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SCM temperature control system in the industrial production structure and working principle of temperature control systems. Temperature is guaranteed by the change in temperature curve, without over-regulation or over-regulation of small, good stability, not shocks, Rapid modest nature of the system. On the following SCM resistance furnace temperature control system design and implementation. Temperature will transform to simulate thermal galvanic voltage, low-pass filter removes the interference signal amplifier evacuations, 0-5 V evacuation signal amplification to A / D conversion to digital converters sent MCU. Meanwhile, the cold spot temperature thermocouple temperature sensors into a voltage signal from the IC, then amplified and transformed SBC. Scaling transform degree temperature measurements obtained in accordance with the actual furnace temperature θ. Digital Controller under procedures set thermostats to the value of θ 0 errors Δ θ and θ. Integral separated by the PID control algorithm to control output volume Manuscripts. Digital Trigger uc control procedures under the conduction resistance furnace, the furnace temperature regulation changes to make it consistent with the duty to set thermostats.Conducting a long time, power output, temperature rises rapidly; Conducting a short time, the output power is a small temperature rises slowed. Temperature and temperature θ showed judgment procedures are completed time and temperature, with the temperature thermostats completed discrimination, - instructions for completing the warm voice signals. Dual Temperature Measurement value judgment procedures constantly under way to judge whether the temperature sensor that way, even given constantly alert signals. 2 thermocouple temperature sensor detection designs. Thermocouple sensor is inexpensive and high precision, simple structure, Measurement range (usually from-50 ～ 160 ° C) and the advantage of rapid response. Thermocouple sensor output voltage signals relatively weak (only a few tens of millivolt millivolt). Accordingly, before the need for signal conditioning Taking D conversion. The circuit by high magnification it magnified Taking D converter voltage level usually required level. Conditioning template thermocouple conditioning module normally used to complete this task or the most convenient and design, Instrumentation Amplifier also more difficult to produce more red tape to ensure accuracy.Figure 2 detection and amplification circuit temperature on the cold side should

adopt the use of thermocouple cold junction compensation sensor. When the thermocouple cold junction temperature is 0 ° C, the output will thermocouple cold junction temperature from 0 ° C figure, In order to improve accuracy and the need for cold junction compensation. Cold-detection circuit shown in figure 2. Cold Junction Compensation Compensation software can be used with IC thermocouple temperature sensors

In modern industrial production, current, voltage, temperature, pressure, flow, velocity and volume switches are commonly used parameters of the main accused. For example : in metallurgical industry, chemical industry, power engineering and paper industry, machinery manufacturing and food processing and many other fields. People need to have various types of furnace, heat treatment furnace, boiler, and the reactor temperature measurement and control. On the single-chip microcomputer to control the temperature is not only convenient control. simple and flexible configuration big advantages, it will greatly increase the temperature was charged with the technical indicators, thus can greatly enhance the quality and quantity of products. Therefore, the single-chip temperature control is a problem often encountered in industrial production problems. In this paper, it is carried out, and shared hopes to receive learned from the results.

Industrial temperature is the main target was charged with one parameter, as metallurgy, machinery, food processing, chemical industries, extensive use of the furnace, heat treatment furnace, reactors, strictly control the temperature of the workpiece. Computer control temperature control system temperature indicators have been greatly improved. Resistance Heater Control System Temperature Control Processes : SCM regularly to detect D chip on the corresponding digital conversion through computer data conversion, it should control the volume Power to control heating, the temperature control. System design should consider the following questions : Temperature change control Temperature temperature -- that is the scheduled time for a change, it is mainly considered in the design control process. Temperature control : If 400~1000 ° C, which involves temperature measurement device, furnace power choices. Control precision, over-regulation and other indicators, which involved D conversion accuracy and control law choice.

Hardware Design 1. Temperature detector and transmitter. ADC

temperature detector of choice and the choice of transmitter to consider the scope and accuracy of temperature control. 0~1000 ° C for the measurement using thermocouples, such as nickel chromium thermocouple, Graduation for the EU. 0~41.32mV output signals, millivolt transmitter output 0~10mA. -- then read current voltage conversion circuit voltage op. To improve the measurement accuracy of 0.1 for transmitter can be relocated. changed 400~1000 ° C temperature range, given 16.4~41.32mV thermocouple, Transmitter output 0~10mV so that the use of 8-bit ADC, quantization error of ± 2.34 ° C make. 2. Due to the expansion of the system interface chip to show both the police and keyboard input, but also control, Therefore, the expansion of the system in 8031 was 8,155, which has three eight Interface. 256 bytes of RAM can be used as an external data storage for the system. 8031 P2.1 accept the CE 8155, then 8155's P2.0 IO/M. When P2.1=0, P2.0=1, the three films selected 8,155 / port, port addresses are as follows :Register 0101H 0100H [] [] A state order mouth I 0103H 0102H [B] [C] I control the population register or low numerical terms eight 0105H 0104H [] [] high eight dollars and numerical methods Register When P2.2=0, selected ADCO8O9 (allowing access conversion and start reading the results of conversion). EOC signal conversion by the end of inverter followed disruption to the external MCU INT1 (P3.3). When P3.3=0, to translate the end. We will use as input channel 0, 0809 as a 03F8H address of the external data storage unit its written data, the WR 8031 and the START ALE signal so effective, 74LS373 latch the address will be deposited in three low 0809 and started ADCO8O9. D. 9EOC of low level, ongoing D conversion, switching to the EOC, said the end of conversion, 8031 can be read as good data conversion. 3. Temperature control circuit temperature control circuit Thyrister-way. Triac Series 50Hz AC power and heating wire in the circuit. If change thyristor switches in a given cycle time of the pulse signal can be connected. This can be one / line through export control procedures pulse.

To achieve zero trigger the end, AC zero-crossing detection circuit. 50Hz AC voltage corresponding to the circuit output pulse zero moment, as the simultaneous bidirectional thyristor trigger pulse, thyristor make the AC voltage zero conduction time. LM311 voltage comparator to 50HZ AC voltage into a square. Square, as the rising or

falling transition triggered monostable multivibrator signal Trigger pulse output stability of the single narrow door on the diode or mixed 220V power -- be it corresponds to the zero-crossing time synchronization pulse. This way as a trigger pulse synchronization pulse upon the temperature control circuit. SCM 8031 as a way of counting pulses added to the P3.4 and P3.5 input. (3) the laws and procedures designed to control the Resistance Heater Control is a feedback process Temperature and Temperature needs to be more practical deviation of the error signal processing controlled, The power to regulate the resistance furnace, the furnace temperature control to achieve.According to the error ratio, integral and differential have control (PID). process control is the most widely used form of a control. PID is the approximate difference equations using computers to achieve. PID law equation (abbreviated). Interrupt nesting mode using dual control system design process.

First make T0 Counter regularly interrupted, as the system's sampling period. D process started in a break in service, reading the data sampling, digital filtering, on the threshold alarm, PID, and then pulse output control signals. T1 pulse width counter overflow interrupted by the decision. T1 suspended pending, this sampling will be converted into the corresponding temperature display buffer. Then call display subroutine. T1 return from the suspension, then returned to the main program and suspended from T0, continue to show this sample temperature T0 waiting for the next interruption. Since 1976, Intel introduced the first batch of SCM, SCM technology into the 1980s, the period of rapid development in recent years, with the development of large-scale integrated circuits. SCM will continue rapid development of high-performance, four, 8-bit MCU to 16-bit and 32-bit MCU. SCM mainly used to control its application across the board, to the space shuttle, small refrigerators to daily life. color televisions, big MCU can display their talents. SCM in the three areas are very broad application : The first is household appliances industry, such as automatic washing machines, smart toys; Second, the communications industry, including telephone, cell phone and pager, etc.;The third is to create instrumentation and computer peripherals, such as floppy disks, hard disks, cash registers, meters. In addition to these traditional spheres, automobiles, electronics industry and foreign SCM application is a very broad field. It is low cost, high integration,