Basic Knowledge of Inverters and Single-chipFrequency AC motor speed control used as the principal means have been used in a wide range of applications in the industrial area .It has a wide range of speed, steady speed and high precision, fast dynamic response for a wide range of technical performance and reliable operation has been gradually replace the DC motor speed control system. There are three main control types of inverter: first,through the operator panel inverter, that is, through the operation panel to change the output frequency and other operating parameters.Second, in the frequency converter analog input 0 10V or 4 20mA signal.Control the output frequency by changing the size of input analog converter.Third,control the communications port through the inverter.The first scene in general is used for manual adjustment and parameter settings,The latter two kinds of methods are mostly used for automatic regulation and remote control. Commonly PLC, DCS and other control systems in industrial area are applicable to the conditions of inverter interface control module,which can facilitate the realization of the closed-loop converter automatic control.They are more commonly used in large and medium-sized control systems. For some small experimental device and embedded control device, besides controlling the frequency converter, the processor generally also need to deal with keyboard input, display, data acquisition and other work such as process control.Such control is more suitable for single-chip control system as the core.When it comes to the PLC in the form of additional operating panel. It can achieve the function but the cost is too high,So it should not be used.Using single-chip control inverter can choose the last two kinds of methods.The advantage of the use of communication control full control function. By the appropriate level-shifting inverter circuit suitable for the form of communication ,then it can communicate with the inverter.The hardware is simple. The connection between them facilitate a small number of connections. The disadvantage is the need to understand the communication protocol converter in order to control the programming,and the software design is complex. As inverter for different brands of communication interfaces and communication protocols are different, there is no uniform standard can only be developed for a frequency converter,which reduces the choice varieties of frequency converter,and the applicability is limited. As for the analog input control, then almost all of the inverter can support.Although in more single function,it can achieve the main functions of the varies speed.And it can meet the use requirements of the majority of occasions,so it is universal.The most commonly used method of analog input speed is through potentiometer to adjust the frequency.That is, to change the analog input voltage value to achieve the purpose of speed regulation.Although the use of a mechanical potentiometer is simple, but easy to wear and has no enough long-term stability.Besides there is one of the greatest shortcomings is that it is only suitable for manual adjustment. Automatic adjustment can not be achieved.Digital Potentiometers used to replace mechanical potentiometers in single-chip control not only achieve simple VVVF manually, but also in accordance with PID closed-loop control to achieve automatic control.It can be regarded as a good way of a full-featured single-chip to control the inverter.Single-chip componentsIn addition to operation, single-chip also need complete control. Therefore, counting and timing can not be separated. As a result, single-chip is setted with the counter and timer settings. So far here, we already know the basic components of single-chip, that is, single-chip is setted by the CPU, read-only memory, read-write memory, input / output components and so on. In fact there is also a single-chip clock circuit, which during the operation and control of single-chip can be carried out rhythmically. In addition, there are the so-called interrupt system” janitors room.When the single-chip microcomputer to control the parameters of the object need to reach a certain state to intervene,then the janitors room can be communicated to the CPU.So that CPU in accordance with the priorities of external affairs to take appropriate counter-measures.Single-chip instruction set and assembly language programSingle-chip microcomputer has been described in front of the main component,these parts constitute single-chip hardware. The so-called hardware, is to see, can be touched and received. However, having such a hardware only means having the possibility of the realization of the calculation and control. Truly single-chip microcomputer to calculate and control can also be co-ordination of software. Software refers to various procedures. Only the correct procedure would be deposited in a variety of single-chip, it can work effectively