CN2755660Y

CN2755660Y - Small thermostat source

Info

Publication number: CN2755660Y
Application number: CN 200420055033
Authority: CN
Inventors: 杜方迅
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-20
Filing date: 2004-12-20
Publication date: 2006-02-01
Anticipated expiration: 2014-12-20

Abstract

The utility model relates to a thermostat source which can be used for standardizing the normal temperature of thermometers and like instruments. The utility model uses a PIC12F629 SCM as a core. An A/D module in the structure of a comparator in the SCM is used for collecting temperature input signals converted by a TMP37 temperature sensor. A D880 large power triode is heated to a preset temperature by control signals output by the pulse width modulation (PWM) processing of the SCM to the D880 large power triode. The operating course of the thermostat source is controlled by the program of the SCM. The utility model has the advantages of low cost, small size, light weight, quick start, short temperature regulation period, etc. Particularly, the cost of the thermostat source is about 10 yuan (RMB) which is less then one thousandth of the cost of a black body radiation thermostat source.

Description

A kind of miniature constant temperature source

Technical field

The utility model relates to a kind of constant temperature source, and particularly a kind of to have a volume little, in light weight, starts the miniature constant temperature source of characteristics such as fast, that the temperature adjustment cycle is short, cost is low.This miniature constant temperature source can be used as the standard temperature source of demarcating infrared thermometer and similar thermometric instruments.

Background technology

Demarcating temperature is a kind of frequent and important work for thermometric instruments, yet temperature calibration needs a kind of standard temperature source.In the past in the known technology, the instrument of demarcating temperature had a lot, use always no more than the blackbody radiation constant temperature source.This constant temperature source is made of a king-sized ironcasting usually, and its surface scribbles black matrix, puts it in the waters then and heats, and makes ironcasting carry a large amount of heats.In order to obtain the constant temperature effect, on ironcasting, offer an aperture since the hole in environment be subjected to external interference little, so with it as the constant temperature point.Facts have proved in the past, although the blackbody radiation constant temperature source is particularly suitable for demarcating infrared thermometer and similar thermometric instruments, but also there is certain defective in it, slow such as heaviness and starting, particularly up to the price of tens thousand of units, not only increased the production cost of temperature Instrument, and it has been applied be subjected to considerable restraint.

Now, development along with computing machine and control technology, people utilize single-chip microcomputer, temperature sensor, A/D change-over circuit, D/A change-over circuit and heater element, making up a constant temperature source from hardware point of view can realize, yet the key of problem is: wanting to design a kind of is small-sized, the simple type constant temperature source of core with the single-chip microcomputer, and it is little, in light weight to have a volume, starts characteristics such as fast, that the temperature adjustment cycle is short, cost is low, has great difficulty technically.With regard to present disclosed prior art, the Shang Weiyou report.

Summary of the invention

It is miniaturization, the simple type constant temperature source of core with the single-chip microcomputer that the purpose of this utility model provides a kind of.

For achieving the above object, the technical solution adopted in the utility model is: a kind of miniature constant temperature source, comprise PIC12F629 type single-chip microcomputer, temperature sensor, RC integrating circuit, RC filtering circuit and large power triode, and its annexation is as follows:

(1), the temperature sensor heat radiator of being close to large power triode is installed the first digit input/output end port of its output voltage signal termination single-chip microcomputer;

(2), the RC integrating circuit is made of resistance R 1 and capacitor C 1, power supply is through resistance R 1 and ground connection after capacitor C 1 is connected, the voltage signal end of integrating capacitor C1 connects the second digit input/output end port of single-chip microcomputer through resistance R 3;

(3), the RC filtering circuit is made of resistance R 2 and capacitor C 2, the third digit input/output end port one tunnel of single-chip microcomputer connects the base stage of large power triode through resistance R 2, another road is through capacitor C 2 ground connection;

(4), the grounded emitter of large power triode, collector connects power supply.

The related content of technique scheme is explained as follows:

1, PIC12F629 type single-chip microcomputer is that Mictochip company produces, and it has only eight pins, only needs 35 individual characters (14) instruction, is that the sparrow may be small but it has all the vital organs, is single-chip microcomputer worthy of the name, is particularly suitable for constructing embedded system.This single-chip microcomputer can be by writing internal register, six the digital input/output port (I/O port) in eight pins defined (one of two other pin is feeder ear V _DD, another is earth terminal V _SS), that is to say can be that output port or input end use with these port definitions.Except the digital input/output port (I/O port) that can be set to standard, many pin also have multiplexing function, and they are:

(1) six standard digital input/output port GPIO port;

(2) two timer/counter TMR0 and TMR1;

(3) analog comparator Comparator;

(4) internal point scratch pad memory EEPROM.

2, in the such scheme, heater element adopts large power triode, such as adopting the D880 large power triode.This large power triode is used in the mu balanced circuit of big electric current usually, because electric current is bigger, heat radiator is housed on the D880.Here use the spinoff that it itself generates heat by big electric current the time, and the positive correlation characteristic of thermal value and electric current, D880 is used as the heater element of constant temperature source.Current amplification factor β=100 of D880.

3, in the such scheme, temperature sensor is as a kind of transducer, and it can be converted into voltage with the heat that heater element produces, and is voltage output type temperature sensor such as the TMP37 that adopts AnalogDevices company to produce.It has the good linearity, sees shown in Figure 3ly, can be used as the direct input of A/D converter in the single-chip microcomputer, and need not pass through amplification process.

4, in the such scheme, for the displays temperature value, a display can also be set, the 4th of single-chip microcomputer is connected with display with the 5th digital input/output end port.Described display can adopt four LCD of SMS0401LCM.

The utility model principle of work is: with the PIC12F629 single-chip microcomputer is core, utilize the temperature input signal of the A/D module collecting temperature sensor conversion of comparer structure in the single-chip microcomputer, pulse-width modulation PWM processing through single-chip microcomputer outputs control signals to large power triode, makes its heating to given temperature.The course of work of constant temperature source is controlled by the program of single-chip microcomputer.

Because the technique scheme utilization, the utility model compared with prior art has following characteristics:

1, from technical standpoint, core technology of the present utility model is the PIC12F629 single-chip microcomputer that the adopted controller as constant temperature source.As everyone knows, in many application and design, all to use data acquisition and control in real time, yet not see on the market being specifically designed to and gather the chip that adds control.If adopt A/D modular converter, D/A modular converter and necessary intelligent chip to realize same function respectively, to the waste of resource and fund, cost is corresponding will to be improved beyond doubt.In this programme design, the input and output side of PIC12F629 single-chip microcomputer does not have special A/D modular converter, D/A modular converter, but utilizes built-in analog comparator of single-chip microcomputer and timer and RC integrating circuit to construct a simple integral formula A/D modular converter; And defined a width modulation (PWM) module at the single-chip microcomputer in house software, made single-chip microcomputer export the square wave in certain pulsewidth and cycle, after RC filtering, obtained direct current signal, in fact finished the D/A translation function.Therefore, we can say does not have special A/D modular converter, D/A modular converter in this programme hardware design, is minimum control system truly.

2, the utility model utilizes the spinoff that large power triode itself generates heat by big electric current the time, and the positive correlation characteristic of thermal value and electric current, the heater element of large power triode as constant temperature source used, not only simple and reliable for structure from the effect aspect, and also cost is very low.

3, the utility model have compared with prior art that cost is low, volume is little, in light weight, start advantages such as fast, that the temperature adjustment cycle is short.Particularly its cost is only about ten yuan, less than the per mille of blackbody radiation constant temperature source.

Description of drawings

Accompanying drawing 1 is the utility model circuit structure diagram;

Accompanying drawing 2 is the utility model simple integral formula A/D transfer principle figure;

Accompanying drawing 3 is TMP37 temperature sensor voltage and temperature linearity graph of a relation;

Accompanying drawing 4 is the utility model software flow pattern;

Accompanying drawing 5 is the utility model interrupt service subroutine process flow diagram.

Embodiment

Below in conjunction with drawings and Examples the utility model is further described:

Embodiment: shown in accompanying drawing 1, a kind of miniature constant temperature source is made up of PIC12F629 type single-chip microcomputer, TMP37 voltage output type temperature sensor, RC integrating circuit, RC filtering circuit, D880 large power triode, four LCD of SMS0401LCM and setting button K.

PIC12F629 type single-chip microcomputer has eight pins as the controller of constant temperature source, and wherein six is digital input/output port GP0～GP5, and one is feeder ear V _DD, another is earth terminal V _SS

The TMP37 temperature sensor is close to the heat radiator installation of D880 large power triode, the first digit input port GP0 of its output voltage signal termination single-chip microcomputer, and the heat that large power triode is produced is converted into voltage signal.

Single-chip microcomputer utilizes its built-in analog comparator and timer and RC integrating circuit to be configured to a simple integral formula A/D modular converter.The RC integrating circuit is made of resistance R 1 and capacitor C 1, and power supply is through resistance R 1 and ground connection after capacitor C 1 is connected, and the voltage signal end of integrating capacitor C1 meets the second digit input/output end port GP1 of single-chip microcomputer through resistance R 3.Specific as follows: see shown in Figure 2, the digital input/output end port GP0 of PIC12F629 single-chip microcomputer, GP1, GP2, these three terminals also can be used as analog comparator usefulness except the digital input/output end port that can be used as standard, wherein:

GP0: the input end (+) of comparer, the voltage signal that transmits is sent in the change of jointing temp sensor;

GP1: the input end (-) of comparer connects the voltage signal of integrating capacitor;

GP2: the output terminal of comparer.

The course of work of simple integral formula A/D modular converter is as follows:

1, definition GP1 is output, and " 0 " is write GP1, capacitor C 1 is thoroughly discharged, simultaneously Timer content clear 0;

2, definition GP1, GP0 is the analog comparator input, and capacitor C 1 begins charging, and the voltage on the capacitor C 1 is:

U_{c} = V_{cc} (1 - e^{- \frac{1}{RC}})

As long as it is appropriate that resistance R 1, capacitor C 1 are selected, Uc just can be directly proportional with integral time.Meanwhile, start Timer T0.When the comparer both end voltage equates, stop counting, this moment, the content Count of Timer in fact just was detected value this moment.

Single-chip microcomputer utilizes width modulation (PWM) module and the RC filtering circuit of its inner definition to construct a D/A modular converter, be specially: single-chip microcomputer inside by software definition a width modulation (PWM) module, can make single-chip microcomputer digital output port GP5 export the square wave in certain pulsewidth and cycle by writing internal register ccpr11 or ccpr21, behind the RC filtering circuit, export direct current signal.PWM (width modulation)+FILTER (filtering) has in fact finished the function of D/A conversion.The RC filtering circuit is made of resistance R 2 and capacitor C 2, and the third digit input/output end port GP5 one tunnel of single-chip microcomputer connects the base stage of large power triode through resistance R 2, and another road is through capacitor C 2 ground connection; The grounded emitter of large power triode, collector connects power supply.

For the displays temperature value, constant current source is provided with four LCD of SMS0401 LCM, and the detected value when stablizing can pass through four liquid crystal display displays of SMS0401 LCM.This display only takies two digital quantity output port GP3, GP4 of single-chip microcomputer.For display, CLK: serial data input; SDI: serial-shift pulse input.The great so limited interface resource of single-chip microcomputer of having saved.Its address mapping table is as follows:

LCDBUF	D7	D6	D5	D4	D3	D2	D1	D0
LCDBUF	D7	D6	D5	D4	D3	D2	D1	D0	0	A1	B1	C1	D1	E1	F1	G1	H1
1	A2	B2	C2	D2	E2	F2	G2	H2	0	A1	B1	C1	D1	E1	F1	G1	H1
1	A2	B2	C2	D2	E2	F2	G2	H2	2	A3	B3	C3	D3	E3	F3	G3	H3
3	A4	B4	C4	D4	E4	F4	G4	H4	2	A3	B3	C3	D3	E3	F3	G3	H3

The input/output end port GP2 of single-chip microcomputer is connected with a setting button K.

In a word, used 4 digital input port GP0, GP1, GP2, GP5 in the single-chip microcomputer, wherein have 3 with A/D, D/A multiplexing.These digital input ports are used as the setting value of man-machine conversation port processing desired temperature, pid parameter.Used 2 digital output port GP3, GP4 in the single-chip microcomputer, be used as of the demonstration of man-machine conversation port various parameters.

The control principle of present embodiment is as follows:

The inside of PIC12F629 single-chip microcomputer by software construction a width modulation (PWM) module.PWM single-chip microcomputer digital output port GP5 exports the square-wave signal in certain pulsewidth and cycle, after RC filtering, export direct current signal, can control by D880 large power triode average current size, when the electric current by triode reaches certain value, triode just begins heating, and its heat is absorbed by heat-conducting glue and heat radiator metallic object on every side soon simultaneously.The TMP37 temperature sensor is close on the heat radiator metallic object, it can become detected temperature transition voltage signal to send simple integral formula A/D modular converter to, and with after the desired temperature of user input is compared, the dutycycle of adjusting PWM promptly changes the electric current of D880 large power triode.As voltage u of single-chip microcomputer output _o, just can produce less current i at base stage b _b, because the amplification of triode just can obtain bigger collector current i _cAnd heat radiator is generated heat.So, T=f (u _o).The temperature of heater element and heating current have just been realized a mobile equilibrium like this, make temperature of heating elements stable.

The user can change desired temperature by the button on the system interface, and more revaluate can show in real time by four LCD of SMS0401 LCM, through a less temperature adjustment cycle, just reaches temperature constant state again.Internal electrical scratch pad memory EEPROM, the last time setting value of temperature that can recording user.Automatically be that desired temperature is controlled with this temperature during start, up to there being new temperature value to write.

The present embodiment software scenario is seen Fig. 4 and Fig. 5, but need to prove: 1, general temperature acquisition sensor is not linear, and present embodiment so the software realization is just fairly simple, has been avoided a lot of computation processes because the TMP37 temperature sensor that uses has the good linearity.2, system uses INT1 and interrupts being used for allowing the user set desired value.3, interrupt service subroutine of every execution, desired temperature increases or reduces 0.1 ℃.System can be that target is regulated with new temperature desired value then.

Claims

1, a kind of miniature constant temperature source, it is characterized in that: comprise PIC12F629 type single-chip microcomputer, temperature sensor, RC integrating circuit, RC filtering circuit and large power triode, its annexation is as follows:

(2), the RC integrating circuit is made of resistance [R1] and electric capacity [C1], power supply is through resistance [R1] and ground connection after electric capacity [C1] is connected, the voltage signal end of integrating capacitor [C1] connects the second digit input/output end port of single-chip microcomputer through resistance [R3];

(3), RC filtered electrical routing resistance [R2] and electric capacity [C2] constitutes, the third digit input/output end port one tunnel of single-chip microcomputer connects the base stage of large power triode through resistance [R2], another road is through electric capacity [C2] ground connection;

2, miniature constant temperature according to claim 1 source is characterized in that: also comprise a display, the 4th of single-chip microcomputer is connected with display with the 5th digital input/output end port.

3, miniature constant temperature according to claim 2 source is characterized in that: described display adopts four LCD of SMS0401LCM.

4, miniature constant temperature according to claim 1 source is characterized in that: described temperature sensor adopts TMP37 voltage output type temperature sensor.

5, miniature constant temperature according to claim 1 source, it is characterized in that: described large power triode is the D880 large power triode.