preheating period, which is performed by intermittent energization. FIG. 2 is a conceptual diagram of the above-mentioned intermittent detection and intermittent AT, expressed as a time chart. That is, FIG. 2 shows how the bridge circuit as the gas detection circuit in the block circuit diagram of FIG. 1 is energized. As shown in FIG. 2(a), the gas detection period is T, and the detection period within it is ΔT, which further includes a preheating period ΔT and a measurement period ΔT4. The situation during this energization period is shown in more detail in the same figure (dl).
In t, the time during which current is actually applied is Δt. This energization time Δt is adjusted by three factors, as will be described later. Next, the state of change in temperature of the gas detection element due to this intermittent energization is shown in the figure (the top of the figure) (C1 is the state of the output voltage as the gas detection signal of the measured result. Fig. 3 shows a conceptual diagram explaining how to select the energization rate for intermittent energization. That is, Fig. 3(a) shows the energization time Δt and the energization period t.
(b)
1 is a relational diagram of both elements regarding how to determine the current conduction rate χ in order to bring the gas detection element to a determined preheating temperature within a determined time with respect to the battery voltage e. In other words, the battery voltage e changes considerably during use; for example, in the case of an ordinary primary battery, it changes by 1.6
~0.9v. Therefore, unless the battery voltage e is measured every 1 to 2 hours and the energization time is controlled according to the measured value, the preheating temperature will not reach the predetermined preheating temperature, resulting in an error in gas detection. The reference curve A is a relationship diagram when the ambient temperature and ambient humidity are in the reference state, and the correction curve A1 is a relation diagram when the ambient temperature and ambient humidity are in the reference state. The correction curve A2 shows cases in which the temperature is lower than the standard, the humidity is higher than the standard, or both cases. In other words, the higher the ambient temperature or the lower the ambient humidity, the easier it is to heat the gas sensing element, and vice versa. In other words, using these correction curves, the time ratio of intermittent energization, that is, the energization rate, is determined based on changes in battery voltage while taking into account the effects of ambient temperature and ambient humidity. This determination procedure is performed by a microcomputer program as described later, based on functional relationships obtained empirically or experimentally. Next, the operation of the microcomputer 9 will be explained in the fourth section.
This will be explained in detail based on the flowchart in the figure. First, I will explain the symbols used. h is the battery voltage e
This counter determines when to detect 1 ambient temperature θ1 ambient humidity W, and is the number of times the gas detection cycle T is repeated. ■
is a counter for determining T to the gas detection period, i is a counter for determining the preheating energization time Δt, and j is the value obtained by subtracting the preheating energization time Δt from the preheating energization period t, that is, a counter for determining the preheating energization stop time. , J is a value obtained by subtracting the detection period ΔT from the detection period T, that is, a counter for determining the detection pause period. Also, H,N. n, m, and M are the initial values of I, t, j, and J, respectively. In conclusion, a instructs to start measuring the gas concentration, ■
C is the measured value of the gas concentration, CI is the gas concentration corrected for the battery voltage, Cll-cs
z is the first and second set reference value of gas concentration, respectively;
(C*I<Cs*). TRa, TRb, and TRc are each transistor 6
These are the abbreviations for a, 6b, and 6c (see Figure 1). Next, we will move on to the explanation of the flowchart. In step S1, h is initialized, and in step S2, TRb and TRc are activated. Next, in step S3, the battery voltage e, the ambient temperature θ
, and the ambient humidity W, and in step S4, the calculation Δt-f(e, θ, W), that is, the calculation formula obtained empirically or experimentally using the above three elements, is used to preheat the gas sensing element. Calculate the energization time Δt. Then, in step S5, TRb and TRc are stopped. The area up to this point is for determining the preheating intermittent energization time Δt. Next, in step S6, 1. J, step S7
Initialize l and j, respectively, and set T in step S8.
Activate Ra to energize the bridge circuit and eventually the gas detection element. Decrement l in step S9,
In step SIO, it is determined whether l has reached the limit (zero), and if YES, in step Sll, TRa is stopped, that is, the gas detection element is de-energized. Next, in steps 512 to 513, the de-energization is stopped. After determining the time and repeating the above-described energization and stopping a predetermined number of times in steps S14 to S515, the process moves to the next step, that is, the measurement stage.Up to this point, the gas detection element is intermittently energized, i.e. MIM<, which specifies the preheating period.Next, in step S16, both TRa and TRb are activated, in step 517, the measured value C of the gas concentration is input, and in step S18, the voltage correction value of this measured value C is used. A certain CI is calculated.In other words, in order to cancel out the effect of decreasing battery voltage, the gas concentration measurement value is corrected based on the battery voltage e measured at the closest time.In step S19, the CI is calculated as follows. It is compared with the secondary setting reference value C0, and if YES, an alarm pattern is selected in steps 820 and S26 and an alarm signal corresponding to the pattern is output.Up to this point, it is the area of measurement and alarm.Of course, in step 519 If NO, there is no need to output an alarm signal, and the process moves directly to the next step 530. Before going into the explanation of the alarm pattern selection operation, let us explain the alarm pattern selection matrix in FIG. 5 (based on al. In Figure 5 (al), the gas concentration levels are shown in the horizontal direction: ■ If the gas concentration is greater than or equal to the second set reference value C0, ■ If the gas concentration is less than the second set reference value C0t, the first set reference value In the case of CS+ or above, take the three cases where the gas concentration is less than the second set reference value C0I.Also, in the case of three battery voltage steps in the vertical direction, fll 1. I
If DCV or more, (2) 1, I Less than DCV 0.
If it is 9DCV or more, if it is less than +310.9DCV□
It is. ■-(1) as a warning pattern. - When (2) is selected, the option is continuous.This choice was made because the gas concentration is higher than the secondary set standard value, the urgency is high, and the remaining capacity of the battery is relatively high. be. Next, ■-(3), ■-(When 11, intermittent alarm D
1, and in the case of ■-(2) and ■-(3), select the intermittent alarm D2, respectively. In addition, ■-+11. (21,431
Naturally, there is no warning when this happens. Figure 5 fbl~(
dl indicates an alarm pattern, and the 5th occurrence) is a continuous sound. The specific pattern of intermittent alarm 01.02 is shown in Figure 5 (C1, fdl), as shown in Figure 5 (C1, fdl), intermittent alarm D1 has a larger proportion of ON time, that is, alarm time, in a certain period than intermittent alarm D2. In other words, it can be said that the intermittent alarm D1 is an alarm pattern that attracts more attention than the intermittent alarm D2.This is based on a comprehensive judgment of the degree of urgency based on the gas concentration and the remaining capacity of the battery. Of course, the one shown in Figure 5 is just one example; various alarm patterns and their selection criteria can be considered. It is also possible to adopt a combination pattern in which the battery voltage level is further subdivided than the example shown in Fig. 5 (al), and the possible alarm time can be further extended. There may be various modifications depending on the installation environment of the gas detector.Now, we return to the operation explanation using the flowchart.First, in step S20, CI>Csz, that is, the gas concentration is the second setting standard. whether it is greater than or equal to the value,
is judged. If YES, it is determined in step 521 whether the battery voltage e is 0.9 DCV or more. If YES, "Continuous alarm pattern" is selected in step S24. Also, step S
If NO in step S21, in step S25,
Select alarm pattern <Dl>. Returning to step S20, if NO, that is, if the gas concentration C1 is less than the first set reference value Csz, it is determined in step S22' whether the battery voltage e is 14 ocv or more. If YES, the alarm pattern <01> in step S25 is selected. Conclusion In step 522, NO, that is, the battery voltage e is 1. ID
If the voltage has decreased below the CV, in step S26, an alarm pattern <D
2> is selected. and step 524.25.2
When an alarm is issued based on any of the patterns 6, the operation is manually terminated by the person who noticed this. On the other hand, retroactively in step 519, if No, that is, the gas concentration is less than the first set reference value, there is no need to issue an alarm, and in step S30, TRa, TR
b is stopped, and in steps 531, 332 a sensing pause period is determined. Subsequently, in steps S33 and S34, the process returns to the stage before step S6, and the next intermittent detection operation is performed again. After the gas detection operation has been performed a predetermined number of times, the process returns to the stage before step S1, and the same process as already described is performed. [Effects of the Invention] Therefore, the present invention has the following excellent effects. (1) Since the method of issuing an alarm that matches the original purpose is selected based on the absolute condition of test gas concentration and the relative condition of battery voltage, it functions more accurately as a gas detector. can do. (2) Even if no one is indoors for a long time, a pattern alarm will be issued that takes into account the remaining battery capacity at that time, so there will be more opportunities for neighbors to notice and prevent danger. It is possible to prevent this. (3) Since the way the warning is issued changes depending on the degree of emergency, there is no risk of causing unnecessary tension or confusion in relatively minor cases. In other words, it will be easier to take action based on knowing the actual situation.

[Brief explanation of drawings]

Figure 1l: Circuit diagram of an embodiment according to the present invention, Figure 2: Conceptual diagram of intermittent detection and intermittent energization, Figure 3: Explanatory diagram of energization rate, Figure 4: Flowchart showing the operation of the microcomputer, Figure 5 Figure: Diagram for explaining alarm pattern selection. 1: Battery, 2: Gas detection element, 3: Compensation element, 9: Microcomputer, 21: Transistor, 22: Alarm buzzer. Atsushi 1 Showa 2 (!) AT pole telegram voltage C 3rd Figure Atsushi 5 mouth

Claims (1)

[Claims] 1) Using a battery as a power source, the gas detection operation is performed intermittently at a predetermined period, and the contact combustion surface between the gas detection element and the gas to be detected is preliminarily brought to a predetermined temperature. gas concentration comparison means that performs heating by intermittent energization and compares the gas concentration detected by the intermittent gas detection operation with a preset gas concentration reference value; a battery voltage comparison means for comparing the detected battery voltage reference value with a battery voltage reference value; 1. A battery-powered gas detector comprising: alarm signal pattern selection means for selecting and determining an alarm signal pattern to be output during a period. 2) A battery-powered gas detector according to claim 1, characterized in that there is one gas concentration reference value. 3) A battery-powered gas detector according to claim 1, characterized in that there are a plurality of gas concentration reference values. 4) A battery-powered gas detector according to any one of claims 1 to 3, characterized in that there is one battery voltage reference value. 5) A battery-powered gas detector according to any one of claims 1 to 3, characterized in that there are a plurality of battery voltage reference values. 6) A battery-powered gas detector according to any one of claims 1 to 5, characterized in that the pattern of the alarm signal consists of a continuous signal and a plurality of types of intermittent signals. . 7) A battery-powered gas detector according to claim 6, characterized in that the type of intermittent signal is based on a difference in time length between intermittent and continuous signals.