JPH0520761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control device that prevents errors in displayed temperature from being biased toward the plus side or minus side when temperature is displayed digitally.

Conventional configuration and its problems A conventional temperature control device will be explained below.

FIG. 1 shows an example of a conventional temperature control device. Reference numeral 1 denotes a thermistor with negative characteristics, which is heat-sensitively attached to the temperature-controlled body. 2 is a DC power supply.
One end of the thermistor 1 is connected to the positive electrode of a DC power supply 2. 3 to 6 are resistors, one end is thermistor 1
Commonly connected to the other end. 7 to 10 are transistors whose collectors are connected to the other ends of the resistors 3 to 6, respectively. 11-14 are resistors, one end of which is connected to the bases of transistors 7-10, respectively, and the other end connected to output ports 15a-15d of microcomputer 15. 16 is a comparator, the output terminal of which is connected to the input port 15e of the microcomputer 15. 17 is a resistor, one end of which is connected to the positive electrode of the DC power supply 2.
18 is a resistor, one end of which is connected to the negative electrode of the DC power supply 2. A common connection end of the resistors 17 and 18 is connected to the positive input of the comparator 16. Thermistor 1
The common connection ends of the resistors 3 to 6 are connected to the negative input of the comparator 16. Numerals 19 to 22 are light emitting diodes whose anodes are commonly connected and connected to one end of a resistor 23. The other end of the resistor 23 is connected to the positive electrode of the DC power supply 2. Light emitting diode 19~
22 cathodes are connected to output ports 15f to 15i of the microcomputer 15, respectively. 24 is a resistor, one end of which is connected to the positive electrode of the DC power supply 2. 25 is a switch, one end of which is connected to the negative electrode of the DC power source 2. A common connection end of the resistor 24 and the switch 25 is connected to the input port 15j of the microcomputer 15. 26
is a heater driving means, and the microcomputer 15
energization to the heater 27 is controlled by a signal from the output port 15k.

Next, the operation of the conventional temperature control device configured as described above will be explained. FIG. 2 shows the main part of a flowchart of control by the microcomputer 15. The one shown in Figures 1 and 2 has four temperatures to choose from, and the switch 2
Every time you press 5, for example, 100℃→120℃→140℃→
Setting temperature interval Δt = 20°C, such as 160° → 100°C
The set temperature can be changed. Light emitting diode 19~ to display the setting
22 corresponds to the four temperatures mentioned above, for example
When 120℃ is set, light emitting diode 20
lights up continuously. Resistors 17 and 18 provide a constant reference voltage to comparator 16. Comparator 16 compares the reference voltage determined by resistors 17 and 18 with the voltage determined by thermistor 1 and resistors 3 to 6, and provides the result to microcomputer 15. Resistance 17,
The resistance values of the thermistor 1 and resistors 3 to 6 are _{R t and} R ₁ respectively.
˜R ₄ , the output of the comparator 16 is: When transistor 7 is turned on, (the voltage of DC power supply 2 is E(v)) R ₁ /R _t +R ₁・ER _r /2R When _r・E, low level R ₁ /R _t +R ₁・ER When _r /2R _r.E , it is a high level, that is, when R _t R ₁ , it is a low level. When R _t R ₁ , it is a high level. Similarly, if transistors 7 to 10 are respectively T _r1 to T _r4 , when T _ri is on (i is 1, 2, 3, 4), R _t R _i is low level, R _t R _i is high level. Become.

For example, when the temperature is 100℃, 120℃, 140℃, and 160℃, the resistance value of thermistor 1 is R _t100 ,
If R _t120 , R _t140 , R _t160 , then R ₁ = R _t100 , R ₂ = R _t120 R ₃ = R _t140 , R ₄ = R _t160 (R ₁ > R ₂ > R ₃ > R ₄ ) , the microcomputer 15 can determine whether the temperature of the thermistor 1 is higher or lower than the above-mentioned four temperatures.

In FIG. 2, it is determined in step 28 whether the switch has been pressed, and if the switch has been pressed, the set temperature is shifted by one. In other words, when the switch is pressed when the temperature is set to 100°C, the microcomputer 15 stores in the memory section of the microcomputer 15 that the setting has become 120°C.

In step 30, the corresponding light emitting diode is turned on based on the set temperature data stored in the storage section. LED ₁ to _{LED 4} for light emitting diodes 19 to 22 respectively
If the setting is 120℃, the microcomputer 15 will set the output port 15g to low level.
Set f, 15h and 15i to high level and LED ₂
lights up. In step 31, the microcomputer 15 sets the corresponding output ports 15a to 15d to a high level based on the set temperature data stored in the storage section. In other words, when the temperature is set at 120° C., the output port 15b is at a high level, and the output ports 15a, 15c, and 15d are at a low level, and the transistor 8 is turned on. As a result, the output of the comparator 16 becomes the thermistor 1
If the temperature is higher than 120℃, low level, 120℃
The level will be lower than that of the high level. The microcomputer 15 stores the output of the comparator 16 at this time in the storage section as temperature control data. In steps 32 and 33, if the temperature control data obtained in step 31, which is the output of the comparator 16, is at a high level, the heater is turned on, and if it is at a low level, the heater is turned off. After step 34, the current temperature detection means is operated to detect in which range of temperatures determined by the resistors 3 to 6 the temperature of the thermistor 1 is.

If the temperature of thermistor 1 is lower than the temperature determined by resistor R _i and higher than the temperature determined by resistor R _i-1, the current temperature is displayed by blinking LED _i-1 , and the temperature of thermistor 1 is Steps 35-38 show that when the temperature of the thermistor 1 is lower than the temperature determined by the resistor _R1 , the LED ₄ blinks when the temperature is higher than the temperature determined by the resistor _R4 , and none of the light emitting diodes blinks when the temperature of the thermistor 1 is lower than the temperature determined by the resistor R1. . Further, when the light emitting diode indicating the set temperature matches the light emitting diode indicating the current temperature, the light emitting diode becomes blinking.

FIG. 3 shows the thermistor temperature and the lighting and blinking states of the light emitting diode. (However, when the setting is set to 160°C) The above is the operation of the conventional temperature control circuit, but such a configuration has the following drawbacks.

In Figure 3, LED ₄ has a temperature setting of 160℃.
In contrast, the current temperature display starts blinking when the thermistor temperature exceeds 160°C. The same goes for the other light emitting diodes; LED ₃ indicates 140°C when displaying the set temperature, but blinks when the thermistor temperature is between 140°C and 160°C when displaying the current temperature. LED ₂ and LED ₁ also have a temperature difference of 0°C to +20°C between when the set temperature is displayed and when the current temperature is displayed. If the set temperature interval is Δt°C, the range of error ε in the current temperature display is 0εΔt.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
The temperature is controlled to maintain the set temperature, the set temperature and the current temperature are displayed using the same display means, and the temperature range is the same above and below the corresponding temperature of each display element. It is an object of the present invention to provide a temperature control device capable of displaying a current temperature without deviation.

Structure of the Invention The present invention is capable of extracting a voltage at a connection point between a thermistor and a resistor in a series circuit consisting of a thermistor and a resistor connected to both ends of a voltage source, and a voltage extracted from the midpoint of the series circuit of resistors connected to both ends of the voltage source. The temperature of the thermistor is detected by comparing it with the reference voltage set, and the energization to the heater is controlled based on the result, and the set temperature can be selected in N stages by switching the resistor connected in series with the thermistor. a temperature control means, a current temperature detection means for detecting a temperature different from a set temperature by changing a reference voltage by connecting a new resistor in parallel with one of the resistors forming a series circuit for generating a reference voltage; This temperature control device is equipped with display means for displaying a set temperature and a current temperature in N stages using display elements.

DESCRIPTION OF EMBODIMENTS FIG. 4 shows a block diagram of a temperature control device which is an embodiment of the present invention. 39 is a temperature control means that can select the set temperature in N stages (T ₁ , T ₂ ...T _N ℃, N is a natural number), which includes a thermistor 1, resistors 3 to 6, transistors 7 to 10, comparator 16, and a resistor. 17, 18, switch 25, heater drive means 2
6, a heater 27, etc. 40 is the current temperature
T ₁ ′, T ₂ ′……T _N ′℃ (T ₁ ′＜T ₁ ＜T ₂ ′＜T ₂ ……＜
This is a current temperature detection means for detecting the temperature of T _N ′<T _N ). Reference numeral 41 denotes a display device for displaying the set temperature and the current temperature, and is composed of light emitting diodes 19 to 22. FIG. 5 is a circuit diagram of a temperature control device which is an embodiment of the present invention. The same parts as in FIG. 1 are given the same reference numerals. In addition to FIG. 1, one end of a resistor 42 is connected to the positive input of the comparator 16, and the other end is connected to a transistor 43.
connected to the collector. transistor 43
The base of is connected to the output port 15l of the microcomputer 15 via a resistor 44. The resistor 42 and transistor 43 together with the thermistor 1, resistors 3 to 6, transistors 7 to 10, comparator 16, resistors 17 and 18, etc. constitute current temperature detection means 40.

Next, the operation of this embodiment will be explained.

Temperature setting, set temperature display, and temperature control operate exactly the same as in Figure 1.

When the current temperature detection means 40 operates, the output port 15l of the microcomputer 15 is set to a high level and the transistor 43 is turned on. When the transistor 43 is turned on, the resistor 42 is connected in parallel to the resistor 18, and the reference potential V ₊ of the positive input of the comparator 16 decreases.

As in the case of the conventional example, the resistance values of resistors 3 to 6 are set to R ₁ , R ₂ , R ₃ , and R ₄ respectively, and the set temperature is set to 100.
℃, 120℃, 140℃, 160℃, the resistance value of thermistor 1 at this time is R _t100 , R _t120 , R _t140 , R _t160 resistance 4
Assuming that the resistance value of 2 is R _c and the resistances 17 and 18 are R _r , the thermistor resistance value R _t of the detected temperature when transistor 43 and transistor 7 are turned on is R ₁ /R _t +R ₁・E=R _r R _c ／R _r ＋R _c ／R _r R _c ／R _r ＋R _c ＋R _r・
E ∴R _t =R _c +R _r /R _c・R ₁ , and as the transistor 43 turns on,
R _t becomes R _c +R _r /R _c times. Since the thermistor 1 has a negative characteristic, the detected temperature can be lowered by turning on the transistor 43.

In other words, since the transistor 43 is off during temperature control, the detected temperatures are 100℃, 120℃, 140℃,
160° C., but since the transistor 43 is turned on when the current temperature is detected, a temperature lower than the above-mentioned temperatures is detected. By appropriately selecting R _c here, the detected temperatures at the time of current temperature detection can be brought closer to 90°C, 110°C, 130°C, and 150°C, respectively. Figure 6 shows the thermistor temperature and the lighting and blinking states of the light emitting diode (when the setting is 160°C).

Effects of the Invention As is clear from the above embodiments, the temperature control device of the present invention performs temperature control to maintain a set temperature, and displays the set temperature and current temperature using the same display means. Furthermore, it is possible to display the current temperature without deviation by having the same temperature range above and below the corresponding temperature of each display element, making it more practical than conventional temperature control devices.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional temperature control device, Fig. 2 is a flowchart of a conventional temperature control device, Fig. 3 is a timing chart showing a conventional current temperature display, and Fig. 4 is an embodiment of the present invention. FIG. 5 is a circuit diagram of the temperature control device, and FIG. 6 is a timing chart showing the current temperature display by the temperature control device. 1...Thermistor, 3-6...Resistor, 15...
Microcomputer, 16...Comparator, 19~
22... Light emitting diode, 25... Switch, 3
9...Temperature control means, 40...Current temperature detection means, 41...Display device.

Claims (1)

[Claims] 1. The potential at the connection point between the thermistor and the resistor in a series circuit consisting of a thermistor and a resistor connected to both ends of the voltage source, and the reference voltage taken from the midpoint of the series circuit of the resistor connected to both ends of the voltage source. The current to the heater is controlled based on the result of detecting the temperature of the thermistor, and the set temperature is set in N stages (T ₁ , T ₂ ,... ...,
temperature control means that can be selected from T _N (℃N is a natural number);
By connecting a new resistor in parallel to one of the resistors forming the series circuit for generating the reference voltage, the reference voltage is changed, and a temperature T ₁ ', which is different from the set temperature, is obtained.
T ₂ ′,...T _N ′ (T ₁ ′＜T ₁ ＜T ₂ ′＜T ₂ ＜...＜T _N ′
1. A temperature control device comprising: a current temperature detection means for detecting <T _N ); and a display means for displaying the set temperature and the current temperature in N stages using N display elements.