外文翻譯---基于stm32的恒溫箱溫度控制系統(tǒng)(文件)
【正文】 16bit PWM output for great control accuracy. Fig 1 System control principle 3 hardware design This system includes temperature acquisition bridge circuit, STM32F103, color LCD touch screen control circuit, filtering circuit and SCR. In addition, the system has a good manmachine interaction function and can realize realtime monitoring and control by using inches color LCD and touch screen. Temperature control system structure is shown in . Fig 2 System structure temperature acquisition and A/D conversion Among the thermal resistance temperature sensors, platinum resistance, with advantage as high precision, stable performance, corrosion resistance and easy to use, is the ideal temperature acquisition ponent widely used in industrial environments and control systems. As the temperature acquisition range is 16℃ to 80℃ , Pt1000 is chosen as temperature sensor, which resistance changes with temperature according to certain rules and has good high precision and stable performance. Unbalanced bridge measurement is typical in detect circuits using platinum resistance as temperature sensors[1]. However, the nonlinearity between platinum resistance and temperature and nonlinearity of unbalanced bridge lead to acquisition error, thus we improved the temperature acquisition bridge circuit. Use constant current source to power the bridge, connect the two bridge arms with precise operational amplifier that is low noise and low temperature drift, use 4DH2 to constitute constant current source circuit which outputs A current, thus the current in platinum resistance is equal to constant current source. The ADC of STM32F103 is used to convert analog voltage of temperature into digital signal. The 12bit ADC is a successive approximation analogtodigital converter and has the function of selfcalibration. D/D conversion of each channel can be performed in single, continuous, scan or discontinuous mode, and in this system we use continuous mode. The result of ADC is stored in rightaligned 16bit data register which improves the conversion speed. In addition, the analog watchdog feature allows the application to detect if the input voltage goes outside the userdefined high or low thresholds. TM32F103 onchip resources TM32F103 can work in 40℃ ~105℃ and this meets the requirements of industrial environment. It incorporate the high performance ARM CortexM3 32bits RISC core operating at a 72 MHz frequency, high speed embedded memories (Flash memory up to 128Kbytes and SRAM up to 20Kbytes) to store data and program
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