JPH0436624A - Temperature display unit circuit - Google Patents

Abstract

PURPOSE:To improve the display unit circuit by providing a switch part, a display part which turns on a pilot lamp according to a specific temperature range, and a detection control part which controls the illumination of the pilot lamp according to the specific temperature range. CONSTITUTION:When the temperature rises to specific temperature, e.g. 100 deg.C, the resistance of an NTC type thermistor 11 decreases and when the resistance value reaches a specific values, a transistor (TR) 12 operates to make the current from a power source VB flow from an emitter 12c(VD) to the display part 20. The current from the display part 20 flows from respective a fixed resistance 26a to the earth 31 through the NTC type thermistor 11. When the temperature further rises to specific temperature, e.g. 160 deg.C, the current flows to the earth through the PTC type thermistor 15 and light emitting diode 21 of the detection control part 30, so that the light emitting diode 21 illuminates corresponding to a temperature of 160 deg.C. Thus, the PTC type thermistor 15 is used to turn on and off the power source at need, the operation of the device is facilitated, and the power source is prevented from being left ON forgetfully.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a temperature display circuit, and more particularly to an improvement in a temperature display circuit that displays temperature using a display section corresponding to the temperature.

(Prior Art) Conventionally, as a device for displaying temperature using a display unit corresponding to temperature, there is a thermometer using a bimetal or a comparison circuit using a thermistor as shown in FIG. 4. In FIG. 4, the entire device includes a power switch section 50, a detection section 60 that detects temperature, a display section 70 that lights up an indicator light according to a predetermined temperature range, and a control section 80 that controls lighting within the temperature range. , power supply 9 (not shown)
It is composed of 0 and . The power switch section 50 mainly consists of a switch 51 and a flip-flop 52, and the detection section 60 consists of an NTC type thermistor 61 and an amplifier 62.
In addition, the display section 70 includes four light emitting diodes 71, 72, 73, and 74 corresponding to a predetermined temperature, for example, 160° C., 175° C., 190° C. and 1220° C., and a fixed resistor 75. 76, 77, and 78, and the control unit 80 further includes four comparators 81, 82, 83, and 84 corresponding to a predetermined temperature, and five resistors 85, 86, and 87 for temperature setting. It consists of .88.89.

(Problem to be Solved by the Invention) However, the above-mentioned conventional device using bimetal has poor accuracy. Furthermore, the conventional configuration shown in FIG. 4 requires a manual switch to turn the power off and on, and requires a large number of components in the comparison circuit. Furthermore, since it is a manual switch, it is cumbersome to have to turn it on during measurement, and if you forget to turn it off, the battery will run out. Furthermore, since a high-precision IC is used to improve accuracy, there are problems in that the cost is high, it is difficult to use in adverse environments (for example, high temperature, water), and durability is poor.

The present invention has focused on the above-mentioned conventional problems, and relates to a temperature display circuit, and particularly aims to improve a temperature display circuit that displays temperature using a display section corresponding to the temperature.

(Means for Solving the Problems) In order to achieve the above object, in a first aspect of the present invention, in a temperature display circuit that displays temperature using a display section corresponding to temperature, a switch section and a predetermined It consists of a display section that lights up the indicator light according to the temperature range, and a detection control section that detects the temperature and controls the lighting of the indicator light according to the predetermined temperature range.

In a second invention based on the first invention, a PTC thermistor is used in the detection control section, and in a third invention, an NTC thermistor is used in the switch section to automatically turn on the power.

(Function) According to the above configuration, since the PTC type thermistor is used, the power can be turned off and on when necessary, so the operation is easy and there is no need to forget to turn off the power. Furthermore, costs are reduced because the number of parts is reduced. Furthermore, since no IC is used, it can be used even under adverse environments (eg, high temperature, water).

(Example) Hereinafter, an example of a temperature indicator circuit according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a temperature indicator according to an embodiment of the present invention. In Figure 1,
The present invention includes a switch section 10 that can automatically turn on and off, a display section 20 that turns on an indicator light according to a predetermined temperature range, and a display section 20 that detects temperature and turns on an indicator light according to a predetermined temperature range. It is composed of a detection control section 30 that controls the detection control section 30, and a power supply 40 (not shown). The switch section 10 consists of one NTC type thermistor 11 and a transistor 12. One pole 11a of the NTC type thermistor 11 is connected to the base 12a, the other positive pole llb is connected to the collector 12b of the transistor 12, and the collector 12b is connected to the base 12a. It is connected to a power source 40 (Vs), not shown. transistor 1
The second emitter 12c (V,) is connected to the display section 20.

The display unit 20 displays a temperature corresponding to a predetermined temperature, for example, 160°C,
Three 16s corresponding to 175℃, 190℃, 220℃
Light emitting diode (LED) at 0℃, 175℃, 190℃
2! , 22, 23, one buzzer 24 compatible with 220°C, and a transistor 25 that amplifies the power to the buzzer 24.
and fixed resistors 26a and 26b, and the emitter 1
2c (V, ) are connected to the detection control unit 3o through series-connected fixed resistors 26a and 26b, respectively.
is connected to. In addition, light emitting diodes 21, 22.
The anode of 23 is connected to the connection between the fixed resistor 26a and each detection control unit 30, and the cathode is connected to the ground. Furthermore, the detection control section 3o is made up of four PTC type thermistors 15, 16, 17 and I8, one of which is connected to the display section 2o and the other to the ground 31.

In the above configuration, the operation will be explained next.

The temperature increases until it reaches a predetermined temperature, e.g. l 00 'C.
When it reaches, the NTC type thermistor 1 as shown in Fig.
When the resistance of the transistor 12 decreases to a predetermined value, a current flows to the base 12a of the transistor 12, and the transistor 12 is activated to turn on the switch, and the current from the power source 40 (Ve) flows from the emitter 12c (Vo) to the display section 20. The current from the display section 2o flows from each fixed resistor 26a to the ground 31 via the PTC type thermistor 11. Furthermore, when the temperature increases and reaches a predetermined temperature, for example 160°C,
The resistance of the PTC type thermistor 15 of the detection control unit 30 is the third
The current increases as shown in the figure, and the current flowing to the ground 31 is cut off, and the current flows to the ground via the light emitting diode 21. As a result, the light emitting diode 21 lights up in accordance with the temperature of 160°C. Furthermore, as the temperature rises, similarly, the light emitting diode 22 is turned off in response to a temperature of 175°C, and the light emitting diode 2 is turned off in response to a temperature of 190°C.
3 lights up. When the temperature reaches 220℃, PT
The resistance of the C-type thermistor 15 increases as shown in FIG.
The current flowing to the ground 31 is cut off, the current flows from the base of the transistor 25 to the emitter, the transistor 25 is activated, and the buzzer 24 corresponding to 220° C. sounds, indicating that the temperature has reached the warning point. At this time, the light emitting diodes 21 and 22 are set to green for safety, the light emitting diode 23 is set to yellow for caution, and the light emitting diode 24 is set to yellow for caution.
It is also possible to indicate a warning by making it red.

Furthermore, although a thermistor is used in the switch section, a normal switch may be used to turn on the switch during measurement. Furthermore, although four temperatures were detected in the above embodiment, it goes without saying that the number is not limited.

(Effects of the Invention) As explained above, according to the present invention, the power can be turned off and on when necessary, making operation easier and eliminating the need to forget to turn off the power. Costs are reduced because the number of parts is reduced. Furthermore, since no IC is used, an excellent effect can be obtained in that it can be used even under adverse environments.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a temperature indicator according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between temperature and resistance of an NTC type thermistor. FIG. 3 is a diagram showing the relationship between temperature and resistance of a PTC type thermistor. FIG. 4 is a circuit diagram of a temperature indicator according to a conventional embodiment. 20 ・ ・ 24 ・ ・ 6 al 30 ・ ・ 3 l ・ ・Power switch section, ・NTC type thermistor, 5...Transistor, 6.17.18...PTC type thermistor, ・Display section, 2.23・Buzzer 26b...Fixed resistance, ・Detection control section, Earth, Light emitting diode,

Claims (3)

[Claims] (1) In a temperature display circuit that displays temperature using a display section corresponding to the temperature, there is a switch section, a display section that lights up an indicator light according to a predetermined temperature range, and a switch section that detects the temperature and turns on an indicator light according to a predetermined temperature range. a detection control unit that controls lighting of the indicator light;
A temperature indicator circuit comprising: (2) The temperature indicator circuit according to claim (1), wherein a PTC type thermistor is used in the detection control section. (3) The temperature indicator circuit according to claim (1), wherein the switch part uses an NTC type thermistor to automatically turn on the power.