1、-1- AT89C51 single-chip temperature-controlled water temperature control system Early contact thermometers for chemical water temperature thermostat shortcomings, this paper introduces an approach based on AT89C51 single-chip microcomputer-based controller, combined with integrated temperature senso
2、r AD590J composed of constant temperature water temperature control system. Chemical, chemical experiments and research on water temperature requirements of high performance and accuracy, the current market face chemistry, chemical experiments and study the high price of heated water systems. In thi
3、s paper, the design of single-chip component AT89C51 from the temperature control system for people with low-cost, high precision, intelligent control, etc. The water temperature of the performance indicators are: Temperature range: 0 1O0 ； temperature range: 0 99.9 ； temperature: 0.4 ； heating powe
4、r: 1000W. Part of the hardware circuit AT89C51 selected as the system CPU, it is a low-power, high performance, 4kB flash chip programmable / erasable read-only memory 8-bit microcontroller COMS. Block diagram of the system AT89C51 single-chip by chip, IO expansion port 8255 chip, 8032 chip digital-
5、to-analog conversion, analog-to-digital conversion chip 0809, keyboard control, status indication circuit, sampling circuit temperature thermostat control circuit, driver circuit and display circuit, such as group into. 1.1 temperature sampling circuit Temperature sampling circuit using AD590 curren
6、t-mode temperature-sensitive device of its stability and linearity are better. When in AD590 for the current 273.2uA, temperature increase 1 , the current increase in 1uA. The current is converted to voltage signal by analog-to-digital converter ADC0809, AT89C51 single-chip temperature monitoring an
7、d conversion. One resistor R measurement using a low temperature coefficient of resistance, temperature coefficient of 10 x l0_6 / . When monitoring the temperature of lO0 when generated in the resistor voltage 18.66V about, when the temperature is 0 when generated in the resistance of about 1 3.66V
8、 voltage, that is, at a temperature of 0 1O0 in resistance on pressure drop -2- resulting from bad to 5v. However, when the temperature is 0 demodulation IC2 potential output allows for OV, the time when 1O0 for IC2 output 5v, in the constant temperature water tank 3 installed AD590, which are locat
9、ed under the sink in the various parts, using its monitoring of temperature changes in the market tank in order to control the stirring motor to ensure uniform temperature sink. 1.2 thermostat control circuit Constant temperature control circuit from heating thermostat temperature setting and the co
10、mposition of the two parts of the circuit. The thermostat circuit settings temperature to provide the working conditions of the heating circuit, the circuit set by the keyboard combination of software programming to achieve common. In addition to each button and set the IO port connected to 8255, bu
11、t also through a door with the AT89C51 and T0 timer connected so that when the button is depressed immediately after the interruption to the application AT89C51, 8255 inquiry, and at the same time the functions of the corresponding control . One set is the key type from the set and the AT89C51, D /
12、A converter analog voltage measurement is the AD590, after the detection signal AT89C51, D / A converter provides analog, IC3 constitute a comparison amplifier, IC4 ratio amplifier , BG1, BG2, T constitutes a thyristor conduction angle control circuit, a single bipolar transistor oscillator circuit
13、the lower the frequency, SCRs on-the shorter the time the smaller the heating power, on the contrary higher. Single-junction transistors and the oscillation frequency by the ratio of amplifier output voltage control, AT89C51 single-chip temperature settings through the sample and the temperature dif
14、ference after the value, after amplification by comparison with the temperature change to mediate voltage thyristor the conduction angle in order to achieve the adjustment of heating power to meet the temperature requirements of the waters of the thermostat. 1.3 Drive Circuit When the 8255 high outp
15、ut corresponding IO port, the drive transistor turn-on 9013, so that the relay action, in order to drive the work of the relevant circuit. Significant choice for a show so that the display to choose between the settings and measurement. 1.4 Keyboard control and status indication circuit With the 825
16、5 connected to the IO port 8 and 9 LED button to complete the common waters of the control thermostat and the instructions state. In addition to each -3- button with the 8255 connected to the IO port, but also with AT89C51 it connected the timer so that when the button is depressed immediately after
17、 the interruption of AT89C51 applications, and query the status of 8255 in order to carry out the functions of the corresponding control. 1.5 shows the circuit Display circuit using a half the number of table 4 show the temperature head waters of the measurement of temperature and set temperature. 2
18、 Software design Skeleton of the software, contains initialization, configuration subroutine, subroutines to deal with temperature, showing subroutine. Completion of system initialization after power-on reset 8255 and software initialization and pre-heated water for the water to wait for work, and o
19、pen the inlet solenoid valve, when the corresponding button press interrupted when AT89C51, read 8255 the status of the population to determine the function keys in order to call the corresponding subroutine. Subroutine completed one set of the set temperature function. Initialization settings for t
20、he 0o.0o, when the choice set and to identify key addition and subtraction operations for each click on the Settings button software settings for the corresponding temperature of the addition and subtraction operation count, and the value storage and display. Subroutine to deal with the role of temp
21、erature is the temperature set values and the difference to the SCR trigger circuit heating thermostat control. 2.1 The use of Pro / E to establish mold standard parts library Family Pro/E is part of the family table (or assembly, or the characteristics of) a collection of these parts (or assembly o
22、r characteristics) are broadly similar, but in 12 some small differences, for example, fastening screws Hexagon many kinds of specifications, but they seem to be like and to implement the same function, so in the Pro / E in them as a part family is a very useful table in the family the same as a tab
23、le-driven components parts to be identified. In Pro / E use group table has the following advantages: 1) simple and compact to create and store a large number of objects. 2) For the generation of standard parts to save a great deal of time and work. 3) parts from a series of documents to generate change, do not have to re-create and generate for each part. 4) In the parts to create tiny changes in the relationship do not have to use to change the model.
