JPS5854401B2 - Temperature conversion setting circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a temperature conversion setting circuit equipped with a temperature-sensitive resistance element that converts temperature changes such as water temperature into changes in resistance value. An object of the present invention is to provide an inexpensive temperature conversion setting circuit that does not cause overshoot in an automatic temperature controller.

Conventionally, a temperature conversion setting circuit 5 has been proposed in which a DC power supply 1, a resistor 2, a variable resistor 3, and a temperature-sensitive resistance element 4 are connected in series as shown in FIG. If you try to apply it, the following problems will arise.

In other words, when this circuit 5 is applied to a gas water heater, the variable resistor 3 is used to set the water temperature, and the temperature-sensitive resistance element 4 is used to detect the water temperature, and the difference between the two is determined by the output terminal. 6
It is expressed as a voltage value.

Then, this voltage value is proportionally differentiated, and the combustion amount of the burner is controlled by this proportionally differentiated value, thereby attempting to maintain the water temperature at a set temperature.

However, such a device that differentiates the voltage appearing at the output terminal 6 causes a large overshoot when the set temperature is varied.

To put this into concrete terms, when variable resistor 3 is operated to change the water temperature from 40°C to 60°C, the voltage at output terminal 6 changes instantaneously, and its differential value becomes extremely large. As a result, the temperature of the hot water far exceeds 60°C and reaches 80°C.

However, users who do not know about such overshoot may use this hot water believing that it is 60°C, which may result in burns.

Therefore, the present invention attempts to eliminate the above-mentioned conventional drawbacks by using a simple configuration in which a capacitor is connected in parallel to a variable resistor, and also attempts to improve the response speed of an automatic temperature control system.

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, 7 is a temperature conversion setting circuit, and this circuit 7
A DC power supply 8, a resistor 9, a variable resistor 10, and a temperature sensitive resistance element 11 as a temperature detecting element such as a thermistor are connected in series, and a capacitor 12 is connected in parallel to the variable resistor 10.

In other words, the temperature conversion setting circuit 7 of the present invention has a capacitor 12 connected in parallel to the conventional temperature conversion setting circuit 5, but by installing this capacitor 12, the following voltage is applied to the output terminal 13. began to appear.

First, a case will be described in which the resistance value of the variable resistor 10 is varied stepwise from R1 to R2 (R1<R2) for temperature setting.

In this case, the voltage appearing across the capacitor 12 gradually increases from the voltage (1) of the following equation (1,) to the voltage (2) of the equation (n) with an appropriate time constant.

As a result, the voltage appearing at the output terminal 13 is naturally the following (I
The voltage gradually increases from the voltage ■3 in the formula II) to the voltage ■4 in the formula (IV) with a first-order lag.

However, R3, R4, and E of formula (nl) and formula 0 are the above (L)
Formula (II) is applied mutatis mutandis.

Next, the resistance value of the temperature-sensitive resistance element 11 is changed from R11 to R4□(
The following describes the case where R+x <R42) changes in a stepwise manner.

In this case, when the resistance value of the temperature-sensitive resistance element 11 is R4□, the voltage ■ appearing across the capacitor 12 becomes as follows (V)2.

However, V) Formula (7) R,, R3, Ec above (1) 2~(
■) Apply the formula mutatis mutandis.

After that, the resistance f of the temperature-sensitive resistance element 11 changes from R4□ to R4
When the voltage changes to □, the voltage 6 appearing across the temperature sensitive resistance element 11 rises as shown in the following equation (9), but at this time the voltage 2 across the capacitor 12 does not drop instantaneously.

However, R1, R3, and E of the Vl1 formula correspond to the above (1) 2 to (I
V) Apply the formula mutatis mutandis.

Therefore, the resistance value of the temperature-sensitive resistance element 11 changes from R21 to R4.
At the moment when the voltage changes to □, the voltage V7 at the output terminal 13 rises as shown in the following Ura equation.

However, for R1, R3, and E of the VID formula, the above formulas (1 to 2) apply mutatis mutandis.

After that, the capacitor 12 discharges over time,
As a result, when the voltage 5 becomes as shown in the following equation (nx), the voltage v7 appearing at the output terminal 13 drops to the following equation (IX) as this voltage drops.

However, for R3 and E of the aX) formula and the (ω formula), the above (I) Ni~Jun formula is applied mutatis mutandis.

In other words, the resistance value of the temperature-sensitive resistance element 11 is R4□
When there is a step change from R42 to R42, the output terminal 13
The voltage (■7) appearing in was changed differentially.

From the above description, it is clear that the temperature conversion setting circuit 7 of the present invention has a first-order delayed waveform voltage at the output terminal 13 when the resistance value of the variable resistor 10 is changed by simply adding the capacitor 12, and also a temperature-sensitive resistor. When the resistance value of the element 11 changed, a differential waveform voltage could be obtained at the output terminal 13.

Therefore, when this temperature conversion setting circuit 7 is used in a gas water heater, for example, it is sufficient to amplify the above-mentioned differential waveform and control the combustion amount of the burner using this amplified value. will not cause it.

In other words, in the case of the conventional temperature conversion setting circuit 5, the variable resistor 3
When the set temperature was varied, a large differential value appeared, resulting in overshoot.

However, in the temperature conversion setting circuit 7 of the present invention, the variable resistor 1
When the set temperature is varied by 0, a first-order delayed waveform voltage appears, so this does not cause overshoot.

Moreover, when the temperature-sensitive resistance element 11 detects the water temperature and changes its resistance value, a voltage with a differential waveform appears, so the water temperature can be appropriately and accurately detected by the voltage of this differential waveform. The water temperature will be maintained at the set temperature set by the resistance value of the variable resistor.

FIG. 2 shows a second embodiment of the present invention, in which a resistor 14 is connected in parallel to the temperature-sensitive resistance element 11 in order to provide the temperature-sensitive resistance element 11 with linearity.

Further, FIG. 3 shows a third embodiment of the present invention, in which resistors 15 and 16 are added to constitute a bridge circuit,
The output was taken out from output terminals 13, 13'.

In addition, in each of the above embodiments, an example was explained in which the variable resistor 10 was used alone, but as shown in FIGS. 4 and 5, the resistor 17 may be connected in series or in parallel with the variable resistor 10. It's okay.

As described above, according to the present invention, by simply connecting only one capacitor in parallel to a variable resistor, a change in the resistance value of the variable resistor can be responded to by a first-order lag voltage from its output terminal, or a change in the resistance value of the temperature-sensitive resistor element. A differential voltage can be obtained from its output terminal.

Therefore, when this is applied to a water heater, it is possible to obtain hot water at the set temperature without causing an overshoot when changing the resistance value of the variable resistor, that is, when changing the set temperature, as in the case of conventional methods. If the water temperature suddenly changes, the differential value is output, allowing quick correction and faster response.

Therefore, it is very easy for the user to use, and moreover, there is no risk of burns caused by hot water due to overshoot.

Furthermore, since the configuration of the present invention requires only one additional capacitor as described above, it can be provided at a low cost, and since the configuration is simple, malfunctions and failures are extremely reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a temperature conversion setting circuit according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a temperature conversion setting circuit according to a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a temperature conversion setting circuit according to a second embodiment of the present invention. 4 is a circuit diagram of a temperature conversion setting circuit according to a third embodiment of the present invention, FIG. 4 is a circuit diagram of a main part of a temperature conversion setting circuit according to a fourth embodiment of the present invention, and FIG. A main part circuit diagram of the temperature conversion setting circuit according to the embodiment, and FIG. 6 is a circuit diagram of a conventional temperature conversion setting circuit. 8...DC power supply, 9...Resistor, 10.
...Variable resistance, 11...Temperature-sensitive resistance dice,
12... Capacitor.

Claims (1)

[Claims] 1. A temperature conversion setting circuit in which a DC power supply, a variable resistor, and a temperature-sensitive resistance element, which is a temperature detector of an automatic temperature controller, are connected in series, and a capacitor is connected in parallel to the variable resistor.