The rationality analysis of the application of digital potentiometer in frequency converter

　　Instead of mechanical potentiometer, under the control of single chip microcomputer, not only can carry out simple manual frequency conversion speed regulation, but also can realize PID closed-loop automatic control according to the control requirements, which is a good way to control the inverter with a comprehensive single chip microcomputer.

　　It is necessary to understand the communication protocol of the inverter to control programming, and the software design of the digital potentiometer is complicated. Due to the different brands of inverter communication interfaces and communication protocols are different, there is no unified standard at present, and only one inverter can be developed, which reduces the selection range of inverter varieties, and the applicability is limited. For the analog input control mode, it can be supported in almost all inverter, although the function is relatively single, but can achieve the main function of speed regulation, can meet the requirements of most occasions, with universality.

　　The use of single-chip microcomputer control frequency converter CAN choose the latter two ways, the use of communication port control, its advantage is that the control function is comprehensive, through the corresponding level conversion circuit suitable for the frequency converter communication port form (RS484/RS232/CAN, etc.), you can communicate with the frequency converter, the hardware is simple, the number of connections between the two is small

　　At present, there is no unified standard, and only one inverter can be developed, which reduces the selection range of inverter varieties, and the applicability is limited. For the analog input control mode, it can be supported in almost all frequency converters, although the function is relatively single, application, rationality of digital potentiometer, analysis, but can achieve the main function of speed regulation, can meet the requirements of most occasions, with universality.

　　The most commonly used analog input speed regulation method is to adjust the frequency of the digital potentiometer by potentiometer, that is, to change the voltage value of the analog input to achieve the purpose of adjusting the speed. Although the use of mechanical potentiometer is simple and easy, but easy to wear, long-term use is not stable enough, and there is one of the biggest defects is only suitable for manual adjustment, can not achieve automatic adjustment. Use digital potentiometer instead

　　The use of digital potentiometer control frequency converter speed regulation, can be applied to various specifications of the inverter, the hardware composition is simple, does not need the high price of complex peripheral circuit D/A chip, under the control of the single chip can be closed loop automatic tracking adjustment, cost-effective, easy to achieve. Spray drying experimental machine is the liquid solution dry processing into solid powder, mostly used in medicine, food, chemical and laboratory sample preparation and experiments. In the experiment, it is required to choose different drying air volume and heating temperature according to the characteristics of the material

　　The most commonly used analog input speed regulation method is to adjust the frequency through the potentiometer, that is, to change the voltage value of the analog input to achieve the purpose of adjusting the speed. Although the use of mechanical potentiometer is simple and easy, but easy to wear, long-term use is not stable enough, while the application, rationality, analysis there is one of the biggest defects is only suitable for manual adjustment, can not achieve the application, rationality, analysis of automatic adjustment. Using digital potentiometer instead of mechanical potentiometer, under the control of single-chip microcomputer, digital potentiometer can not only carry out simple manual frequency conversion speed regulation, but also achieve PID closed-loop automatic control according to the control requirements, which is a good method for application, rationality and analysis of a comprehensive single-chip microcomputer control frequency converter.

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