JP3215037B2 - Water tank heating device - Google Patents

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 this conventional water tank heating device, 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. However, since the power supply from the commercial power supply is immediately stopped, there is a problem that the water temperature of the water tank changes rapidly and the water temperature becomes 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 detecting element is lower than a predetermined temperature, power is supplied to the heater, and when the water temperature detected by the temperature detecting element is higher than the predetermined temperature, power supply to the heater is stopped. When the water temperature detected by the temperature detecting element is within the predetermined temperature range, the heater is intermittently energized in accordance with 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 apparatus according to the present invention, wherein 1 is an AC power supply composed of a commercial power supply, 2 is a heater, 3 is a rectifier circuit, and 4 is a thermistor. A temperature detection element, 5 is a water detection circuit, 6 is a control circuit, and 7 is a heater drive circuit.

The heater 2 includes a heater in which a nichrome wire or the like is sealed in a watertight state in a cylindrical body, a ceramic heater in which a heating wire made of molybdenum or the like is embedded in a ceramic body, or the like. The heater 2 is connected to an AC power supply 1 via a heater drive circuit 7.

The rectifier circuit 3 includes a diode D ₁ , a capacitor C ₁ , a resistor R ₁ , a Zener diode ZD ₁ , a transformer T
_The DC power supply is made by rectifying the AC power supply 1.
The LED ₁ in the rectifier circuit 3 is a light emitting diode that indicates the state when AC power is supplied.

[0009] Temperature sensing element 4, the resistance through the R ₈ are connected to the rectifier circuit 3, a comparator IC resistor R ₈ and the temperature sensing element 4 controls the voltage determined by the voltage dividing resistors between themselves circuit 6 Enter ₃

The water detecting circuit 5 comprises a water detecting electrode S ₁ , a transformer T ₁ , bridge type diodes D _{2 to} D ₅ , a comparator IC _{1 and the} like, and determines whether or not water exists between the water detecting electrodes S _1. Detect. The water detection circuit 5 is constituted by providing a water detection electrodes S ₁ between the composed rectifier circuit in the AC power supply 1 and the diode D ₂ to D _5, which is transformed by the transformer T _1, water detection electrode the S _1, suffering constantly alternating voltage. If water sensing electrode S ₁ is there in the water, the current flowing through the resistor with the the water is rectified through the diode D ₂ to D _5, obtained as a DC voltage commensurate with the rectification value.

On the other hand, the comparator IC ₁ has a voltage dividing resistor R
₂ , the reference voltage provided by R ₃ and the water sensing electrode S ₁
Comparing the resulting voltage (water detection voltage) from either water detection electrode S ₁ is located in the water, is, whether or determination is in the air. If water detection electrode S ₁ is in the water, since the reference voltage or more water detection voltage is input to the comparator IC _1, it can be identified as water. In addition, when it is in the air, it is determined to be in the air because a water detection voltage exceeding the reference voltage cannot be obtained. When a water detection voltage higher than the reference voltage is obtained, the comparator IC
Output from the _1, will be able to energize the heater 2 by keeping the base potential Tran Njisuta Q ₁ to a predetermined potential. When a water detection voltage higher than the reference voltage cannot be obtained, there is no output from the comparator IC ₁ and the transistor Q ₁
Is not lowered and the heater 2 is not energized.

The control circuit 6 includes operational amplifiers IC _{2 to} IC ₆
And it consists, such as a transistor Q _1, the temperature sensing element 4
The heater drive circuit 7 is operated based on the water temperature of the water tank detected in step (1).

The heater drive circuit 7 includes a photocoupler P
C _1, consists like triac TR _1, drives the heater 7 based on the signal generated by the control circuit 6. In addition,
The LED ₂ in the heater drive circuit 7 is a light emitting diode for displaying the state when the heater 2 is energized. LED that indicates the status of connection to AC power supply 1
LED indicating that the heater 2 is energized separately from ₁
By providing ₂ , it is possible to separately display whether or not the AC power supply 1 is connected to the AC power supply 1 and whether or not the heater 2 is energized. You can recognize that state.

Next, the operation of the heating device configured as described above will be described. First, the thermistor voltage by dividing the output of the rectifier circuit 3 in the resistance R ₈ and the temperature sensing element 4, and inputs the thermistor voltage to the positive terminal of the operational amplifier IC _3. The reference voltage is formed by the comparator IC ₂ and the comparator I
Amplifying the thermistor voltage at C _3. In this case, the comparator IC _2, the amplification factor is determined by the resistor R ₁₂ to R _14. This is to make it easier to compare with the reference voltage.

Next, in the operational amplifier IC ₄ , the resistor R ₁₅ ,
The reference voltage determined by R ₁₆ , R ₁₉ , R ₂₀ and the variable resistor VR ₁ is added and then amplified. This is because, by adding the reference voltage, the thermistor voltage is fluctuated in a pseudo manner, and is moved in parallel to a voltage range for duty control.

On the other hand, an operational amplifier IC ₅ , a resistor R ₂₃ ,
A triangular wave is generated by R ₂₄ and R ₂₇ and the capacitor C ₆ . The time constant of this triangular wave is determined by the resistors R ₂₇ and R ₃₀ and the capacitor C ₆ . This triangular wave serves as a reference voltage for performing duty control, as shown in FIG. It is possible to perform a duty control by comparing synthesizing a thermistor voltage T _V is moved in parallel to amplify the reference triangular wave and as described above.

[0017] Suppose, as shown in the left side of FIG. 2 (a), when the thermistor voltage T _V is a was in a low voltage point of the reference triangular wave, comparing synthesized thermistor voltage T _V and the reference triangular wave, the reference triangular wave 1 when viewed in the cycle, long the voltage of the triangular wave side is high time, there is a short low time thermistor voltage T _V. Therefore, as shown in FIG. 2 (b), the output of the comparison synthesized by the operational amplifier IC ₆ has a long time that by turning the transistor Q _1, the time is off becomes shorter. On the other hand, as shown in the right side of FIG. 2 (a), when the thermistor voltage T _V is increased, as shown in the right side of FIG. 2 (b), the ON time of the transistor Q ₁ is short, the off time is long operation. Or longer on-time of the transistor Q ₁ thus by the size of the thermistor voltage T _V, or shorten.

As shown in FIG. 1, the transistor Q ₁ is connected to the photocoupler PC ₁ of the heater drive circuit 7 via a resistor R _31.
Is connected to the transistor Q ₁ is when you are turned on the photo-coupler PC ₁ in a conductive state, whereby the AC voltage 1 to the heater 2 to trigger a triac TR ₁ is applied. As a result, fed back to the heater 2 by the thermistor voltage to a control so that the temperature near as possible to the target temperature set by the variable resistor VR _1. Target temperature set by the variable resistor VR ₁ is made at slightly lower than the highest point of the reference triangular wave.

[0019] Incidentally, when the thermistor voltage T _V is a period of time less than the lowest point O _L of the reference triangular wave, an operational amplifier IC
The output of ₆ turns on, the transistor Q ₁ is are energized in succession to the heater 2 is turned on all the time. Further, when the thermistor voltage T _V is higher predetermined period than the highest point O _H of reference triangular wave, the output of the operational amplifier IC ₆ is turned off, the transistor Q ₁ is power supply to the heater 2 is turned off all the time is stopped completely . Therefore, in the water tank heating device according to the present invention, the temperature detected by the temperature detection element 4
The drive is performed in three modes: a mode in which the heater 2 is continuously energized, a mode in which the heater 2 is not energized at all, and a mode in which the heater 2 is energized intermittently. That is, when lower than the predetermined temperature is a lowest point O _L of the thermistor voltage reference triangular wave is energized continuously to the heater 2,
Is lower than the predetermined temperature is the highest point O _H of the reference triangular wave is not at all energized to the heater 2, the lowest point of the reference triangular wave O _L
And when the range of the predetermined temperature is between the highest point O _H, it is intermittently operated in accordance with the thermistor voltage T _V.

As shown in FIG. 1, the temperature sensing element 4 moiety used was put into water Connecting temperature sensing element 4 to the AC power supply 1 via the transformer T ₁ is higher even deteriorated insulating resin There is no danger of electric shock due to voltage and it is safe.

[0021]

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. Since the heater is intermittently energized accordingly, the heater can be accurately driven so as to approach the target temperature in accordance with the water temperature of the water tank, and it is possible to prevent the water temperature of the water tank from changing rapidly, and Can be controlled very strictly to reach 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 diagram showing a relationship between a set temperature, a detected temperature, and a heater driving time of the water tank heating device according to the present invention.

[Explanation of symbols]

1 AC power supply 2 heater 3 rectifier circuit 4 temperature detection element 6 control circuit 7
・ Heater drive circuit

Claims (2)

(57) [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. When the water temperature in the water tank detected by the temperature detecting element is lower than a predetermined temperature, the heater is connected to the heater. In a water tank heating device that energizes 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 is in a range of the predetermined temperature. When the temperature is within the range, the heater is intermittently energized in accordance with the water temperature detected by the temperature detection element. 2. The heating device for a water tank according to claim 1, wherein the temperature detecting element is connected to an AC power supply for supplying electricity to the heater via a transformer.