JPH10178968A - Heater for water tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the water temperature of water tank from being rapidly changed far away from a target temperature. SOLUTION: This heater for water tank is provided with a heater for heating water in the water tank and a temperature detector for detecting the water temperature of water tank and when the water temperature inside the water tank detected by this temperature detector is lower than a prescribed temperature, energizing from a commercial power source to the heater is stopped. When the water temperature detected by the temperature detector is settled within the range of prescribed temperature, corresponding to the water temperature detected by the temperature detector, the heater is energized while controlling the phase of commercial power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for an aquarium, and more particularly to an aquarium heating device for heating water in an aquarium for breeding appreciation fish and small aquatic animals, or for growing aquatic plants.

[0002]

2. Description of the Related Art A conventional water tank heating device includes a heater for heating water in a water tank in which a nichrome wire is disposed in a watertight state in a cylindrical body, and a temperature detecting element including a thermistor for detecting the water temperature of the water tank. When the water temperature of the water tank detected by the temperature detection element is lower than the target temperature, the heater is energized from the commercial power supply to heat the water in the water tank, and the water temperature in the water tank detected by the temperature detection element is set to the target temperature. When the temperature is higher than the temperature, the power supply to the heater is stopped to maintain the water temperature in the water tank at the target temperature.

[0003]

However, in the conventional heating device for a water tank, when the water temperature of the water tank is lower than the target temperature, the power is continuously supplied from the commercial power supply, and when the water temperature of the water tank is higher than the target temperature. Means that the power from the commercial power supply is immediately stopped, so the water temperature of the water tank changes rapidly,
There was a problem that the water temperature became slightly different from the target temperature.

[0004] The present invention has been made in view of such problems of the conventional apparatus, and a heating apparatus for a water tank in which the water temperature of the water tank does not suddenly change to become a water temperature far from the target temperature. The purpose is to provide.

[0005]

In order to achieve the above object, a water tank heating apparatus according to the present invention includes a heater for heating water in a water tank and a temperature detecting element for detecting a water temperature of the water tank. When the water temperature in the water tank detected by the temperature detection element is equal to or lower than a predetermined temperature, the power supply from the commercial power supply to the heater is stopped, and the water temperature detected by the temperature detection element is the predetermined temperature. When the temperature is within the temperature range, the heater is energized while controlling the phase of the commercial power supply according to the water temperature detected by the temperature detecting element.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an electric circuit diagram showing an embodiment of a water tank heating device according to the present invention, wherein 1 is a commercial power supply unit, 2 is a rectified constant voltage circuit, 3 is a synchronization signal circuit, and 4 is a temperature detection circuit. Reference numeral 5 denotes a temperature control volume, 6 denotes a temperature control circuit, 7 denotes a heater drive circuit, 8 denotes a water detection circuit, 9 denotes a thermistor disconnection detection circuit, 10 denotes a heater, and 11 denotes a filter circuit.

The rectification constant voltage circuit 2 includes a transformer T ₁ , a diode bridge DS ₁ , an electrolytic capacitor C ₂ , a resistor R ₇ ,
It consists of a Zener diode ZD _3, making a DC power supply having a predetermined voltage by rectifying and converting the voltage of the commercial power supply 1.

The synchronization signal circuit 3 includes a diode D ₆ ,
D ₇ , a transistor Q ₂ , a comparator IC _1, etc., and generate a signal synchronized with the rising of the sine wave waveform of the commercial power supply 1.

[0009] Temperature sensing circuit 4 is formed of a thermistor TH, and the like resistors R _14, converts the temperature detected by the thermistor TH in voltage.

The temperature control circuit 6 comprises operational amplifiers IC _{3 to} I
C _{6 and the} like, and compares the temperature voltage from the thermistor TH with the voltage of the temperature adjustment volume 5, and outputs a signal for controlling the energization of the heater 10 in synchronization with the synchronization signal 3. Photo coupler PC ₁ transistor Q ₁ via the resistor R ₄
It is connected to, when the transistor Q ₁ is in the ON state, and the photocoupler PC ₁ in a conductive state, thereby to trigger a triac TRIAK, AC voltage is applied to the heater 10. In this temperature control circuit 6,
It compares and amplifies the temperature voltage from the thermistor TH, the resistance of which varies with the water temperature, and the voltage of the temperature adjustment volume 5, and outputs a drive signal to the transistor Q ₁ that controls energization of the heater 10. In the water tank heating apparatus according to the present invention, there are three modes for the relationship between the water temperature, the predetermined temperature, and the triac TRIAK. That is, when the water temperature is higher than the predetermined temperature (control mode A), the triac TRIAK is completely disconnected. When the water temperature is lower than the predetermined temperature (control mode B), the triac TRIAK is completely conducted. Further, when the water temperature is within the predetermined temperature range (control mode C), the triac TRIAK is turned on from the middle of the phase of the voltage waveform of the commercial power supply.

[0011] driving circuit 7 of the heater 10, the triac TRIAK, made such as optocoupler PC _1, based on a signal from the temperature control circuit 6, actually driving the heater 10.

The water detecting circuit 8 comprises a transformer T ₁ , diodes D _{2 to} D _5, etc.
A signal indicating whether energization to 0 is possible is sent to the temperature control circuit 6. In the water detection circuit 8 detects the resistance value of the inter-electrode S ₁ that are in the water. The water detection circuit 8 and the AC power is transformed by a transformer T _1, electrodes S ₁ for water detection is connected between the composed uncontrolled diode rectifier D ₂ to D _5,
Always alternating voltage is applied to the water detection electrode S _1. Electrode S
_{If one} was in water, the current flowing through the resistor with the aqueous is obtained as a DC voltage commensurate with the rectified current through the rectifier circuit D ₂ to D _5. On the other hand, the comparator I
C ₇ performs comparison between the voltage dividing resistors R _10, the specified voltage given by R ₁₁ and voltage obtained from the water sensing electrode, or between the electrodes S ₁ is located in the water, subjected to determination of whether the air ing. If water detection electrode S ₁ is in the water, for the specified voltage or more water detection voltage is inputted, it is determined that water. Also,
If it is in the air, it is determined to be in the air because a water detection voltage exceeding the specified voltage cannot be obtained. When it is determined that the triac is in the air, a blocking signal is output to the circuit for driving the triac TRIAK, which acts to prevent the triac TRIAK from conducting.

When the value of the thermistor TH reaches a certain low temperature value, the thermistor disconnection detecting circuit 9 determines that the thermistor is disconnected and gives a signal to the temperature control circuit 6 to block the power supply to the heater 10.

The heater 10 comprises a heater in which a nichrome wire or the like is sealed in a watertight state in a cylindrical body, or a ceramic heater in which a heating wire made of molybdenum or the like is embedded in a ceramic body. The heater 10 is connected to an AC power supply 10 via a heater drive circuit 7.

The filter circuit 11 includes a coil L ₁ and a capacitor C ₄ and reduces radio interference (RF ₁ ) noise generated during phase control.

Next, the operation of the control mode C will be described. Thermistor TH is via R ₁₄ rectified constant voltage circuit 2
Are connected to, this voltage is input to the preamplifier circuit of the temperature control circuit 6 consists of a comparator IC _1, resistors R ₂₀ to R ₂₂ as thermistor voltage. The purpose of this amplifier circuit is to expand a thermistor voltage change within a predetermined temperature range for performing phase control to a voltage that can be processed in a subsequent stage.

Next, is amplified upon by the amplifier circuit of the latter stage of the temperature control circuit 6 as compared with a reference voltage determined by the resistor R ₂₃ to R ₂₆ and the temperature adjustment knob 5. By comparing it with the reference voltage, the thermistor voltage amplified in the preceding stage is pseudo-variable and is shifted in parallel to the voltage range for phase control. That is, the pre-amplifier circuit of the temperature control circuit 6 simply amplifies the thermistor signal, and the post-stage performs voltage shift of the pre-stage amplified signal. As a result, the thermistor signals TH ₁ and TH ₂ shown in FIGS. 2C and 3C are obtained.

On the other hand, a comparator IC ₁ , resistors R ₃₅ and R
_43, R _44, and reference waves comprising a capacitor C ₁₀ in (sawtooth wave) generating circuit includes resistors R _35, R ₄₃ and capacitor C ₁₀
The pseudo sawtooth waves N ₁ and N ₂ synchronized with the commercial power supply voltage are created by the time constant determined by The saw-tooth wave N _1, N
Reference numeral ₂ is a reference wave for performing phase control, and raises and lowers the voltage within the range of the control voltage. This saw wave N ₁ ,
A signal for phase control is created by comparing and synthesizing N ₂ with the above-described amplified signals TH ₁ and TH ₂ .

In this control mode C, if the relationship of water temperature <center temperature within a predetermined temperature range is satisfied, and one cycle of the waveform synthesized and compared with the sawtooth wave is shown in FIG.
As shown in the waveform of the sawtooth wave N ₁ is increased, the output of the comparison synthesized by the comparator IC ₆ has a long time that by turning the transistor Q _1, off in time is shortened and the commercial as a result the power supply The heater energizing time of the half cycle becomes longer. The timing at which the transistor Q ₁ is turned on is synchronized with the power supply of the sawtooth wave N ₁ .
It is always a certain point from the rise of the commercial power supply voltage waveform.

When the relationship of water temperature> center temperature within a predetermined temperature range is satisfied, as shown in FIG.
Results of the comparison synthesis of the _2, on-time of the transistor Q ₁ is short, the off time is long operation. As described above, the transistor Q depends on the magnitude of the thermistor voltages TH ₁ and TH _2.
It is determined that the ON time of ₁ becomes longer or shorter. Note that the predetermined temperature range is about ± 0.25 ° C. with respect to the center temperature within the predetermined temperature range set by the temperature adjustment volume. This predetermined temperature range is ± 0.
When the temperature is within 5 ° C., the water temperature can be controlled so that the appreciation fish does not cause any abnormal change.

FIG. 4 is a diagram showing a power supply waveform and a phase control waveform, and FIG. 4A is a diagram showing a power supply waveform. In FIG. 4, the hatched portion is the power applied to the heater 10. FIG. 3B shows an operation waveform when water temperature = center temperature within a predetermined temperature range, and FIG. 4C shows a control waveform when water temperature <center temperature within a predetermined temperature range. ) Shows a control waveform when water temperature> center temperature within a predetermined temperature range.

Next, the overall operation method will be described. When the circuit is operated at a point where the detected temperature (water temperature) of the thermistor TH is lower than the phase control range (below a predetermined temperature), the control mode B
And the heater 10 is completely energized. Therefore, the water temperature in the water tank gradually starts to rise. When the water temperature rises and falls within a predetermined temperature range, the control mode C is set, and the heater 10 starts phase control, but the thermistor voltage still rises. In the control mode C, each time the thermistor voltage increases, the heater 10
As described above, since the heater 10 is controlled according to the voltage rise (water temperature rise) of the thermistor TH, the thermistor TH will eventually settle down at a certain temperature. Conversely, if the operation is performed at a point where the water temperature is higher than the phase control range (predetermined temperature or higher), the control mode A is set, the heater 10 is completely de-energized, and this control is maintained until the water temperature falls due to the ambient temperature. Eventually, the control mode C is set, and the heater 10 repeats the above-described energization.
Then, the thermistor TH calms down at a certain voltage (water temperature). By performing such control, the circuit can always keep the water temperature constant. That is, the heater 10 is fed back with the voltage detected by the thermistor TH, and the temperature can be controlled to be as close as possible to the target temperature.

[0023]

As described above, according to the water tank heating device of the present invention, when the water temperature detected by the temperature detecting element is within the predetermined temperature range, the water temperature detected by the temperature detecting element is reduced to the predetermined value. Power is supplied to the heater while controlling the phase of the commercial power supply accordingly, so that the heater can be accurately driven to approach the target temperature according to the water temperature of the water tank, preventing the water temperature of the water tank from changing rapidly. At the same time, the water temperature can be controlled very strictly to the target temperature.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a water tank heating device according to the present invention.

FIG. 2 is a view for explaining one mode of operation of the water tank heating device according to the present invention.

FIG. 3 is a view for explaining another mode of operation of the water tank heating device according to the present invention.

FIG. 4 is a diagram for explaining phase control of the water tank heating device according to the present invention.

[Explanation of symbols]

1: Commercial power supply, 10: heater, TH: temperature detection element

Claims (2)

[Claims] 1. A heater for heating water in a water tank, and a temperature detecting element for detecting a temperature of the water in the water tank, wherein when a temperature of the water in the water tank detected by the temperature detecting element is lower than a predetermined temperature, a commercial power supply is used. In a water tank heating device that energizes the heater and stops energizing the heater when the water temperature detected by the temperature detecting element is equal to or higher than a predetermined temperature, the water temperature detected by the temperature detecting element may be the predetermined temperature. When the temperature is within the range, the heater is energized while controlling the phase of the commercial power supply in accordance with the water temperature detected by the temperature detection element. 2. The aquarium heating apparatus according to claim 1, wherein the predetermined temperature range is within ± 0.5 ° C.