# How to Make the Frequency Converter Run at the Frequency When the Frequency Is Written on the Touch Screen

(source: Rongji igniter)

The touch screen is a man-machine interface. Our commonly used mobile phone input is also a touch screen, which is a capacitive screen. When fingers massage the touch screen interface, there will be a change in capacitance, and the chip in the mobile phone will sense this change and convert it into a voltage signal, that is, a standard analog quantity (if a point is a switching value, the switching value can be regarded as a special analog value), and then read it through the single chip microcomputer for easy processing, which represents some information. Generally, the resistance screen is used in industry, and the reason is similar.

Whether it's resistance, capacitance or even ultrasonic waves, they are just an induction medium. They are installed on the outermost side of the touch screen, which is called the touch panel. There is also a layer of glass inside, which is used for display, called liquid crystal. The two are separated. When the finger touches the touch panel, the industrial touch screen senses a certain amount of resistance. If it's just a point, it's OK Directly output a switching value to the single chip microcomputer. The single chip microcomputer has drawn up a standard, and you will know what action significance you require it to perform.

Similarly, you can also output an analog quantity on the touch screen interface, which can be regarded as a multi-channel resistance signal, that is, it represents the output of a group of continuous analog quantity modes to the single chip microcomputer, and then quantified into multi-channel switching quantity. Generally, the accuracy is poor. For example, you can use 8-bit switching quantity to represent an analog quantity. The frequency of the frequency converter you said is generally 0-50Hz, while 8-bit on The closing value corresponds to 0-255 (2 ^ 8) For example, 00000001 represents 1Hz, 00000011 represents 3Hz, 00001111 represents 15Hz, and so on. Each frequency value has a digital quantity corresponding to it. This process is the so-called coding, because the single chip microcomputer only knows the binary code, it is necessary to quantify the analog quantity in decimal system into 01 binary code, and each code corresponds to a unique physical meaning.

When you output 15Hz to the touch screen, the touch screen actually stores an 8-bit binary code such as 00001111. Then this code is stored in the register on the circuit. Then, to transmit this code to the frequency converter, the touch screen needs to be completed through some communication protocols, such as 485 and 232 at the bottom. This What are these communication protocols? They can be simply understood as a transmission and "translation process".For example, if you are Chinese and want to communicate with an American, you speak Chinese and Americans speak English, but each word referred to will have a corresponding standard. If you set such a standard, you can understand each other. For example, the Chinese "morning" corresponds to the English "morning". So you say the Chinese "morning" When the translator hears it, he will say it as the corresponding English "morning" to the Americans.

The 15Hz of the touch screen should be transmitted to the frequency converter. In fact, it is to transmit the 8-bit data such as 00001111 of the touch screen to the frequency converter. The 01 code is essentially a pulse. From the perspective of the circuit, as long as there are two lines, one high level and one low level, so that the pulses can be sent one by one in a certain order. If you want to transmit faster, improve the pulse accuracy The frequency, that is, the baud rate and other parameters can be set. The data sent each time is a series of pulses in a group, which is a "frame". After sending one "frame", stop a little and send another "frame" Of course, in the process of transmission, it is also necessary to let the other party know what type of data this is and consider the data reliability. Therefore, some start bits, stop bits, check bits, etc. are required, because in the data sent at one time, the data is a little longer than the upper 8 bits, such as 10 bits.

In the design of the frequency converter, of course, these receiving circuits are also considered. Each time it receives a series of pulses, it will read it into its single chip microcomputer, and then judge the meaning and function of this data, that is, after translation, it knows what it means. Because in the touch screen, the frequency code is not necessarily 15Hz, which is 00001111, which is also It may be 00001100, so it needs to change it into the corresponding 00001100 first, and then adjust the PWM control IGBT module to perform the operation of this frequency.

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