基于PIC16C71的数字水温配制阀的设计

　　设计了一种基于PIC16C71单片机的数字水温配制阀。该配制阀采用NTC热敏电阻作温度传感器，与固定电阻组成简单分压电路作为水温测量电路，利用PIC16C71单片机内置的8位A/D转换器把热敏电阻上的模拟电压转换为数字量，PIC16C71单片机控制直流电机驱动混水阀调节冷热水的混合比例实现水温调节。给出了控制电路图，对水温测量电路的参数选择和测温精度作了详细讨论。实验和分析表明，选用阻值较大的NTC热敏电阻和分压电阻可较好地解决热敏电阻因功耗较大造成的热击穿问题。

　　Abstract:

　　A digital valve for controlling water temperature based on PIC16C71 was presented in this paper.A bleeder circuit which consisted of a NTC thermistor as temperature sensor and a fixed resistance was designed as water temperature measuring circuit.The analog voltage on the thermistor was converted into digital signal by a 8-bit A/D converter embedded in PIC16C71. Based on the digital signal， the MCU PIC16C71 drived the valve by a DC motor to adjust the water temperature through adjusting the proportion of hot water and cold water.The circuit diagram of controller was given，the principle，the component parameters and the accuracy of measuring temperatures were also dissertated in detail. It was found by experiment and analysis that thermal breakdown of thermistor caused by high power could be solved by selecting thermistor and fixed resistance with high impedance value.