JPH0620122Y2 - Leak detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a liquid leakage detection device for detecting leakage of a non-insulating liquid such as water or a mixed liquid of water and oil.

(b) Conventional technology For example, there should be no liquid leakage under the floor of a computer room where many cables are laid, or in a storage room for articles that dislike moisture, and it is possible to detect liquid leakage early and malfunction the device. Damage to goods must be prevented in advance.

2. Description of the Related Art Conventionally, as a device for detecting liquid leakage, there has been proposed a device including a detection line whose electric characteristic changes due to adhesion of a non-insulating liquid and a detection circuit which detects a change in electric characteristic of the detection line. In addition, the applicant has already filed an application for an inexpensive and high-performance leak detection device (Act. 57-97265).
No.).

(c) Problems to be solved by the device However, as various fields of use of such a leak detection device are found, there are practical restrictions on the installation location and installation method of the device, and this It was one of the factors that hindered its spread. That is, in the conventional liquid leakage detection device, in order to detect the change in the electrical characteristics of the detection line, for example, a resistance value change is converted into a DC voltage change, and this comparator is compared with a reference voltage, and this comparator. Since the circuit that notifies the leak status based on the output was configured using individual parts, the entire device became large,
The installation location and installation method were limited.

An object of the present invention is to provide a liquid leakage detection device that can be easily downsized and can be embedded in a wall surface, for example.

(d) Means for Solving the Problems This invention is directed to a liquid leakage detection sensor whose electric resistance changes due to the presence of a non-insulating liquid, and a voltage conversion circuit for converting the electric resistance of the liquid leakage detection sensor into a DC voltage. , A comparison circuit that compares the output voltage of this voltage conversion circuit with a reference voltage, an oscillation circuit that generates a signal including an audio frequency band, and the oscillation circuit output is valid when the comparison circuit detects a liquid leakage state. A liquid leakage detection device comprising: an output control circuit for driving a sounding body according to claim 1, which integrally includes a reference voltage generation circuit, an error amplification circuit, a PWM modulation triangular wave oscillation circuit, and a PWM modulation comparator. Using an integrated circuit for switching regulator,
The error amplification circuit is applied to the comparison circuit, the PWM modulation triangular wave oscillation circuit is applied to the oscillation circuit, and the reference voltage generation circuit is used as a power supply circuit of the output control circuit. .

(e) Action FIG. 1 shows the configuration of the leak detection device of this invention. In the figure, the leak detection sensor 1 is a detection line having, for example, two electrode conductors. The voltage conversion circuit 2 converts the electric resistance change of the liquid leakage detection sensor 1 into a DC voltage change. The comparison circuit 3 compares the output voltage of the voltage conversion circuit 2 with the reference voltage Vr.
The oscillator circuit 4 generates a signal including an audible frequency band. The output control circuit 5 activates the output of the oscillation circuit 4 to drive the sounding body 6 when the liquid is leaked by the output of the comparison circuit 3. Therefore, when the electric resistance value detected by the liquid leakage detection sensor 1 is lower than a predetermined value, the sounding body 6 is driven to notify that the liquid is in a liquid leakage state. Here, the comparison circuit 3 and the oscillation circuit 4 use an error amplification circuit and a PWM modulation triangular wave oscillation circuit built in the switching regulator integrated circuit 7, and further, the integrated circuit 7 serves as a power source of the output control circuit 5. The reference voltage generating circuit in is used. By configuring the main part of the liquid leakage detection device with the switching regulator integrated circuit 7 as described above, the number of circuit components is significantly reduced, and the entire device is downsized.
Cost reduction can be achieved by using a general-purpose (non-custom) integrated circuit.

(f) Embodiment FIG. 2 shows a circuit diagram of a liquid leakage detection device which is an embodiment of the present invention. In the figure, a block 1 is a leak detection sensor, which includes a detection line SL and a terminating resistor Ro connected to the tip thereof. The block 2 is a voltage conversion circuit, which converts a resistance change of the liquid leakage detection sensor connected via the terminals P1 and P2 into a voltage change. Reference numeral 7 is a control IC for a switching regulator that performs PWM control, and here, TL494 of Texas Instruments Incorporated is used. An error amplification circuit and an oscillation circuit are built in this IC as described later. The block 5 is an output control circuit for driving the sounding body 6 composed of a piezoelectric buzzer according to the output signal of the IC 7. Further, the block 9 is a relay circuit used to turn on when the liquid is leaking and output the signal to the outside. Further, a block 8 is a power supply circuit for supplying power to the voltage conversion circuit 2 and other parts of the control circuit.

FIG. 3 shows a circuit diagram of the entire liquid leakage detection device including the circuit in the IC 7 described above, and the configuration and operation thereof will be described below.

In FIG. 3, for example, a commercial AC power supply of AC100V is connected to the primary winding N of the power transformer PT via terminals P3 and P4.
When it is supplied to No. 1, a predetermined AC voltage is generated in the one secondary winding N2 and is supplied to the terminal P2 via the resistor R5.
Zener diodes ZD1 and ZD2 stabilize the supply power supply voltage. The output of the other secondary winding N3 of the transformer PT is rectified and smoothed by the diode bridge DB and the capacitor C2, and is supplied to each unit as a 12V power source. In addition, a DC voltage of 5V is supplied to each part by the voltage-regulating circuit 10 formed in the IC 7 (see FIG. 2). The constant voltage circuit 10 is originally provided in the IC as a reference voltage generation circuit for the switching regulator circuit. However, a 5V load flip-flop FF1 and gates NOR3 and NOR which will be described later.
Since CMOS type components are used as 4, NOR5 and NOR6, the load current of 5 V is about 7 mA at the maximum, and it can be sufficiently driven. In addition, the light emitting diode LED1 is connected to the 12V power source line through the resistor R6.
Are connected. This light emitting diode is, for example, green and indicates that commercial power is supplied.

The detection line SL and the terminating resistor Ro are connected to the terminals P1 and P2, and the AC voltage of the N2 winding of the transformer is R5.
It is energized via SL, Ro and R2. The ZNR is provided to remove noise. The drop voltage of the resistor R2 is rectified and smoothed by the diode D1 and the capacitor C1 and divided by the resistors R3 and R4. Therefore, the divided output voltage at the point a is a constant voltage when there is no leakage, and if the resistance between the conductors of the detection line SL decreases due to leakage,
To rise.

Each of A1 and A2 is an error amplifier circuit provided in the IC7 (see FIG. 2), and a reference voltage circuit composed of R7, VR, R8 and C3 is connected to the + input terminal of A2 via a resistor R9. The voltage is supplied, and the output voltage of the voltage conversion circuit is supplied to the other-input terminal. As a result, A2 amplifies the difference between the reference voltage and the output voltage of the voltage conversion circuit, but here it is used as a comparator. The resistor R10 has a hysteresis characteristic. A resistor R1 is connected to the-input of the other amplifier circuit A1.
"H" potential is connected through 1, and "L" level is connected to the + input so as not to affect the output of A2,
Not used here.

Now, the oscillator circuit 4 generates a triangular wave signal determined by the time constants of R12 and C4. The output signal of the amplifier circuit A2 is supplied to the comparator CMP2 together with this triangular wave for comparison. On the other hand, the comparator CMP1 is supplied with the triangular wave signal and the reference voltage determined by the resistors R13 and R14 and the reference voltage Vd for comparison. The flip-flop FF2 is a D-type flip-flop and is triggered via the gate OR and the inverter I. The output signal of the gate OR is the output of the flip-flop FF2 and the gate NOR.
Alternately selected by 1 and NOR2 to drive transistors Q1 and Q2. Therefore, the transistor Q1 generates a rectangular wave signal PWM-controlled according to the output voltage of the amplifier circuit A2, with two cycles of the triangular wave output from the triangular wave oscillator circuit 4 as one cycle.

The two output transistors Q1 and Q2 are provided to perform the push-pull operation of the switching transistor of the switching regulator, but here, only the output of Q1 is used. Further, the comparator CMP1 and its output are provided for limiting the maximum on-duty ratio of the switching transistor to provide a so-called dead time when used as a switching regulator, but here, a predetermined reference voltage is simply input. Just not particularly used.

Since the "L" level is connected to one input of the gate NOR3 and the output of the amplifier circuit A2 is given to the other input, the output of the amplifier circuit A2 is set to the "L" level when the liquid leakage occurs. And the output of the gate NOR3 becomes "H".
It becomes a level. This causes a base current to flow through the transistor Q4 via the resistor R22, turning on Q4. Since the relay coil Rc is connected to the collector of Q4, the relay contact Re is turned on, and the state is output to the outside via the terminals P5 and P6. At the same time, the light emitting diode LED2 is energized via the resistor R23 to emit light. The light emitting diode LED2 is, for example, a red light emitting diode and indicates that the liquid is leaking. The diode D4 is provided to absorb the surge voltage when the relay coil Rc is off.

The flip-flop FF1 is a D-type positive edge trigger flip-flop with preset and clear inputs. For example, SN54H of Texas Instruments Incorporated.
C74 or SN74HC74 are used. Since the "H" level is always supplied to the preset terminal ▲ ▼ and the D terminal via the resistor R15, and the "H" level is always supplied to the clear terminal ▲ ▼ via the resistor R16, the output of the gate NOR3 is output. This flip-flop is set when the signal rises from "L" level to "H" level. The diodes D2 and D3 and the resistor R17 are OR
When the output of the FF1 is at the "L" level and the output of the amplifier circuit A2 is at the "L" level, the circuit is configured to output the "L" level to the point b.

The circuit composed of the gates NOR4 and NOR5, the resistors R18 and R19 and the capacitor C5 constitutes a rectangular wave oscillating circuit, and the output point b of the OR circuit connected to one input of the gate NOR4 becomes "L" level. When this happens, the oscillation operation starts. The gate NOR6 inverts the output signal of the transistor Q1 while the output of the oscillation circuit is at the "L" level, and the transistor NOR3 through the resistor R20.
Output to. As a result, Q3 is turned on / off by the rectangular wave signal of the audible frequency and is also modulated by the oscillation frequency of NOR4, NOR5 and the like. As a result, the voltage across the resistor R21 is applied to the sounding body 6 made of a piezoelectric buzzer and emitted.

As described above, when the liquid leakage occurs due to the change in the resistance value of the detection line SL, the relay contact Re is turned on, the LED 2 emits light, and the intermittent sound of the sounding body 6 notifies the liquid leakage. At this time, once the reset switch RSW connected to the clear terminal of the flip-flop FF1 is turned on, the ▲ ▼ terminal goes to "L" level to clear the flip-flop FF1. As a result, the potential at the point b becomes the “H” level, and the leak notification by the sounding body 6 is stopped. After that, when the liquid leakage state is resolved, the LED 2 is turned off. Further, even if the liquid leakage state is once detected and FF1 is still set, the relay contact Re is turned off when the liquid leakage state is resolved, and the liquid leakage notification by the sounding body 6 is automatically stopped. Regardless of the state of FF1, if the liquid leaks again after that, the relay contact Re is turned on, the LED 2 is turned on, and the sounding body 6 is emitted.
As described above, since the reset switch RSW of the flip-flop FF1 does not forcibly prohibit the drive signal for the sounding body 6, for example, the restoration operation for canceling the inhibition state becomes unnecessary and the restoration operation may be forgotten. Absent.

By turning on the test switch TSW provided in the voltage conversion circuit 2 (see FIG. 2), it is possible to test whether the entire circuit other than the leak detection sensor 1 operates normally. When the test switch TSW is turned on, the resistor R1 is connected between the terminals P1 and P2. The resistance value of R1 is, for example, 1 KΩ, which is a pseudo leak model. Therefore, if the circuit is normal, TSW
When the power is turned on, the potential at the output point a of the voltage conversion circuit rises and becomes equivalent to a liquid leakage state, and the relay contact Re turns on and the LED
The lighting of 2 and the notification by the sounding body 6 are performed.

As described above, according to the embodiment of the present invention, the error amplification circuit in the switching regulator control IC is
It is used as a comparison circuit that compares the reference voltage with the output voltage of the voltage conversion circuit, and a triangular wave oscillation circuit for PWM control and a comparator that constitutes the PWM control circuit are used as an oscillation circuit that generates a signal including an audio frequency band. Furthermore, the constant voltage circuit that generates the reference voltage is used as the stabilized power supply circuit of the output control circuit, so that the number of parts is significantly reduced. Further, since the piezoelectric buzzer is used as the sounding body, its mounting space is hardly restricted. In addition, the gate NO which constitutes a part of the output control circuit 5
A single packaged IC can be used for R3, NOR4, NOR5, and NOR6, and the number of components forming the output control circuit does not increase.

In the embodiment, the circuit for interrupting the rectangular wave signal output from the switching regulator control IC is provided, but when the output voltage of the voltage conversion circuit is equal to or lower than a predetermined value, the output of the comparator CMP2 in the IC is output. If the reference voltage of the amplifier circuit A2 is set so that the on-duty ratio of the signal becomes 0%, the rectangular wave signal can be generated from the transistor Q1 only in the liquid leakage state. In this case, the circuit from the comparator CMP2 to the transistor Q1 can be used as the output control circuit according to the present invention, and the output control circuit 5 shown in FIG. 2 can be omitted.

(g) Effects of the Invention As described above, according to this invention, the number of parts that configure the circuit is significantly reduced, and the leak sound is output by the alarm sound output by the sounding body. It can be miniaturized and can be installed by being embedded in a wall surface, for example. Furthermore, by reducing the number of parts using a general-purpose integrated circuit, it has become possible to significantly reduce costs. As a result, the leak detection device can be applied to various fields that were not possible in the past.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of this invention. Second
FIG. 3 and FIG. 3 are circuit diagrams of a liquid leakage detection device according to an embodiment of the present invention, and particularly FIG. 3 is an overall circuit diagram including the circuit in the semiconductor integrated circuit 7 shown in FIG. is there.

Claims (1)

[Scope of utility model registration request] 1. A leak detection sensor whose electric resistance changes due to the presence of a non-insulating liquid, a voltage conversion circuit for converting the electric resistance of this leak detection sensor into a DC voltage, and an output voltage of this voltage conversion circuit. A comparison circuit for comparing with a reference voltage, an oscillation circuit for generating a signal including an audio frequency band, and an output control for driving the sounding body by enabling the oscillation circuit output when the comparison circuit detects a liquid leakage state. And a circuit, which uses a reference voltage generation circuit, an error amplification circuit, a PWM modulation triangular wave oscillation circuit, and a switching modulation integrated circuit that integrally includes a PWM modulation comparator,
The error amplification circuit is applied to the comparison circuit, the PWM modulation triangular wave oscillation circuit is applied to the oscillation circuit, and the reference voltage generation circuit is used as a power supply circuit of the output control circuit. Leak detection device.