JPS6123931A - Temperature display device - Google Patents

Abstract

PURPOSE:To detect accurate temperature with a small number of parts by switching a temperature display means which displays temperature in N stages and a current temperature detecting means which detects the temperature of a temperature sensitive element in N stages alternately through a switching means. CONSTITUTION:The temperature of the temperature sensitive element 53 is set high in the order of resistances 54, 55 and 56 for temperature detection. When a terminal AA of a microcomputer (microcomputer)51 is held at ''H'' for a specific period, a transistor TR64 turns off and no current flows to an LED for temperature display, so that no display is made. When a terminal BB is held at ''L'' at the same time, a voltage divided through the resistance 54 and element 53 is applied to one terminal of a comparator 57, whose output inversion shows the temperature is higher than temperature determined by the resistance 54. When the output is not inverted, the set temperature of resistances for temperature setting when terminals CC and DD are held at ''L'' successively is regarded as the current temperature. Said operation is repeated at a constant period and the current temperature and temperature by the LED are switched and displayed alternately through the TR64, thereby performing accurate temperature detection.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature display device for an electronic circuit in an electronic device.

Configuration of a conventional example and its problems A conventional temperature display device will be explained with reference to the drawings.

FIG. 1 shows a circuit diagram of a conventional temperature display device. Referring to FIG. 1, 1 is a microcomputer, 2 is a temperature sensing element, and one end of the temperature sensing element is connected to one end of three temperature setting resistors 5, 6.7, and the e terminal of a comparator 8. It is connected. The other ends of the three temperature setting resistors 5, 6.7 are connected to the anodes of diodes 9, 10.11, respectively, and the cathode of diode 9 is connected to an LED for temperature display.
12 cathode, microcomputer 1 AK, diode 10 cathode, temperature display LED 13 cathode, microcomputer 10B, diode 1
The cathode of No. 1 is connected to the cathode of the temperature display LED 14 and C of the microcomputer. One end of a resistor 16 is connected to the anode of the temperature display LEI 12, 13.14.

The connection point between resistors 17 and 18 is connected to the ■ terminal of the comparator 8, the other end of the resistor 17 is connected to ■I11 of the DC voltage 19, and the other end of the resistor 18 is connected to the ○ side of the DC voltage 19. The output of comparator 8 is the microcomputer's D
It is connected to the. The ■ voltage of the DC voltage 19 is connected to the resistor 16, the other end of the temperature sensing element 2, and the microcomputer 10G, and the θ voltage is connected to H of the microcomputer.

The operation of the temperature display device configured as described above will be explained below.

Now, set the resistors so that the detected temperature increases in the order of resistors 5 and 6.7. First, if only the microcomputer (hereinafter referred to as a microcomputer) is set to I L +1, the connection point between the temperature sensing element 2 and the resistor 5 will be determined by the resistance of the temperature sensing element 2 and the forward voltage of the resistor 6 and diode 9. The voltage of
It is applied as a voltage at the C terminal of the comparator 8 and compared with the voltage at the C terminal of the comparator 8. At that time, if the output of the comparator 8 is inverted, it indicates that the temperature is higher than the temperature determined by the resistor 5. If the output is not reversed, only the B terminal and only the C terminal are sequentially set to L'', and the set temperature of the temperature detection resistor when the output is reversed is regarded as the current temperature.

Next, for a certain period of time, if the output, for example, the ``human'' terminal of the microcomputer, is reversed, the output of the input terminal of the microcomputer is set to ``L'', and the current temperature is displayed. , terminal u of microcomputer 1), +1, t+
B IT , 11 G +1 sequentially, L in the above procedure
”, detect the current temperature, and then display the current temperature, which is repeated at regular intervals.

However, in the above configuration, as the number of current temperature displays increases, the diode that prevents current flowing from the current temperature display LED to the temperature setting resistor (see FIG. 1) increases.
．． 10.11 are required as many times as indicated, and the forward voltage of the diode contributes to the temperature detection voltage, so the temperature dependence of the forward voltage of the diodes 9, 10, and 11 is greater than that of the resistance. This has the drawback that the ambient temperature of the circuit changes and current temperature detection becomes uncertain.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned drawbacks and provides a temperature display device that can accurately detect temperature with a small number of parts.

Structure of the Invention To achieve this object, the temperature display device of the present invention includes a temperature sensing element that detects temperature, current temperature detection means that detects the temperature of the temperature sensing element in N stages, and a display device that displays the temperature in N stages. It is composed of a temperature display means that displays the temperature in stages, and a switching means that alternately switches between the temperature display means and the current temperature detection means.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a temperature display device according to an embodiment of the present invention. 61 in Figure 2 is a microcomputer (
(hereinafter referred to as "1 microcomputer"), 52 is a DC power supply, 53 is a temperature sensing element such as a thermistor, one end of which is connected to one end of temperature detection resistor 54, 55, 56 and the C terminal of comparator 57. Resistor 58 is connected to the C terminal of 57.
．． 59 is connected to one end, the other end of the resistor 54 is connected to the cathode of the temperature display LED 60 and the terminal BB of the microcomputer 51, and the other end of the resistor 55 is connected to the cathode of the temperature display LED 61 and the terminal cC of the microcomputer 51. connected, resistor 56
The cathode of the temperature display LED 62 and the terminal DD of the microcomputer 51 are connected to the other end, the output of the comparator 57 is connected to the terminal EE of the microcomputer 51, and the temperature display LED 62 is connected to the terminal DD of the microcomputer 51.
The anodes of '60, 61, and 62 are all connected and connected to one end of the resistor 63, and the other end is connected to the transistor 64.
Its base is connected to one end of resistors 65 and 66, and the other end of resistor 66 is connected to terminal AA of microcomputer 61. , one end of the temperature sensing element 63 and the emitters of the transistors 1 to 4 are connected to the GGC terminal of the microcomputer 51, and one end of the resistor 69 and the microcomputer 61 are connected to the ○ voltage of the DC power supply 62.
The HH terminal of is connected. Reference numeral 67 indicates a current temperature detection means for detecting the temperature of the temperature sensing element 53 in N stages (in the embodiment, 3 stages); 68 indicates a display device consisting of temperature display LEDs 60 to 62; and 69 indicates a display device that detects the temperature in N stages. The temperature display means 7o is a switching means for alternately switching between the temperature display means 69 and the current temperature detection means 67, and has a transistor 64.

The operation of the temperature display device configured as described above will be explained below.

Now, set the temperature detection resistors 54, 55, and 56 to high temperatures in this order.

First, when the terminal AA of the microcomputer is set to "°H" for a certain period of time, the transistor 64 is turned off, and no current flows through the temperature display LED and no display is performed.At the same time, the terminal +l BI3 II of the microcomputer 61 is set to "L"(" cc”.

When 'DD' is set to 'H2'), a voltage divided by the resistor 54 and the temperature sensing element 63 is applied to the ○ terminal of the comparator 57, and is compared with the voltage of the comparator 57.

At that time, if the output of the comparator 57 is inverted, it indicates that the temperature is higher than the temperature determined by the temperature detection resistor 54. If the output is not inverted, the microcomputer 61 terminals CO, I)D
is set to 11 L II, the current temperature is assumed to be the set temperature of the temperature detection resistor when the output is inverted, and the microcomputer terminal ("BB" or II C
C11 or +1 D D 11). Now, suppose that the output is inverted by setting the II B B +1 terminal to tt L++.

Next, set the "person A" terminal to u I, +1, and tt B B
When terminal 11 is set to L'', temperature display LKD60 lights up.The above operation is repeated at regular intervals.
Shorten the current temperature detection time (transistor 6 OFF period) within a certain period, and shorten the temperature display time (transistor 6
If you lengthen the ON period of 4), the temperature display LE will appear to be
D appears to be lit.

That is, the transistor 64 alternately switches between current temperature detection and temperature display.

According to the present invention, by using one switching means, the number of N diodes of the conventional N temperature detection resistors can be eliminated, and the number of parts can be reduced. Temperature changes in the forward voltage can be ignored and the current temperature can be accurately detected, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional temperature display device, and FIG. 2 is a circuit diagram of a temperature display device showing an embodiment of the present invention. 51...Microcomputer, 63...
...Temperature sensing element, 54,55.56...Resistance for temperature detection, 60.61.62...LE for temperature display
D, 57...Comparator, 52...
DC t source. Name of agent: Patent attorney Toshio Nakao and one other person - Figure 1

Claims (1)

[Claims] A temperature sensing element that detects temperature, a current temperature detection means that detects the temperature of the temperature sensing element in N stages, and a display device that displays the temperature
A temperature display device comprising a temperature display means that displays the temperature in stages, and a switching means that alternately switches between the temperature display means and the current temperature detection means.