CN201811809U

CN201811809U - Temperature detection circuit

Info

Publication number: CN201811809U
Application number: CN2010205330293U
Authority: CN
Inventors: 姚国祥; 张银波
Original assignee: NINGBO SHUNYUN ELECTRONIC CO Ltd
Current assignee: NINGBO SHUNYUN ELECTRONIC CO Ltd
Priority date: 2010-09-15
Filing date: 2010-09-15
Publication date: 2011-04-27
Anticipated expiration: 2020-09-15

Abstract

The utility model discloses a temperature detection circuit applied in home appliances. A port, connected with a temperature sensor, of a conventional integrated circuit is an A/D port; and if a temperature is detected by using the A/D port, programming difficulties are greater than using a common I/O port. The temperature detection circuit is characterized by comprising an integrated circuit, a resistor, a negative temperature coefficient (NTC) thermal resistor and a capacitor, wherein the integrated circuit comprises three I/O ports, namely a Port 1, a Port 2 and a Port 3 respectively; the Port 1 and the Port 2 are connected with the NTC thermal resistor and the resistor respectively; the NTC thermal resistor, the resistor and the Port 3 are connected with the capacitor in series after being connected in parallel; and the other end of the capacitor is grounded. In the temperature detection circuit, the resistance characteristics of the NTC thermal resistor and the resistor-to-capacitor charge-discharge time are utilized, so that the acquisition of the temperature is realized by the common I/O port of a singlechip.

Description

A kind of temperature sensing circuit

Technical field

The utility model relates to the circuit of household electrical appliance, specifically a kind of temperature sensing circuit that is applied in the household electrical appliances.

Background technology

Along with the arrival of new technology revolution, the whole world begins to enter the information age.In utilizing the process of information, what at first will solve is exactly how to obtain information accurately and reliably, and sensor is main path and means of obtaining information in nature and the production field; Just because of these characteristics of sensor, make that the utilization of sensor is extensive gradually.

In household appliances, the application of sensor makes product have more robotization and hommization, has also made very important effect for the class that promotes product.In sensor, utilization will be counted temperature sensor and gas sensor the most widely.Such as serviceability temperature sensor in the lampblack absorber series products (NTC themistor commonly used) and gas sensor, make and product robotization more when ambient temperature is higher than a certain setting value or smog is arranged, can realize opening actions such as motor automatically.The interface that existing integrated circuit is connected with temperature sensor is necessary for the A/D mouth, but be not that each integrated circuit all exists the A/D mouth, perhaps in some complicated control system, the A/D mouth is not enough, be replaced with the integrated circuit that has the A/D mouth or have more A/D mouths, will certainly cause increasing substantially of cost; And if adopted the A/D mouth to come detected temperatures, the programming difficulty would be than big with common I/O mouth.

The utility model content

Technical problem to be solved in the utility model is to overcome the defective that above-mentioned prior art exists, a kind of temperature sensing circuit that is connected with temperature sensor with the common I/O mouth of integrated circuit is provided, to save cost and to reduce the difficulty of programming, make full use of the resource of integrated circuit.

For this reason, the technical solution adopted in the utility model is: a kind of temperature sensing circuit, it is characterized in that it comprises integrated circuit, a resistance, a NTC themistor and an electric capacity, described integrated circuit has three I/O mouths, be respectively Port1 mouth, Port2 mouth and Port3 mouth, Port1 mouth, Port2 mouth connect NTC themistor and resistance respectively, after NTC themistor, resistance and the parallel connection of Port3 mouth and capacitances in series, and the other end ground connection of electric capacity.It (is that temperature is when low that the utility model utilizes the resistance characteristic of NTC themistor (negative temperature coefficient thermistor), its resistance value is higher, along with the rising of temperature, its resistance value reduces) and time of discharging and recharging of resistance capacitance realize of the collection of the common I/O mouth of single-chip microcomputer to temperature.

When the detected voltage of Port3 mouth rises to the minimum high level of integrated circuit or drops to high-low level of integrated circuit, Port3 mouth state will change, become high level or become low level from low level, thereby realized the analog quantity of temperature variation is become the variation that integrated circuit can detected digital quantity from high level.

What integrated circuit adopted is single-chip microcomputer, and the power consumption of circuit is little, the reliability height.

The utlity model has following beneficial effect.

1, circuit reliability can be high, under the situation of line voltage with ± 15% fluctuation, still can effectively work.

2, highly versatile not only can be realized the purpose of image data to NTC themistor, can also realize the purpose of image data to other sensors of the same type, required adjustment only be the resistance (according to the parameter adjustment of used sensor) of resistance.

3, circuit is simple, and hardware circuit only is made of resistance, electric capacity, NTC themistor, does not have other integrated circuit except that single-chip microcomputer, and is with low cost, can produce the certain economic effect.

4, low-power consumption, energy-conservation.

The utility model is described in further detail below in conjunction with specification drawings and specific embodiments.

Description of drawings

Fig. 1 is circuit theory diagrams of the present utility model.

Embodiment

As shown in Figure 1, temperature sensing circuit is made up of integrated circuit, a resistance, a NTC themistor and an electric capacity, described integrated circuit has three I/O mouth Port1 mouths, Port2 mouth and Port3 mouths, Port1 mouth, Port2 mouth connect NTC themistor and resistance respectively, connect with capacitor C 1 after NTC themistor, resistance R 1 and the parallel connection of Port3 mouth, the other end ground connection of capacitor C 1, the Port3 mouth is used for detecting the voltage of C1.The resistance of resistance R 1 is that the parameter of 10K Ω ± 1%, NTC themistor ZNR1 is R25 ℃=10K Ω ± 5%, and the capacity of B25/50=3950 ± 5% and capacitor C 1 is 0.22 μ F.About how choosing the resistance of R1, be to decide according to the parameter of used thermistor; When temperature was 25 ℃, the resistance of thermal resistor was 10K Ω, and the resistance of therefore choosing R1 here is 10K Ω; The resistance error that is noted that resistance R 1 should be the smaller the better, at ordinary times the resistance error of usefulness be generally ± 5%, based on to the accuracy of capacitor charge and discharge time and the consideration of cost, the resistance error of the resistance of power taking here R1 is ± 1%.

The course of work of the present utility model is as follows: the Port1 mouth output low level of integrated circuit (being single-chip microcomputer), and during Port2 mouth output high level, single-chip microcomputer is by 1 charging of 1 pair of capacitor C of resistance R, charging rate τ=R1*C1; And the voltage of Port3 mouth is the voltage at capacitor C 1 two ends; When just having begun electric capacity charged, the voltage at electric capacity two ends is 0, and this moment, the state of single-chip microcomputer Port3 mouth was a low level, when the voltage at electric capacity two ends since electric capacity charge to the minimum high level of used single-chip microcomputer the time, the state of single-chip microcomputer Port3 mouth jumps to 1 by 0, promptly becomes high level from low level; Single-chip microcomputer can and be stored the time T 1 of Port3 mouth by 0 change, 1 this process by inner timer record; When making Port2 mouth output low level, capacitor C 1 is by the R1 discharge, and the state that is discharged to single-chip microcomputer Port3 mouth jumps to 0 by 1, writes down T2 discharge time of capacitor C 1 equally; This moment, the voltage at electric capacity two ends still was 0, now make the square-wave signal of single-chip microcomputer Port1 output one-period T ＇ (T ＇ is greater than 1.5 times of T1), when being in the high level of square-wave signal, single-chip microcomputer charges to capacitor C 1 by ZNR1, record single-chip microcomputer Port3 mouth by the time T of low transition to high level; Because the characteristic of ZNR1, promptly the temperature when detection is low more, and resistance is high more; When ambient temperature was 25 ℃, the resistance of ZNR1 was 10K Ω; According to capacitor charging time constant τ=R*C as can be known, when R is big more, τ is big more; Can get thus, when T 〉=T1, the detected temperature of thermal resistor≤25 ℃ is described; When T≤T1, the detected temperature of thermal resistor 〉=25 ℃ is described; So the R value according to T draws thermistor draws the ambient temperature value through the R-T of thermal resistor curve map.

Claims

1. temperature sensing circuit, it is characterized in that it comprises integrated circuit, a resistance, a NTC themistor and an electric capacity, described integrated circuit has three I/O mouths, be respectively Port1 mouth, Port2 mouth and Port3 mouth, Port1 mouth, Port2 mouth connect NTC themistor and resistance respectively, after NTC themistor, resistance and the parallel connection of Port3 mouth and capacitances in series, the other end ground connection of electric capacity.

2. temperature sensing circuit according to claim 1 is characterized in that described integrated circuit is a single-chip microcomputer.