Application of the hottest touch screen combined w

  • Detail

In recent years, with the continuous progress of microcomputer technology, people have higher and higher requirements for automatic control system. The use of modern automatic control technology plays a very important role in reducing labor intensity, ensuring project and product quality, accelerating construction speed, improving labor productivity and reducing production and construction costs. The application of touch screen combined with PLC in frequency conversion energy-saving system is an automatic control trend, because PLC itself has the characteristics of high operation speed, rich instructions, powerful functions, high reliability, convenient use, flexible programming, strong anti-interference ability, etc, The elongation of the touch part of the material can be above 1000%, and the screen (Human-Computer Interface) can be used when more process parameters require human-computer interaction, which greatly strengthens the function of the entire automatic control system

through the combination of touch screen and PLC, the target value (pressure, temperature, etc.) can be directly set in the touch screen, and the actual value (measured value of the sensor) can be compared and calculated through PLC, so as to directly send operation instructions (analog signals) to the variable frequency energy-saving system and adjust the output frequency of the inverter. It can monitor the actual value of the controlled system and multiple parameters in the frequency converter in real time, and realize the functions of alarm, recording and so on. The frequency conversion energy-saving system of general PLC Combined with the closed-loop regulation of the touch screen is shown in the figure below

2. Main hardware composition of the system

the system hardware is composed of programmable controller (including digital input/output module, analog input module), a touch screen, frequency converter, sensor and several electrical components. The descriptions of each part are as follows:

(1) PLC: select S-Series cpu224 of Siemens company (equipped with digital input/output module and analog input module). By receiving the switching value and analog value input, the switching value and analog value are output after processing to control the action of the relay. At the same time, it carries out real-time communication with the touch screen, provides data for the display of the touch screen, and processes the information sent by the touch screen

(2) the touch screen adopts Siemens mp370. Realize man-machine dialogue, carry out data transmission and exchange with PLC system, write the set parameters into PLC, and read the internal parameters of PLC, sensors and frequency converters into the touch screen, so as to realize the real-time monitoring of analog and digital quantities, the setting of target values and alarm records

(3) frequency converter: Siemens 440 series is adopted, and its internal parameters can be set by the touch screen through PLC through uss4 protocol. According to the data (analog quantity) value sent by the PLC metal tensile testing machine specially designed for this purpose, the speed of the water pump or fan is adjusted, and its internal operating parameters are fed back to PLC and touch screen

(4) pressure, temperature and other sensors: convert the actual parameter values of the controlled system (water system or air system) into electrical signals and upload them to PLC and touch screen

(5) electrical components: supply power to PLC, touch screen, frequency converter and sensor to complete various operations and drives

3. Touch screen features and functions

touch screen monitor is a new programmable terminal that appeared in the 1990s and a new generation of high-tech human-computer interface products. It is suitable for application in harsh industrial environment. As a man-machine interface, it can replace ordinary or industrial computers. It has the characteristics of good interaction, high reliability, simple programming, simple connection with PLC and so on. The main functions of the touch screen are:

(1) it is mainly used to display real-time information about the operating status of the device or system in real time

(2) the touch button on the touch screen can generate corresponding switch signals, digital signals (numerical values) and characters to PLC for data exchange, so as to generate the operation of corresponding action control system or equipment

after the above items are confirmed (3) multiple pictures can be overlapped or switched to display graphics, strings, alarm information, historical records, trend charts, etc

4. The role of PLC in the system

plc, as a control unit, is the control core of the whole system. By receiving the switching value and analog value input, the switching value and analog value are output after processing to control the actions of relays, frequency converters and solenoid valves, which mainly reflect the following aspects:

1) initialize variables, set free communication port protocols and interrupt protocols

2) communicate with the touch screen in real time, provide data for the display of the touch screen, and process the information input by the touch screen

3) complete the mutual conversion of digital quantity and analog quantity

4) logic control and PID operation

5) send analog (digital) signals to adjust the output frequency of the frequency converter

6) read and write the internal parameters of the frequency converter through uss4 protocol

7) misjudge and transmit data information, alarm information, etc

5. Touch screen image design

the touch screen image is designed by special software such as protool, and then downloaded from the support tool (personal computer) to the touch screen for use. The total number of touch screen pictures shall be within the allowable range of its storage space, and the pictures shall be able to switch with each other and forcibly as far as possible

(1) design of main screen

on the support tool, create a welcome page or the controlled main system screen as the main screen, and the screen will enter into each sub screen. Each sub screen can return to the main screen in one step. If the picture of the controlled main system is taken as the main picture, some important parameters of the controlled system should be displayed in the picture, so that the whole controlled system can be concluded on this picture

(2) design of control picture

this kind of picture is mainly used to control the start and stop of the controlled equipment and display the internal parameters of the frequency converter. It can also be used to set the parameters of the frequency converter. The number of such pictures accounts for the most in the touch screen pictures, and the specific number of pictures is determined by the actual controlled equipment

(3) design of parameter setting page

this screen is mainly to set the internal parameters of the frequency converter, and it should also display the completion of parameter setting. Encryption should also be considered in the actual production

(4) design of real-time trend page

this screen displays the real-time status of the controlled value and the main working parameters of the frequency converter (such as output frequency) in the form of curve recording

(5) design of information recording page

this screen mainly records possible equipment damage, overload, value out of range, system emergency stop and other faults. In addition, the screen can also record the start and stop operations of each equipment as a voucher

(6) design of energy saving picture

this picture is mainly to record and display the cumulative power consumption and real-time power saving state of the frequency converter, so as to show the benefits of frequency conversion and energy saving to users, and can also be used to compare with other power saving measurements

6. Conclusion

the touch screen is used as a human-computer interaction tool in the frequency conversion energy-saving system, which is simple, intuitive and easy to operate; The whole frequency conversion energy-saving system and the hardware grade of the enterprise are improved. With the continuous development of microcomputer technology, the cost of touch screen itself is also constantly reducing. When combined with PLC in the system, the whole system has achieved a qualitative leap in actively leading enterprises to guide the healthy development of the industry in terms of scientific and technological progress and industry self-discipline without increasing the cost of system devices. This combination will be more applied in various production systems in the future, And become a highlight of the development of automatic control. (end)

Copyright © 2011 JIN SHI