JP2004226242A - Water detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an electrolysis amount of water while preventing corrosion of an electrode in a water detector. <P>SOLUTION: This detector is constituted of two electrodes 1, 2 provided under water, a positive pulse generating means 3 and a negative pulse generating means 4 for impressing alternately positive and negative voltages between the two electrodes, an electric continuity detecting means 6 for detecting a current flowing between the two electrodes, and a timer means 7 for driving intermittently and alternately the positive pulse generating means 3 and the negative pulse generating means 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a water detection device that detects the presence or absence of conductive water.
[0002]
[Prior art]
2. Description of the Related Art Some conventional water detection devices detect the presence or absence of water by applying an AC voltage to two electrodes and detecting a flowing current (for example, see Patent Documents 1 and 2). Such a water detection device is often used for a hot water heating boiler. Hot water heating boilers have been used as a central heating heat source to heat the entire house in cold climates. Heating is performed by making hot water with a hot water heating boiler and circulating the hot water through a radiator in each room. In such a system, it is necessary to detect the presence or absence of circulating water in order to prevent the boiler from burning in an empty state, and a water detecting device is provided.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 2-8247 [Patent Document 2]
JP-A-4-125233
[Problems to be solved by the invention]
However, in the above-described conventional water detecting device, although the electrode is prevented from being corroded by applying an alternating current, generation of oxygen gas and hydrogen gas due to electrolysis of water cannot be avoided. When water was electrolyzed to generate gas, circulating water had to be refilled accordingly.
[0005]
An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a water detection device capable of suppressing the electrolysis of water to a very small amount while preventing corrosion of an electrode.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides two electrodes provided in water, a positive pulse generating means for alternately applying a positive and negative voltage between the two electrodes, a negative pulse generating means, It comprises a conduction detecting means for detecting a current flowing between two electrodes, and a timer means for intermittently driving the positive pulse generating means and the negative pulse generating means alternately.
[0007]
According to the invention, since the positive pulse generating means and the negative pulse generating means are alternately driven by the timer means, there is no bias in the potential and the electrode can be prevented from being corroded. Further, since the positive pulse generating means and the negative pulse generating means are intermittently driven by the timer means, it is possible to reduce the current flowing through the electrodes and reduce the amount of Can be suppressed.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 includes two electrodes provided in water, positive pulse generating means for alternately applying positive and negative voltages between the two electrodes, negative pulse generating means, It comprises a conduction detecting means for detecting a current flowing between the electrodes and a timer means for intermittently driving the positive pulse generating means and the negative pulse generating means alternately.
[0009]
Since the positive pulse generating means and the negative pulse generating means are alternately driven by the timer means, there is no bias in the potential and the electrode can be prevented from being corroded. Also, since the positive pulse generating means and the negative pulse generating means are intermittently driven by the timer means, the current flowing through the electrodes can be reduced compared to the case of continuous driving, and the amount of water electrolysis can be reduced. Can be suppressed.
[0010]
According to a second aspect of the present invention, the conduction detecting means is configured to perform the detection at a timing synchronized with the timer means.
[0011]
The conduction detection means can detect the conduction of water only during the period when the current is flowing through the electrodes. However, the time for driving the positive pulse generating means or the negative pulse generating means and the time for stopping the driving are set by the timer means. Per unit current can be reduced. Therefore, if the period during which a current is applied to the electrodes is shortened in order to suppress the amount of water electrolysis, it becomes difficult to hold the detection result voltage of the conduction detecting means by a capacitor or the like.
[0012]
However, if the conduction detecting means detects the conduction of water in accordance with the timing of driving the positive pulse generating means or the negative pulse generating means by the timer means, the detection result of the conduction detecting means can be obtained even if the drive stop time is set long. The conduction of water can be detected without holding the voltage by a capacitor or the like.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of the water detecting device, FIG. 2 is a detailed circuit diagram, and FIG. 3 is a diagram showing voltage waveforms of respective parts.
[0014]
First, in FIG. 1, 1 and 2 are electrodes, 3 is a positive pulse generating means for applying a positive pulse voltage to the electrode 1, 4 is a negative pulse generating means for applying a negative pulse voltage to the electrode 1, Reference numeral 6 denotes conduction detecting means for detecting conduction between the electrode 1 and the electrode 2, reference numeral 7 denotes timer means for setting the time for driving and stopping the positive pulse generating means 3 and negative pulse generating means 4, and reference numeral 8 denotes a control unit. Subsequently, in FIG. 2 which is a specific circuit diagram, 1 and 2 are electrodes, 9 and 10 are transistors, and the transistors 9 and 10 are components of the positive pulse generating means 3. Reference numeral 11 denotes a transistor, which is a component of the negative pulse generating means 4. Reference numeral 12 denotes a capacitor provided to generate an alternating current from a direct current. 13 and 14 are transistors. A resistor 15 is connected between the emitter and the base of the transistor 13. A resistor 16 has one end connected to the base of the transistor 13 and the other end connected to the electrode 1. The transistors 13 and 14 and the resistors 15 and 16 are components of the conduction detecting means 6. Reference numeral 17 denotes a microcomputer (hereinafter abbreviated as a microcomputer) which drives and stops the transistors 9 and 11, and has both the function of the timer means 7 and the function of the control unit 8. Reference numerals 18 and 19 denote outputs of the microcomputer 17, reference numeral 20 denotes a voltage measuring terminal on the electrode 1 side of the capacitor 12, and reference numeral 21 denotes an input terminal of the microcomputer 17. A diode 22 has an anode connected to the base of the transistor 13 and a cathode connected to the emitter of the transistor 13.
[0015]
The operation of the water detection circuit thus configured will be described with reference to the voltage waveform diagram of FIG. In FIG. 3, a is a voltage waveform of the output 18 and shows a driving waveform for the positive pulse generating means 3. b is a voltage waveform of the output 19, and shows a driving waveform for the negative pulse generating means 4. Outputs 18 and 19 are output alternately every 0.5 seconds. The driving time of the positive pulse generating means 3 and the negative pulse generating means 4 is 0.05 seconds.
[0016]
First, as shown in FIG. 3A, when the H voltage is output to the output 18, the transistor 9 turns on, and then the transistor 10 turns on. The positive pole of the capacitor 12 is pulled up to the Vcc voltage (for example, 5V). Therefore, the negative pole of the capacitor 12 is also pulled up to the Vcc voltage. The negative pole of the capacitor 12 is the same as the voltage measuring terminal 20. The voltage waveform at this time is shown in FIG. When water is present between the electrode 1 and the electrode 2 when the voltage of the voltage measuring terminal 20 is high, a current flows from the voltage measuring terminal 20 to the electrode 2 via the resistors 15 and 16. When a voltage drop occurs due to the current flowing through the resistor 15 and the voltage between the base and the emitter of the transistor 13 becomes about 0.6 V, the transistor 13 is turned on. Subsequently, the transistor 14 is also turned on, and the input terminal 21 of the microcomputer 17 becomes the L voltage. FIG. 3D shows a voltage waveform of the input terminal 21. Immediately after the output terminal 18 is turned on, the state of the input terminal 21 is detected, and if the voltage is the L voltage, it can be determined that there is conduction between the electrode 1 and the electrode 2. At this timing, if the input terminal 21 is at the H voltage, it can be determined that there is no conduction. Immediately before the output terminal 18 is turned off, since the capacitor 12 has been charged, the positive pole of the capacitor 12 has risen to the Vcc voltage. The negative pole is at the GND level.
[0017]
Next, when the output terminal 19 is turned on, the transistor 11 is turned on, and the positive pole of the capacitor 12 is at the GND level. Since the capacitor 12 has been charged with the Vcc voltage, when the + pole becomes the GND level, the-pole of the capacitor 12 is lowered to the -Vcc level. Thus, a negative pulse is generated. At this time, a current flows from the electrode 2 to the electrode 1. The current flows into the negative pole of the capacitor 12 via the resistor 16 and the diode 22 to discharge the capacitor 12. When the negative pulse is being generated, the transistor 13 does not turn on, so that no conduction detection is performed.
[0018]
As described above, by alternately driving the positive pulse generating means 3 and the negative pulse generating means 4 with respect to the electrode 1, an AC voltage can be applied to the electrode 1, and there is no bias in the electrode. Does not corrode. Further, a stop period is provided between the driving of the positive pulse generating means 3 and the driving of the negative pulse generating means 4, and the intermittent driving is performed to reduce the current per unit time flowing between the electrodes 1 and 2. Can be. In this embodiment, the driving time of the positive pulse generating means 3 is 0.05 seconds, and the stop period until the next driving of the negative pulse generating means 4 is 0.45 seconds. Therefore, the current can be reduced to one tenth and the amount of water electrolysis can be reduced to one tenth as compared with the conventional example having no stop period.
[0019]
Although the timer means 7 is constituted by the microcomputer 17, it goes without saying that the timer means 7 may be constituted by discrete components.
[0020]
In the present embodiment, the driving interval between the positive pulse generating means 3 and the negative pulse generating means 4 is set to 0.5 seconds. However, the longer the interval is, the more the current flowing between the electrode 1 and the electrode 2 per unit time. And the amount of water electrolysis can be reduced.
[0021]
In addition, the electrode 2 may be also used as a tank for storing water.
[0022]
Vcc shown in the circuit diagram of FIG. 2 may be set in consideration of the maximum voltage applied to the electrode 1.
[0023]
In this embodiment, the microcomputer 17 is used to detect the detection timing of the conduction detecting means 6 at a timing synchronized with the timer means 7. However, by connecting a capacitor having a large capacitance between the collector and the emitter of the transistor 14 and increasing the resistance value of the resistor connected to the collector of the transistor 14, the time constant for charging the capacitor increases. There is no need to synchronize the detection timing. For example, assuming that the capacitance of the capacitor is 100 μF and the resistance of the resistor is 100 kΩ, the transistor 14 is turned on, the capacitor is discharged, the transistor 14 is turned off, and the capacitor starts charging. The voltage charged for one second until the transistor 14 turns on is about 0.5 V, which is within the L voltage determination range of the microcomputer. As described above, the timing of the conduction detecting means does not need to be synchronized, but by synchronizing, there is no need to provide a capacitor or the like, and the configuration can be made inexpensively. Further, by synchronizing, the drive interval between the positive pulse generating means 3 and the negative pulse generating means 4 can be set freely. For example, the interval can be set to one hour, one day, or a long time, and the electrolysis of water can be suppressed to a very small amount.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the electrode from being corroded, without depending on the potential applied to the electrode. Further, since the current flowing per unit time can be reduced, the electrolysis of water can be suppressed to a very small amount.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a water detection device according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a water detection circuit in the device. FIG. 3 is a voltage waveform diagram of a water detection circuit in the device.
1 electrode 2 electrode 3 positive pulse generating means 4 negative pulse generating means 6 conduction detecting means 7 timer means

Claims (2)

Two electrodes provided in water, positive pulse generating means for alternately applying positive and negative voltages between the two electrodes, negative pulse generating means, and detecting a current flowing between the two electrodes A water detecting device comprising: a conduction detecting means for performing the operation; and a timer means for intermittently driving the positive pulse generating means and the negative pulse generating means alternately. 2. The water detecting device according to claim 1, wherein the conduction detecting means is configured to perform the detection at a timing synchronized with the timer means.

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