JPH0342781B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a temperature detection device for measuring temperatures at multiple locations using multiple thermistors.

Conventional technology When measuring temperature with a thermistor, the resistance value of the thermistor, that is, the temperature, is usually measured by connecting a resistor in series with the thermistor, applying a constant voltage, and detecting the voltage generated across the resistor or the thermistor. Detected.

FIG. 4 shows a conventional example in which temperatures are detected at a plurality of locations, for example, three locations. 1-3 are thermistors, 4-
Reference numeral 6 represents a resistor, and reference numerals 7 to 9 represent voltage comparators, three of which correspond to the three temperature measurement points.
10 is a microcomputer, 11 is a D/A converter, 12-1
4 is an LED display unit 5 connected in a matrix.
2 and the key input section 53, and is a means often used as a man-machine interface in circuits using such microcomputers. 15 is a power supply, and 16-18 are pull-up resistors of voltage comparators 7-9, respectively. In addition, each voltage comparator 7
-9 are each independently used for temperature detection at three locations. That is, the binary data output from the microcomputer 10 by the D/A converter 11 becomes an analog voltage, which is applied to the inverting input terminal of each voltage comparator 7 to 9, and the voltage generated in each of the resistors 4 to 6. Temperature detection is performed by independently comparing and testing. In the figure, 19-27 are resistances, 28-
39 is an LED constituting the LED display section 52; 40 to 39;
45 and 46 to 51 are key input sections 53, respectively.
diodes and switches constituting, 54-7
3 indicates an input terminal of the microcomputer 10.

Problems to be Solved by the Invention In such conventional temperature detection circuits, although they have the same purpose of temperature detection, they each use independent voltage comparators, which is extremely uneconomical in terms of the number of components. Moreover, it cannot be said that the limited input terminals of the microcontroller are effectively utilized.

The present invention solves these problems and aims to economically perform multiple temperature detections.

Means for Solving the Problems The present invention solves these problems by providing a thermistor or a temperature measuring block in combination with one or more resistors that compensate for the linearity of the temperature-resistance characteristic of the thermistor. , one terminal of the thermistor or the temperature measurement block is all connected to the same resistance and one input terminal of the same voltage comparator, and the other terminal of the thermistor or the temperature measurement block is Each thermistor or temperature measuring block is connected directly or via a diode to a switching element for dynamically driving the LED display or key input unit connected in a matrix, and each thermistor or temperature measuring block has a switching element synchronized with the dynamic driving. This is a configuration in which voltage is applied in a time-division manner.

Function As described above, the present invention applies a voltage to the thermistor in a time-division manner using dynamic drive signals for LED display and key input, and compares the voltages generated in the voltage dividing resistors that change every moment with a single voltage comparison. Since comparison and verification are performed in a time-sharing manner using different devices, the number of components and the number of input terminals of the microcomputer that processes detected temperature data can be significantly reduced.

Embodiment An embodiment of the present invention is shown in FIG. The embodiment will be described using three temperature measurement points as in the conventional example.
1 to 3 are thermistors, 4 is a single resistor, 7 is one voltage comparator, 10 is a microcomputer, 11 is a D/A converter, 12 to 14 are switching elements, 15 is a power supply, and 16 is a voltage comparator 7 Pull-up resistor, 1
9-27 are resistors, 28-39 are LEDs, 40-4
5 and 46 to 51 are diodes and switches, respectively; 52 and 53 are an LED display section and a key input section connected in a matrix and used as a man-machine interface;
56 to 73 are input terminals of the microcomputer 10. As mentioned above, the same parts as the conventional structure are given the same reference numerals and the explanation is omitted.

One terminals of the thermistors 1 to 3 are all connected to a resistor 4 for generating a divided voltage and one input terminal (non-inverting input terminal) of a voltage comparator 7. The other terminals are connected to the switching elements 12-14 via diodes 74-76, respectively.

These switching elements 12 to 14 are connected to the microcomputer 1.
By sequentially setting the output terminals 59 to 61 of 0 to a low level, the LED display section 52 and the key input section 53 are dynamically driven, and voltages are applied to the thermistors 1 to 3 in a time-division manner. In addition, the diodes 74 to 76 prevent current from flowing backward through other thermistors when a voltage is applied to any of thermistors 1 to 3, and are always connected to one of thermistors 1 to 3 and the resistor 4 from an electrical point of view. are made to be equivalent to the state in which they are connected in series.

Next, FIG. 2 shows the voltage waveforms of various parts in this case. V _A , V _B , and V _C are terminal voltages on the diodes 74 to 76 side of thermistors 1 to 3 shown in FIG. 1, respectively, and V _D is a voltage across the resistor 4. Further, a period indicated by I in the figure is a time when switching element 12 is in a conductive state, and similarly, indicates that switching elements 13 and 14 are respectively in a conductive state. That is, during the period, V _A becomes equal to the voltage of the power supply 15 minus the collector-emitter voltage at saturation of the switching element 12 and the forward voltage drop of the diode 74, and similarly,
The magnitudes of V _B and V _C are also equal to this during the period of . During this period, a voltage is applied to only thermistor 1 connected in series with resistor 4, and a voltage V I is generated in resistor 4, which is determined by the resistance value corresponding to the temperature of the location where thermistor ₁ is installed. do. Similarly, during the period, the voltages V〓, V〓 are determined by the resistance values corresponding to the temperatures at the locations where thermistors 2 and 3 are installed, respectively.
occurs in resistor 4.

That is, by adopting such a configuration, temperature information from three temporally distinct locations is input to one voltage comparator 7.

Next, a method for determining temperature will be described. The change in the voltage V F at the output terminal of the voltage comparator 7 due to the change in the voltage V _E at the inverting input terminal of the voltage comparator 7, that is, the voltage at the output terminal of the D/A converter 11 shown in _FIG . Shown in Figure 3.

The microcomputer 10 inputs binary data to the D/A converter 11, and the D/A converter 11 generates as output an analog voltage corresponding to this data. In this embodiment, the output voltage of the D/A converter 11 is gradually increased from zero. However, it is assumed that the period in which the data successively outputted from the microcomputer 10 changes is sufficiently longer than the period from period to.

The voltage V _E at the inverting input terminal of the voltage comparator 7 is the second
When V is less than V shown in the figure, the voltage V _F at the output terminal of voltage comparator 7 is at a high level during all periods as shown in Figure 3 A, but when V _E exceeds V _VF is at a low level only during the period as shown in the figure (b). Further increasing V _E ,
When V F becomes larger than V shown in FIG. 2, V _F becomes low level even during the period shown in FIG. 3 C. When V _E becomes higher and exceeds V 〓, it becomes low level in all periods as shown in d.

The microcomputer 10 receives this V _F as input,
It monitors when this level changes from a high level to a low level in each interval ~, and generates the binary data that the microcomputer 10 outputs to the D/A converter 11 at that time to the resistor 4 during that period. It is processed as an A/D converted value of voltage. The magnitude of the voltage generated across this resistor 4 is determined by the resistance value of the thermistors 1-3 corresponding to the temperature of the location where the thermistors 1-3 are installed.

That is, the installation location of thermistor 1 during the period, the installation location of thermistor 2 during the period,
During the period, temperature detection is performed at each location where the thermistor 3 is installed.

Although only the thermistor has been described in the embodiment, a temperature measurement block combined with one or more resistors that compensates for the linearity of the temperature-resistance characteristic of the thermistor may be used. Furthermore, the thermistor or the temperature measuring block can be connected directly to the switching element.

Effects of the Invention As described above, according to the present invention, multiple temperatures can be detected using one voltage comparator, and although it is functionally the same as the conventional example, 2 voltage comparators, 4 resistors
can be reduced. In addition, accuracy may be required for the resistor connected in series with the thermistor.
The fact that this resistor can also be combined into one has more meaning than simply reducing the number of ordinary resistors. Furthermore, the number of required input terminals of the microcomputer can be reduced by two, and the limited input terminals of the microcomputer can be used for other processing. Furthermore, the applied voltage source for time-division drive is obtained from the dynamic drive switching elements for LED display and key input, resulting in an extremely rational configuration.

As described above, according to the present invention, multiple temperatures can be detected very economically, and this has great industrial significance.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the temperature detection device of the present invention, Fig. 2 is a voltage change diagram of the main parts of the device, and Fig. 3 is a diagram showing voltage changes at the inverting input terminal of the voltage comparator of the device. FIG. 4, which is a diagram showing changes in output terminal voltage, is a circuit diagram showing a conventional example. 1-3...Thermistor, 4...Resistor, 7...Voltage comparator, 10...Microcomputer, 11...D/A converter, 12-14...Switching element, 52...
...LED display section, 53...key input section.

Claims (1)

[Claims] 1. It has a plurality of temperature measurement blocks combined with a thermistor or one or more resistances that compensate for the linearity of the temperature-resistance characteristic of this thermistor,
One terminal of the thermistor or the temperature measuring block is all connected to the same resistor and one input terminal of the same voltage comparator, and the other terminal of the thermistor or the temperature measuring block is connected, respectively, directly or through a diode. It is connected to a switching element for dynamically driving the LED display section or the key input section connected in a matrix, and each of the thermistors or the temperature measurement block is supplied with a voltage synchronized with the dynamic drive in a time-sharing manner. Temperature detection device that applies voltage.